the issue

Transcription

the issue

highlights
a n e w s l e t t e r p u b l i s h e d b y s s pa s w e d e n a b 4 6 / 2 0 0 9
Photo: Ulf Sjöstedt
Contents
2 Comparative environmental performance analysis
3 Environmental focus demands Arctic operations
4 Economical gains through environmentally compatible ships
8 Green hydrodynamic design
10 Environmentally friendly transportation demands enhanced logistics
46/2009
I have a dream that the
maritime community will be
the most prosperous contributor fulfilling the climate
goals by the year 2050, with
good progress by the year
2020. Together we have the
potential to achieve this.
By factoring the perspective
of sustainability into ongoing
maritime business development, the community will
continue to be a major
supporter of globalisation,
providing international trade,
creating welfare and linking
cultures.
The ways forward
towards economical and
sustainable growth are many
and vary depending on the
role we play and the position taken.
Politicians and authorities are important players,
with great power and
resources and responsible
for developing the legal and
physical infrastructure in our
societies. The efficiency of a
door-to-door logistics services using sea transportation
is very much dependent on
a well-developed infrastructure – there remains a great
potential for improvement.
A step in the right
direction is the work performed within IMO, introducing goal-based standards
and paving the way for innovations not possible within
existing rules and regulations.
It is a challenge optimising the organisation, management and technical solutions
of complex systems such as
shipping . At a time when
world opinion is demanding change I believe great
innovations are waiting to
be discovered around the
corner, heading for the great
breakthrough, while minor
innovations will come as a
bonus on our way.
We are in motion but
we need to pick up speed
in order to fulfil our goals.
Together we can make it
happen.
Susanne Abrahamsson
2
Comparative environmental
performance analysis
A ship has systems onboard that is similar to a small
city. A number of machinery and devices are necessary
for the transport purpose. The indoor climate is to be
kept comfortable, drinking water must be produced,
sewage water must be treated, cargo requirements
such as humidity and temperature must be complied
with, and above this the “floating city” must be moved
from A to B within a certain time in almost all weather
conditions. The recent all-time high oil price together
with increasing environmental consideration put the
focus on energy saving and emission reduction from all
onboard systems.
A large amount of machinery is needed onboard for
all different kind of purposes, machinery that requires
energy, transforms energy or even gains energy from
outside the ship. The onboard energy can be divided into
mechanical, heat and electrical, where the ship’s propulsion is of course, representing the major consumer of
energy-mechanical energy. Lifecycle analysis indicates that
up to 90% of the lifetime energy consumption for a ship,
from steel plate production to scrap, originates from fuel
oil consumption during the ship’s operable period.
When, for example, the consumer buys a banana
and other tropical fruits in the shop, the transoceanic
transportation costs represent a significant proportion of
the price. In addition to the price, today’s consumers are
also becoming increasingly interested in the environmental aspects of the production and transportation of the
commodities that they are buying. For ship transportation
of tropical fruit there is an obvious relationship between
the transportation costs and the fuel consumption of the
ship and hence also a relationship between the use of
energy onboard the ship and the carbon footprint of the
banana in the shop.
In order to find out the consumed energy and produced emission for a typical route, SSPA has developed a
calculation model where all significant energy transformers onboard are considered. The model is to be used
to compare the transport energy efficiency and exhaust
emissions for different ships. The model can be used to
guide a ship owner on where to concentrate on fuel savings in his new building, optimize a existing vessels operation or indicate energy consumption. It also indicate how
much and what emissions are produced during transport
for the end consumer’s goods.
Björn Forsman, Peter Gylfe
46/2009
Increasing interest in natural resources located in
the Arctics puts demands
on environmental protection and conservation. Due
to the effects of climate
changes, ice conditions
in the high Arctic areas
are changing significantly.
Areas that were previously
remote and tough for
operations of any kind are
now opening up and providing access for seasonal
activities such as shipping
through the Northern Sea
Route and operations in
the Beaufort Sea, Canadian
Arctic and, Barents Sea
among other known areas.
T
he possibilities of
effective oil spill recovery at
sea as well as for shoreline
clean-up operations are significantly reduced when ice is
present at sea or along the
shoreline. ↓
Environmental focus demands
Arctic operations
PHOTO by courtesy of Transatlantic
Photo: Johannes Hüffmeier
High oil prices also support this growing interest in the
Arctic. Operators, oil companies and suppliers prepare
for well planned and intensive operations during short
summer seasons. Due to expressed environmental limits,
set by the environmental protection agencies in various
countries as the basis for operational and exploration
permission processes, all operators are being forced to
optimise all their activity plans for successful drilling or
exploitation campaigns.
Advanced environmental control programs and strict
limits are complied with through modern technology,
modern supply vessels and rigs, well planned operations
and actively choosing environmentally acceptable fuels.
SSPA provides operators with impact analyses and operational guidelines, based on risk analyses, in order to pro-
vide clients with cost effective and efficient recommendations on the optimised use of resources in all logistical
operations. These operations include towing and anchor
handling and other scheduled operations. SSPA is in a
position to provide clients with optimised operational
guidelines and optimised design support. Operations and
design go hand in hand, even in the Arctic.
Operational limits on footprints directly put demands
on safety aspects and expected out delivery capacity.
SSPA provides the Transatlantic Offshore and Icebreaking
fleet with risk based decision support services and
tools for dimensioning efficient services in high Arctic
Operations.
Jim Sandkvist
Upgrading Swedish spill
preparedness
The experience and know-how regarding efficient methods applicable in icy conditions are limited in Sweden
and are also recognised internationally as a problem
area associated with operational response gaps. In order
to update and strengthen its competence in this field,
the Swedish Rescue Services Agency (from 2009 the
Swedish Civil Contingencies Agency) commissioned SSPA
Sweden AB to conduct this literary research and to compile operational instructions to be added to an updated
issue of the existing operational field manual for shoreline
clean-up of oil spills in Sweden.
Manual clean-up methods will most likely continue
to be important for shoreline clean-up operations in the
wintertime in Sweden, but for potential large-scale shore
contaminations there is a need to develop the response
resources and to include additional mechanical recovery
equipment capable of operating from the shoreline of
ice infested coastal areas. Ice, snow and winter darkness make clean-up operations more difficult and unsafe
but the ice may also provide advantages with regard to
restricted spreading and to low ecological and socioeconomic sensitivity in wintertime. / Björn Forsman
PHOTO by courtesy of Swedish Civil Contingencies Agency
3
46/2009
Economical gains through
environmentally compatible ships
More than 90 percent of all external and more than
40 percent of the internal cargo transports in the
European Union are sea transports. Ships have the
lowest energy demand of all transport types per transported ton of goods. On the other hand, criticism is
directed towards the shipping industry for being a
source of pollution, and not working hard enough to
minimise the emissions from ships. In the ongoing discussion on climate change, the shipping industries must
therefore join forces both to minimise their environmental impact and to avoid the heaviest criticism. There
are also economic gains involved.
Choice of fuel
(MDO)
Efficiency
optimisation
of auxiliaries
Fleet planning
optimisation
Improved hull
maintenance
Voluntary
speed
reduction
Training and
education of
crew
Optimal rpm/
pitch combin.
setting (CPP)
Trim
optimisation
Route
optimisation
LOW
MEDIUM
HIGH
Implementation
Complexity or Costs
LOW
MEDIUM
Benefits for the
Ship Owner and for
the Environment
HIGH
E
xample of an ecological performance matrix for an existing ship. This matrix is
applied to a ship on a certain route and can look very different for other ship types, sizes,
cargoes and routes. The benefits can look different, for instance the position of trim and route
optimisation might be switched.
HIGH
Weight
considerations
Fuel cells
MEDIUM
Machinery
system
optimisation
Additional
propulsion
concepts
Hydrodynamic
optimisation
Eco-driving
Life cycle
analysis (LCA)
“Logistic”
design
LOW
Use of spill
heat from
engines
LOW
E
MEDIUM
HIGH
Benefits for the
Ship Owner and for
the Environment
xample of an ecological performance matrix for a ship at the planning stage.
This matrix describes some possibilities for reducing the environmental impact by for instance
machinery system analysis to get an optimal main driver – auxiliaries combination, optimised
logistic concept evaluating customer demands, additional propulsion concepts such as Kites,
and efficient design by identification of strategic key factors and LCA.
4
Improving performance
In recent years, there has been an extensive publication
of different measures and concepts, and their respective
increase in efficiency or reduction of emissions. It is often
difficult for the decision maker to decide on the concept
of choice. SSPA provides advice and suggestions to ship
owners on how to improve the environmental performance of ships in operation and on the construction of
new ships.
The fact is that all ships can improve their environmental performance. An environmental analysis and
optimisation of a single ship or the whole fleet of ships in
service, as well as new ships, can often lead to solutions
that are not only good for the environment but also cost
effective.
The ecological performance matrix
The different solutions available for environmental
improvements of ships can be classified into an ecological performance matrix, showing the cost effectiveness
of different measures. The complexity of implementation
implies a cost for the ship owner, while the benefits for
the environment are often connected to a reduction of
the operational costs.
Global warming and environmental
effects
Implementation
Complexity or Costs
SSPA currently manages several environmental projects.
Our role is to advise stakeholders in the maritime sector
and provide environmentally compatible improvements
and solutions. Caught by the spell of the myth that these
solutions imply extra costs, SSPA has shown, from many
years of experience of environmental issues within the
maritime industry, that the opposite is very likely to be
true.
Emissions of carbon dioxide is the primary source of
global warming. About 30 % of the carbon dioxide emissions come from the transport sector. Shipping forms
a relatively small proportion of these emissions (about
1.8 % – 3.5%) but shipping has an impact on many other
aspects of the environment.
Human health is affected by many of the substances
found in the emissions, such as particulate matter (PM),
ozone, volatile organic compounds (VOCs) and nitrogen
oxides (NOx). Exposure to such substances can lead to
severe public health problems.
The local environment is also damaged by ship emissions; trees, plants and also buildings and materials can be
affected.
Some examples of environmental impact from shipping are listed below. See also picture on the right.
• Ecosystems and freshwater quality are affected by acid
rain which comes from emissions of sulphur and nitrogen oxides.
46/2009
Impact of:
Newbuilding
Reparation
Ship break-up
Emissions
E
nvironmental impact of the shipping industry.
The discussion today are
mainly about the emissions to
air from ships.The emissions
include:
• Carbon dioxide (CO2)
– global warming
• Sulphur oxides (SOx )
– acid rain
• Nitrogen oxides (NOx )
– ozone layer
• Volatile Organic Compounds
(VOCs) – damage to soil and
groundwater, air pollution
• P articulate matter (PM)
– asthma, lung cancer, cardiovascular issues, and premature
death.
Noise
Radiation
Impact from
the harbour
Impact of:
Fuel/Lubricants
production
Dredging
(damage to marine
environment)
Propeller
erosion
Wake wash
Oil pollution
(Operation/
Accident)
Waste
Chemicals
Sewage
Noise
Biocide TBT
(Toxicity)
Ballast water
(Decreased biodiversity from
invasion of new species)
ILLUSTRATION: Ulf Johansson
• Marine ecosystems and coastal zones are affected by
the pollution of water by waste and intentional or
accidental oil spills, due to low safety levels and bad
procedures.
• The habitats of animals and plants may be destroyed
by emissions of biocides from the antifouling paint of
the hull.
• Ballast water often contains species of animals that
originate from the point of departure. When introduced in new areas, these species could thrive and
become a threat to other indigenous species and the
ecosystem.
• Finally, the air quality locally, regionally and globally is
degraded by the air pollution from ship emissions.
Towards sustainable shipping
The environmental improvements can be categorised
into different groups. Some of them are only feasible in
the planning and design phase of new ships, for example
the optimum choice of hull dimensions, hull and propeller
design and integrated energy saving devices. Others, like
the implementation of environmental strategies of the
shipowners or the optimisation of the HVAC (heating
ventilation air-conditioning) system, can be implemented
during the operational phase, and can help reduce the
environmental impact of the ship.
Many stakeholders are involved in the process of
reducing the environmental impact of the ship and keeping down the costs of transport. Below is a list of possible stakeholders and the influence each of them has on
all stages of the ship’s life. On the next page, this list is
illustrated.
• The ship yard and ship designer developing efficient
environmentally compatible ships;
• the ordering customer willing to invest in ships that are
more environmentally compatible;
• the ship owner using environmental strategies to operate the ship in a cost effective manner;
• the ship charterer or logistics company setting conditions for the performance of the ship (e.g. bunker
quality) including intermodal transport systems and
allowing for more flexible contracts;
• the ports improving their infrastructures and preconditions;
• the authorities helping the shipping industry with guidance, regulations and research, and thus assisting in
keeping shipping the environmentally friendliest mode
of transportation;
• the customer buying the products transported by
ships, and making environmental demands of the
producer, the transporter and all other stakeholders
involved in the production and the transport chain.
With greener transport the competitiveness and efficiency of ships increase and this has a positive impact on the
whole maritime industry. There are many techniques and
possibilities available to make a transport concept more
environmentally compatible but these may not be applicable to each and every project. On the way to cleaner
ships, SSPA is, therefore, able to assist all stakeholders to
analyse ship performances and to find the optimum solution for every specific transport concept or operation.
Johannes Hüffmeier, Jessica Johansson, Ulrika Roupé
5
46/2009
P
ossible measures to improve
efficiency and environmental performance
– Selection of SSPAs recent projects in
the specific field. The number given below
should not be added up to over 100% as
the possible gains are strongly dependent
on the ship, the ship owner, the transport
route, the logistic concept, etc. The measures often include several aspects of the
ship transport system.
Emissions/ Waste disposal
• Air cleaning measures in the
combustion system
• Exhaust filter, catalytic converter
• Sea Water Scrubbing
• Bilge water cleaning
• Ballast water treatment
• Noise emission reduction
Selection of SSPA projects:
• Environmental performance
monitoring and assessment tool
for Waxholmsbolaget
• “SPREEX: Spill Response
Experience”
• Icebreaker Oden
• Discharges of sewage and grey
water from passenger ships in
the Baltic Sea area
• “MARTOB: Onboard treatment
of ballast water (technologies
development and applications)”
• “TRESHIP: Technologies for
Reduced Environmental Impact
from Ships”.
Concept development and
engineering
• Systems engineering
• Engineering with regards to Life
cycle cost/energy consumption
• Ship equipment
• RPM steered pumps
• Optimisation of the gearboxes
• Heating of bunker
• Illumination by LED or low-energy lamps
• Reduction of emissions by different means
• Concept development of numerous ships
Operation of ships
• Eco-driving
• Route optimisation (weather routing)
• Trim/ ballast water optimisation
• Optimal use of thrusters/ tug boats
• Performance monitoring
• Fuel management
• Optimised Autopilot
• “eTEN WINGS”
• Trim optimisation studies
• Optimisation of berthing and manoeuvring in harbours
• Energy and emission prediction of ships
• Automatic Identification System (AIS)
• Environmental impact of icebreakers in
Arctic waters
• Measures for a more environmental friendly shipping
• Life cycle analysis (LCA)
Marketing/ PR
Operation of ships
~20%
Emissions/
Waste disposal
~15%
Concept and
system engineering
~15%
Optimal propulsion
system
~20%
Optimal propulsion system
• New concepts for propulsion,
sources of additional thrust
(Rotors, Sails, Kites, Solar cells)
• Suitable main engine type and efficiency
• Reduction of propeller axis losses
• Optimisation of steering system
• Feasibility study “Flettner rotors as
propulsion support”
• “OPTIPOD: OPTImal design and
implementation of azimuthing
PODs for the safe and efficient
propulsion of ships”
• Leading Edge
• FASTPOD
6
Marketing/ PR
• Presentation as market leader within green shipping
• Consequent marketing of new solutions, concepts
and ideas
• Strategic research
• Inventory of today’s performance
Energy-efficiency
~20%
Energy-efficiency
• Procedures for use of energy on ships – awareness
• Weight saving with regards to choice of light materials and equipment
• Weight saving with regards to strength calculation
(FE-Analyses) and structure optimisation
• Energy onboard: optimised systems/complements
(auxiliary machinery, waste heat boiler, cooling
water, HVAC, hydraulic and piping)
• “LÄSS: Light weight marine constructions”
• “EFFISES: Energy efficient safe innovative fast ships
and vessels”
• “Design tool for energy efficient ships”.
• ”Pre-study of new construction materials concepts
for construction of ships with low energy consumption”
• New methods for using energy in cooling water
Management of ships
• Route planning
• Utilisation of capacities
• Procedures for operating the ship – Crew training
• Life cycle analysis
• Voluntary Speed Reduction
• Effective maintenance planning
• Environmental assessment
• Operation at a high safety level
46/2009
Port operation / logistics
• Improved cargo handling in ports
– turn-around time in port
• Use of shore sided
electricity/”Cold ironing”
• Improved cargo storage and
loading/unloading
• Heating or cooling of cargo e.g.
insulation and heat exchanger
• Ice-reducing measures in
Swedish harbours
• Port waste management –
reception facilities for ship
generated waste
• Transportation of oil in the
Baltic Sea Area
Port operation/
logistics
~15%
• “SAFEDOR: Design, operation and regulation for safety”
• “SEALOC: Transport of Dangerous Goods”
• “CA FSEA: Concerted Action on Formal Safety and
Environmental Assessment of Ship Operations”.
• Environmental management system design for naval
vessels
• Soft bottoms in Swedish water
• Environmental impact from wake wash of large and fast
crafts
• "TOSC: Transatlantic optimum service concept"
Management
of ships
~25%
Intermodal
transport
~10%
Intermodal transport
• Optimisation of the
transport chain/ multi-/
intermodal transport
• Cooperation with other
transport and logistic
companies
New energy
systems
~30%
Use of
chemicals
~10 %
Hydrodynamic
design of ships
~20%
• Efficient public transport
by ships
• INTEGRATION
New energy systems
• Solar cells for heating of water and power production
• Choice of fuel type/ alternative fuels
• Using alternative energy systems ( wind and solar
energy, bio fuels, LNG, fuel cells, El batteries for propulsion and other energy demands onboard.
Use of chemicals
• Choice of antifouling
• Minimised use of chemicals/
cleaning agents
• Use of alternative chemicals/
cleaning agents
Hydrodynamic design of ships
• Optimum choice of hull parameters
• Hull design optimisation
• Propeller efficiency/ propeller design
• Hull appendices/ fuel saving devices
• Optimised air resistance
• MAGALOG – LNG as a fuel option
• New energy systems for ships
• Shuttle powered by modern technology
• VRS-ropax
Selection of SSPA project
• Consequences of restricted
use of organic tin compounds
for shipping in the Baltic Sea
and the North Sea
• AIS43
• MASTEC
• >6000 hull forms developed and
tested at SSPA
• Virtue
• “FANTASTIC: Functional design
and optimisation of ship hull forms”
• “SMOOTH: Sustainable methods
for optimal design and operation of
ships with air lubricated hulls”
7
46/2009
Green hydrodynamic design
In order to minimise all harmful pollution from a ship
affecting the climate, the first priority should be to
reduce the fuel consumption. That is not a new idea,
but when thinking in terms of green design, some old
routines have to be changed to reach new goals, e.g.
not only how to optimise the ship’s hull and propeller, but also how to face the logistics of sea transport
when moving cargo from one point to another. A thorough investigation of the shipping is needed, of which
the ship size and speed constitute only one element.
Environmentally friendly hulls
As part of the initial estimate, the main parameters of
the ship have to be considered. The length, draught and/
or width of the ship is often governed by the fairways
and ports the ship is expected to approach, but by challenging today’s restrictions, major gains can be achieved
using more optimal main parameters. Sea conditions
and wave directions on the expected routes are also to
be considered, not just performance in calm water. The
design should take into account service conditions!
In order to be able to achieve more environmentally
friendly designs, there should be greater freedom for
the hull designer to change the main dimensions (within
reasonable limits) without significantly losing displacement
or cargo volume. Considerable gains are possible. See
the figure at the bottom of this page. In order to maximise the gains and minimise the costs, it is important to
involve the hydrodynamic expertise at an early stage. This
extra effort and cost will pay off easily, in terms of both
the environment and also the financial gains.
The SSPA data bank reveals
A
typical twin skeg
hull form with well balanced
skegs reduce power consumption by taking advantage of
the balance between pre-rotation, resistance and propulsion
efficiency.
With the best main parameters identified the real hydrodynamic design can start, where the hull form and the
propulsor can be optimised. Looking at statistics at SSPA,
the spread in fuel consumption for a certain type and
size of ship may be of the magnitude of 20 % or more.
The data bank at SSPA consists of more than 6000
tested ship hull forms. Some of these designs have obvi-
Examples of previous case studies about
green shipping:
2008/2 When MAX becomes more than Max
2007/3Early hull optimization lowers greenhouse
gas emissions
2007/3The quest for lower fuel costs - save by
improving wake quality
2007/3Bureaucracy– a serious obstacle in Short
Sea Shipping
2006/2Lightweight construction increases transport efficiency
2006/2 Utilising pre-swirl flow reducing fuel costs
2006/2Preparing for a major oil spill in the Baltic
Sea
2006/2 Coastal Hazards and Management
2005/3 Multihull performance for the North Sea
2005/3More insight into propeller performance
with CFD
2005/3 A fast Ropax ship for the future?
2005/2It takes two skegs to increase cargo
capacity
2005/1Frictional effects from bio-fouling and
coatings
2004/3 Appendages for high-performance ships –
testing for design
2004/3 LNG transports - Risk assessment and
operational analysis
2004/3 A total grip on sea surveillance
2004/3 Effiecient, safe and environment friendly
shipping in the Baltic
2004/2 Very Large interest in Crude Carriers
2004/1 High-speed port for high-speed craft
2003/3Streets clogged up? Reclaim the waterways!
2003/2Stopping the alien invasion: Ballast water
treatment
2003/2LNG – Future market demands provide
future challenges
2003/1 Predicting wake wash
2001/3Safer fairways – a project with environmental implications
2001/1Ship, train, or truck transport – which is the
greenest?
ously not been optimised prior to testing, resulting in a
20 % higher fuel consumption compared to the best of
their type and size.
Twin skeg hull – a green solution
For decades SSPA has advocated the twin skeg hull without saying that all ships should be of this kind. However,
there are some obvious green benefits included in this
concept:
• To go from one propeller to two can often give a
more optimised propeller design. As well as obtaining a
higher propeller efficiency, noise and vibrations can also
be kept lower, which is in line with green thinking.
8
46/2009
Green hydrodynamic design
• Of all the hull configurations tested at SSPA, more
than 400 have been twin skeg hulls. It can be seen that,
among the full hull forms there is an average of 2–3 %
in power reduction for the twin skeg ships compared
to the best single screw ones when all data is studied.
If draught restrictions arise the difference may be much
bigger.
• The twin skeg concept allows a comparatively more aft
located centre of buoyancy, which enables a slenderer
fore body with less hull resistance.
• By placing the engines partly in the skegs, shorter
engine rooms or longer cargo holds can be achieved,
which may increase ship transport efficiency.
Propulsive Power
Design draught. Sea condition
S
Beam
howing the large
differences in power that can
be achived by an early parametric hull study.
• Two propellers mean propulsion redundancy, and that
is definitely a green approach. Completely separate
engine rooms further contribute towards redundancy.
With a twin propeller arrangement, there are considerably greater chances of avoiding water pollution due
to grounding or collisions if one propeller stops.
• The twin skeg concept, having two rudders, normally
increases the maneuverability, which also leads to a
safer and thereby greener ship. At the same time the
two skegs normally provide a good course stability,
which not only has a safety aspect but is also beneficial
for the fuel consumption – especially for fuller hull
forms.
T
he trim optimization gives information about
operating the ship in the most
favorable trim condition. In realistic operation conditions it is
possible to gain about 1–6%,
and occasionally even more.
Vs = 21 knots
Curves of constant ship displacement x 103 [ton]
17
16
Not all ships benefit from being of the twin skeg type.
Very slender ships seldom benefit from the twin skeg
form, except for the fact that the redundancy in having
two propellers is, as previously mentioned, a greener
solution. Sometimes the slender ships need to have twin
screws if the draught is restricted. Then it must be considered whether the twin skeg hull form will be better
than the conventional twin screw ship. SSPA has developed successful twin skeg designs down to block coefficients of 0.58.
To find the last tenth of one per cent
Regardless of the type of hull form, the final optimisation
of the ship hull lines is where the last percentages of fuel
reduction can be achieved. At SSPA, the design process
based on the database and experience is supported by
CFD programs such as SHIPFLOW. For further optimisation of a hull shape, SSPA also use the fully automatic
optimisation routines (parametric CAD/deformation
boxes, optimiser and CFD). This loop can be executed
with potential flow for fore body optimisation or a fully
viscous solver for aft body optimisation. Even where the
design may appear fully optimised, one can ask if there
are further possibilities of improving the efficiency by
using different fuel saving devices. The green hydrodynamic design must, therefore, consider all possibilities in
order to minimise the fuel consumption to the very last
tenth of a per cent.
Power PDT [MW]
15
Optimum trim
14
13
12
–2.5
–2
–1.5
–1
–0,5
0
0,5
Trim [m]
aft trim < 0, forward trim > 0
1
1.5
2
2.5
The way the hull runs (trim and draught) can imply
considerable bunker variations. Onboard optimisation
measurements have to be corrected for subjective
human observations of the environmental conditions. The
relevant data for making the corrections are not always
available. Together, this limits accuracy. Model tests under
controlled conditions remove much of the ambiguity.
SSPA carries out many trim-draught investigations – covering the complete loading range of a hull. Such a study
is a cost-effective, low-risk way of saving from 1% to 6%
on fuel costs (occasionally even more) which is normally
paid off within a year in the case of a single ship and
within a few months if there are sister ships.
Björn Allenström, Lars Gustafsson
9
46/2009
Environmentally friendly transportation demands enhanced logistics
Today, around 40 per cent of the
transportation of goods within
the EU. is done by ships. Even
though market development
for short sea shipping in recent
years has faced some challenges,
for example the construction
of fixed links, new regulations,
and a dramatic increase in the
price of fuel, waterborne goods
transportation within Europe has
increased over the last few years.
This is good from an environmental point of view but could
be better – from a global perspective. With the globalisation
of economic activity an overall
increased share of transportation on keel would be desirable.
The revitalisation in short sea
shipping has been caused by
technological developments, the
growth in trade, and greater
integration of functions along the
supply chain and is a response
to congestion, environmental
concerns, and other issues affecting contiguous land transport
networks. Shipping also requires
efficient ports that need to
provide connectivity in terms of
appropriate facilities and to bridge
the gaps between the modes in
regard to frequency, capacity and
time. SSPA has experience from
a number of research projects
and consultancy assignments in
port development and design.
Efforts are often directed towards
improved safety, increased efficiency of operations and the
reduction in environmental impact
caused by the port’s activities.
10
A
n ongoing project at SSPA is the research study
into the utilisation of the capacity of container feeders. Enhancements in the utilisation of vessel capacity will not only
result in significant improvements in financial results for the
shipping company, but could also make it possible to reduce
the environmental impact caused by the transport industry.
The relationship between environmental concerns and transport efficiency is, therefore, an interesting research field. Later
this year, Linda Styhre, doctor candidate at SSPA, will present
her doctor’s thesis about the enhancement of the utilisation of
vessel capacity in short sea shipping.
PHOTO © Shutterstock
Photo: Port of Helsingborg
T
he port of Helsingborg intends to increase its container volumes and also to improve its logistics infrastructure
in the port area. For this purpose, larger berths and more efficient use of the land area are essential. According to the port,
the process could be divided into three steps:
1 The access to the port from sea;
2 The lay-out of the berth and back-land;
3 The connection between the port and land infrastructure
A
s a consequence of increasing transport volumes by
sea, many ports need additional capacity. Increased capacity can
be achieved by better utilisation of resources or by physical expansion of storage spaces, marshalling areas and quays. However,
since many ports are located in cities or other densely populated
regions, they do not have the land to expand their terminals. This
situation calls for a focus on resource utilisation. One example of
this is the Värtan, which is located close to the heart of Stockholm
and is an important link carrying considerable flows of goods and
passengers to various destinations in the Baltic Sea area. SSPA
identified a wide variety of solutions for improving safety as well as
ensuring efficient cargo and passenger handling within the terminal area. Improved safety for people working in the terminal was
given a high priority. The proximity to residential areas of the city
also implies stringent environmental demands and restrictions in
particular with respect to noise and emissions from the port operation and associated traffic.
The further planning and development of the port is dependant on how the future harbour will be designed so as, to ensure
a safe approach from the sea. As a starting point, the port has
investigated several different general arrangements for the docks.
In this process, SSPA has so far supported the port from a nautical point of view. The next thing to do is normally to simulate
ship-movements, either in a desk-top or a full-mission simulator.
When the design of the docks and the berths is finally decided, it
is time to continue with the remaining two steps in the process.
46/2009
Env onmen a y
1/2003
1/2003
Predicting wake wash
B
jörn Forsman,
Project Manager, M. Sc. in
Mechanical Engineering, graduated from Chalmers University of Technology in 1979. In
1980 he joined SSPA where
he has worked with development of oil spill recovery
equipment, arctic offshore
engineering, model testing and
simulation of ship manoeuvring, and has been responsible
for leading and co-ordinating
commercial projects in the
area of marine environment.
He has also been programme
manager for a number of
advanced international and
regional training programmes
on Coastal and Marine Environment Pollution Prevention
and Maritime Safety Management.
Telephone: +46 - 31 7729059
E-mail: [email protected]
Which waves are important?
Three different wake wash components were analysed in
the project.
– The Bernoulli waves: the formation of the water surface around the vessel hull due to the pressure distribution in the water around it.
– The Kelvin waves: the pattern consisting of divergent
and transverse waves, and the corresponding pattern in
shallow water.
– The solitary wave: a single wave that is sometimes
generated and that travels ahead of the vessel.
It was concluded that Kelvin and Bernoulli waves are
important for safety and shoreline erosion in archipelagos,
while solitary waves probably are not.
1/2005
Kelvin waves
When a vessel is moving through water, it generates
wake wash, i.e. waves and other water motions. There
is a risk that the wake wash causes environmental and/
or safety problems. Special attention has been directed
towards the wake wash from high-speed ferries, since it
has caused accidents resulting in injured people or
damaged boats etc. The wake wash from high-speed
ferries is also suspected to cause additional shoreline
erosion. The wake wash generated by large displacement vessels, such as conventional ferries, also causes
environmental impacts.
SSPA was coordinator for an interdisciplinary research
project where wake wash components were analysed
and numerically modelled. The project participants (SSPA,
SMHI, WET, WRE) represented several different disciplines, which is an advantage in a project with such an
extensive purpose. The project was focused on two types
of vessels: large vessels and high-speed vessels, respectively. A typical example of a large vessel is a conventional
Ropax ferry with a length of about 200 metres and a
travel speed of about 20 knots. A typical example of a
high-speed vessel is a high-speed ferry with a length of
about 100 metres and a travel speed of about 40 knots.
Other vessels, similar to the ferries described, were also
studied by this project.
end y anspo a on demands enhanced og s cs
J
W
ake wash generated by high-speed vessels in deep
water may cause problems when reaching shallow nearshore waters.
PHOTO: CONNY WICKBERG
Bernoulli wave
That the Bernoulli wave can cause a large lowering of the
water level along the banks when the vessel is operating
in a canal, a so-called drawdown, is a well-known phenomenon. In the present project, it was found that the
Bernoulli wave can also cause a significant drawdown in
bays and other seemingly sheltered areas along the fairway, when a large vessel passes outside them. This drawdown can be a direct result of the vessel’s passage but it
might also be a result of the Bernoulli wave being scattered by e.g. an island outside the bay. It is also possible
for a seiche, i.e. a periodic variation of the water level, to
be generated in the bay. Shoreline effects of the drawdown vary depending on whether the shore has a mild or
a steep slope. Shoreline erosion on mildly sloping shores
will be negligible. On steep shores (banks), the temporarily lowered water level during drawdown causes outward
hydraulic pressure gradients that decrease the structural
stability of the bank resulting in erosion.
essica Johansson,
Project Manager at SSPA since
2002. She received her M.Sc.
degree in Mechanical Engineering in 1996 and her
Lic.Eng. degree in Environmental Sciences in 2001 from
Chalmers University of Technology. During her employment
at Chalmers she gained research experience in areas of
importance for a future sustainable society. At SSPA she
works with environmental related issues in the marine area.
Telephone: +46-31 772 9105
E-mail:
[email protected]
The appearance of Kelvin waves (and corresponding
waves in shallow water) is governed by the length, shape,
and speed of the vessel, and the water depth. Certain
combinations of these factors will result in maximum
wave generation. A special situation is when Kelvin waves
generated at high speeds in deep water reach shallow
water. The wavelength becomes shorter and the wave
amplitude increases as it approaches the shore. The sudden appearance of high waves along the shore may surprise people who are bathing or navigating small boats
nearshore. Kelvin waves can cause shoreline erosion or
accretion depending on the state of equilibrium of the
profile with the ambient wave conditions.
How to avoid problems
Instead of experiencing safety problems or shoreline
erosion due to large and high-speed vessels, it is desirable
to predict the possible problems before they occur by
using various modelling tools. Several different tools have
been developed or used in the project. Together they
cover all steps from vessel to shore. As drawdown is a
long period event, the long wave equation and the shallow water equations are suitable model equations, and
the vessel can be sufficiently represented by a simple
point source-sink pair. Details of drawdown at the shore
are modelled with an analytical and numerical model. The
Kelvin waves close to the vessel, i.e. in the near field, can
be predicted by SHIPFLOW. For simulation of the propagation and transformation of Kelvin waves, the SHIP-
– To investigate which components of the wake wash, i.e.
waves or other water movements, generated by large
and high-speed vessels operated in archipelagos, are
important for safety and shoreline erosion.
– To show how computer-modelling tools can be used to
describe the generation, propagation, and transformation
of such components, and the resulting shoreline erosion
caused by them.
M
Project participants
ichael leerandersen, project Manager
and ph.d. student at sspa. he
received his M.sc. in 1996
from the technical university of
denmark. he was employed at
sspa in 1997 as a researcher,
specialising in hull resistance
due to rough surfaces and
wash wave simulations using
CFd and measurements. he
has carried out several commercial and research projects
using CFd.
telephone: +46 - 31 772 9049
e-mail:
[email protected]
– SSPA Sweden AB (SSPA)
– Swedish Meteorological and Hydrological Institute
(SMHI)
– Water Environment Transport (WET) at Chalmers
University of Technology
– Department of Water Resources Engineering (WRE)
at Lund University
Financial support
– The Swedish Agency for Innovation Systems
(VINNOVA)
FLOW far-field model, the ray tracing model, and a Boussinesq-type model are suitable. It is possible to couple the
Boussinesq-type model for the far field with SHIPFLOW
for the near field. This approach gives an accurate prediction and should be further pursued. The shallow water
equations and Boussinesq-type equations are solved
numerically using high-order discontinuous Galerkin methods, giving computationally efficient models. The swash
hydrodynamics model describes the water movements at
the shore due to Kelvin waves. The resulting erosion due
to Kelvin waves is obtained by coupling the swash zone
sediment transport model or the analytical model for
dune or bank erosion to the swash hydrodynamics
model.
With the knowledge gained and the modelling tools
developed during this project, SSPA and the other project
participants are today well prepared to effectively tackle a
wide range of environmental and safety related wake
wash issues like
therefore “to decrease frictional resistance” the only
remaining viable option for an optimised hull shape
(except more specialised ships such as hover craft or
ses) is to modify the surface itself. A hydraulically smooth
surface is a surface which roughness is so small that no
further smoothing of the surface will benefit a frictional
decrease. but - almost no commercial or military ships,
even when newly built, have a hydraulically smooth
surface. the roughness of the steel plates and the roughness of the coating itself are too high, for which reason a
roughness allowance must be added to predict the total
resistance. Fouling and damage to the coating will further
increase the roughness allowance with time. therefore, it
is important to know how large effect the roughness has
on frictional resistance. to be able to investigate this ssPA
has devised different methods, both experimental and
computational.
Evaluating methods
skin friction on surfaces typically encountered on hull
surfaces, can be evaluated using several methods. the
simplest method would be to use empirical relations
linking the surface geometry to the skin friction, using
one or several parameters, as for example equivalent
sand roughness. the drawback of this approach is that
poor accuracy can be the result, if the rough surface
does not have a surface geometrically similar to measurements which the empirical model is based upon. CFd
(Computational Fluid dynamics) computations are also a
e
xample of full scale computation of the frictional resistance on the dyne tanker for a barnacle surface (top) and hydraulically smooth surface (bottom). red contour is the highest frictional
coefficient decreasing towards blue.
possibility, but is a difficult venue as the roughness more
often than not must be considered irregular in shape.
Measurements are the final option. several methods
can be used, such as Pipe flow, Flat plate flow, Cavitation
tank or Couette cell measurements. the first 3 methods
have been designed, built and tested at ssPA in recent
years, each with their unique advantages and disadvantages. the Pipe flow device has been used for measuring
friction coefficients for a number of different bio-fouled
surfaces, more specifically barnacles of different sizes and
densities, whereas the plate has been utilized for surfaces
with smaller added frictional resistance, such as newly
applied coatings requiring a higher accuracy of measurement. Cavitation tank measurements will not be covered
further.
ho o
ö n o
Comparing two different newly applied coatings requires
high accuracy as the difference must be expected to be
quite small. therefore, the ssPA Flat plate flow measurement device is used for those kinds of measurements in
the towing tank.
As an example a comparison of the frictional resistance for two similar self-polishing coatings, applied under
different conditions, is shown in the figure below. both
coatings are from market leading manufacturers and
were applied to the plate by the manufacturers them-
man
p
ipe friction measurement device for surfaces with
expected high increase in friction.
consistent with the difference in roughness. For a full
scale tanker the difference in resistance between the two
coatings will be approximately 1 percent, which is not a
trivial difference.
From measurements to full scale
increase in friction due to rough surfaces also changes
the boundary layer near the hull surface by decreasing
the flow velocity compared to a hydraulically smooth
surface. this is known as the velocity shift, and can be
utilized in connection with the measurements to simulate
the local skin friction on a hull surface using CFd. having
obtained the local full-scale friction, it is a small matter
to extract the total skin friction of the ship due to the
experimentally measured surface.
each surface is described using an average roughness
height and an efficiency number which are experimentally
obtained. Using this approach it is possible to scale the
roughness for geometrically similar surfaces.
h
Benefits
t
e
he sspa Flat plate
flow measurement
device in the towing
tank. the plate is 1m
deep and 6m long,
and is as thin as
practical to keep the
wave resistance as
low as possible.
M
xample of friction
measurement on two coatings.
residual resistance based on
measurements on hydraulically smooth plate has been
deducted from the measured
total resistance.
selves.
the roughness height of the coatings was measured
using a bMt roughness measurement device, and the
result was 76µm to 33µm for the first and second coating respectively. the higher velocities in the measurement
clearly indicate a correct behaviour of the measurements
and also detect a clear difference in friction coefficient,
Knowing the frictional effects of common surfaces on
hulls offers a number of possibilities: better estimate of
roughness allowance for full-scale prediction of total
resistance, monitoring of the hull surface as a decision
tool for timing of cleaning or recoating for resistance reasons, or finally as a tool to decide the economical advantage/disadvantage of using a better but more expensive
coating.
Michael leer-andersen
henrik andreasson
7
6
Plate Flow
For surfaces with a large increase in friction coefficient,
the pipe measurement device is sufficiently accurate. the
principle is simple. Water is forced through a pipe with a
known flow rate, coated or bio-fouled on the inside, and
the pressure drop due to the friction on the inside of the
pipe is used to obtain the friction coefficient.
odelling tools developed or used in
the project in order to describe generation, propagation, and transformation of wake wash components, and the resulting shoreline erosion caused
by them.
PHOTO: OLA JENNERSTEN,
NATURFOTOGRAFERNA
p
ipe flow measurements converted to full-scale
flow over a tanker for different
barnacle surfaces ranging
from a badly cleaned barnacle
surface to a densely barnacle
covered surface with a roughness height of approximately
4 mm. the lowest line is the
hydraulically smooth surface.
Pipe Flow
enrik andreasson
project Manager at sspa. he
received his M. sc. degree
in naval architecture 1999
at Chalmers university of
technology and has since then
been employed at sspa. he is
primarily working with model
tests and CFd calculations for
hull form optimisations.
telephone: +46 - 31 772 9072
e-mail: henrik.andreasson@
sspa.se
Björn Forsman/Jessica Johansson
T
Frictional effects from bio-fouling and coatings
Viscous resistance is the main resistance component
for most types of ships, ranging from about 50 percent
of the total resistance for high-speed craft to 90 percent for slow displacement ships such as tankers. The
significant part of the viscous resistance is the skin friction and to add to the misery, skin friction is difficult to
decrease by modifying hull shape as the most important
factors are wetted surface area and speed.
Purpose
– environmental impact assessment and permit processes
addressing vessel generated shoreline erosion,
– rulemaking with regard to speed limitations and guidelines for interaction with moored vessels and,
– port and fairway design with a minimum of wake wash
related interaction effects.
raffic with large vessels
in archipelagos can generate
wave interaction effects with
islands and irregular coast-line
topographies.
1/2005
Frictional effects from bio-fouling
and coatings
Namnlöst-2 4
5
S
07-02-07 22.37.46
Namnlöst-2 5
07-02-07 22.39.11
SPA ha o many yea been nvo ved n a numbe o d e en con u
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SSPA ha ecen y comp e ed a k ana y o S y öbo age on a c w h new
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E
2/2006
MySincereSeason’s
Greetings
to all of ssPA’s clients, partners and colleagues in the
maritime society.
thank you all for the
opportunities given and
confidence shown to us as
we worked together during 2006.
the near-term outlook
indicates that the global
economy will continue to
grow at a fast rate. this is
positive for the trade and
transport sectors, but stresses the need for efficient
resource utilisation.
in relative numbers the
shipping industry offers the
most energy efficient transport services but in absolute numbers the industry
is a major energy consumer.
however, in every complex
system, like shipping, there is
room for improvements. in
order to reduce energy consumption, different means are
available for the existing tonnage, ship conversions and
newbuildings.
technical innovations frequently enter the market,
like the ones described in
the articles “lightweight
construction increases transport efficiency” and “Utilising pre-swirl flow – reducing
fuel costs”. in the area of ship
management, development
work is being carried out in
areas such as advanced route
planning systems, and cargo
and ballast systems. the list
can be very long.
it is not only from an
economic perspective that
the efficient utilisation of
resources is beneficial. it is
also very significant from the
environmental perspective.
Preventive actions are today
regularly taken in order to
secure sustainable growth.
governments are introducing
and managing traffic control
systems in critical geographical areas, and the awareness
of environmental values is
spreading within the shipping
industry.
ssPA supports sustainable
growth.
International and national legislation will impose ever
more stringent requirements on marine transport. This,
together with the fact that fuel costs over a ship’s
lifetime have a decisive effect on its total life cycle
cost and its environmental impact, drives shipping
lines to constantly look for more efficient transport
systems. Lightweight construction of ships can thus
make a significant contribution to increasing the competitiveness of transport systems at sea.
since 2005, ssPA has been a part of the lÄss project,
lightweight Construction Applications at sea (www.
lass.nu), where the overall objective is to improve the
efficiency of marine transport. Development of four demonstration ship concepts, based on different ship types
and materials, is intended to point out the potential for
weight reduction, transport efficiency and environmental
performance.
Commercial factor talks
Advances in ship design and building are driven by
numerous factors of which the commercial factors are
the most influential. ship owners involved in the lÄss
project are able to reduce the weight and increase the
stability of their vessels while, at the same time, increase
the load capacity. the results from lÄss can be extended
to other types of vessels or industries, such as the offshore industry, where low structural weight is beneficial.
SSPA’s task in LÄSS
ssPA’s main involvement in the lÄss project consists of
managing one of the four demonstration ship concepts,
2/2006
2/2006
Lightweight construction
increases transport efficiency
lightweight construction increases transport efficiency
where the benefits of replacing the conventional mild
steel superstructure with a lightweight superstructure
made of aluminium is being investigated. Wallenius’s
PCtC vessel (Pure Car truck Carrier) M/s undine,
22 616 DWt and with a capacity of 5890 cars, is being
used as the concept ship. the area where the change of
material is being investigated is restricted to the ship’s
superstructure, and the aim is to transform the reduced
weight to a larger cargo hold without changing the vessel’s overall displacement or raising its centre of gravity.
the building material chosen is the aluminium alloy
eN-AW-6082-t6, which was selected mainly because of
the alloy’s high tensile strength and capability to be used
in extruded profiles. to fully utilise the material’s properties in a lightweight structure, the different parts should
be joined using a technique that either does not produce
a hAZ (heat Affected Zone) or that produces a very
small one. Friction stir Welding (FsW) produces a very
small hAZ and will therefore be used in the project.
extruded profiles are joined by FsW into large panels,
thus greatly reducing the amount of Mig-welding that is
needed.
Aluminium and the SOLAS code
When changing building material from steel to aluminium
the fire safety must be specifically considered because
aluminium loses strength rather rapidly with an increase
in temperature. to make the structure comply with the
sOlAs code and ensure the safety of the crew the
aluminium structure must be fitted with additional fire
insulation. the lÄss project consortium also includes
insulation companies that are participating by undertaking
large scale fire tests for both aluminium and composite
decks and bulkheads. these tests are being performed
to make certified solutions for lightweight fire insulation
available to the shipbuilding industry.
For the concept ship, a 9.6 m long section that represents the whole superstructure was defined and analyzed.
A number of different versions were then compared
primarily with regards to:
p
eter Gylfe, Project
Manager at SSPA. He received
his M.Sc. degree in Naval
Architecture at the Royal
Institute of Technology in
Stockholm, 1993. He has since
then been working within different areas of ship design
and was in 2003 employed by
SSPA. He is primarily working
with ship structure, weight and
stability, and project management and has been involved
in several projects for the
Swedish Defence Materiel
Administration.
Telephone: +46-31 772 9191
t
he illustration shows
the original superstructure, left,
the section of the superstructure
under consideration, centre, and
the extended superstructure, right.
r
ven hough he e ha been an
e o du ng ecen yea o ha mon e
he exchange o n o ma on be ween
h p and ho e he e a e
ue ha
need o be add e ed n o de o make
h pp ng mo e compe ve SSPA ha
oge he w h pa ne n he Ma N S
p o ec ocu ed on he mp ca on
and mp ovemenUtilising
o hepre-swirl
n o maflow
on
– reducing
costs
ow bo h comme
c a n fuel
o ma
on and
o c a documen a on a oc a ed w h
a h p ca
The Ma N S udy ha been no
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on and
h Eu opean Comm
hey have pa d a en on o he ac ha
ma me an po a o ace comp ex
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an po be ween EU po w h s he
con equence ha n a EU ma me
an po
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m n a ve comp ance ha make
e a ac ve Pe e G undev k a SSPA
wa nv ed o become nvo ved a an
– structure strength
– structural deflection
– the structure’s natural frequencies
– structural weight, including fire insulation
– economic aspects
the weight and economic aspects were reviewed under
the assumption that the cost for finished aluminium
structure is $10/kg and for finished steel structure is
$2/kg. the first version of the aluminium superstructure
including additional fire insulation weighs approximately
50% of the original steel version.
Coming versions of the superstructure, still under
development, will be based on direct calculations and
then optimised using Finite element software (Fe software).
the weight of coming versions is expected to be
drastically reduced compared to the initial design, mainly
thanks to a more optimised structure and the availability
of lighter insulation.
the results from the first aluminium structure indicate that the added initial cost for aluminium requires a
minimum of 180 additional vehicles to generate enough
profit to make the investments economically competitive.
this is based on a comparison with the steel superstructure and the assumption that added initial costs will have
a payback time of five years. the interesting question
is then how much steel structure on a PCtC can be
replaced with aluminium, and what revenue is expected?
New versions of the structures to be developed within
the lÄss project might give us the answer.
peter Gylfe
robert hjulbäck
Concept section weight
Weight
[kg]
n insulation weight
n structure weight
45 000
40 000
35 000
30 000
25 000
20 000
15 000
10 000
5 000
0
Steel
Alu-1
Sectionversion
ans Liljenberg,
Project Manager at SSPA.
He graduated (M. Sc.)
from Chalmers University
of Technology in 1968 and
was then for a few years
employed at the shipyard
Öresundsvarvet. In 1971 he
joined SSPA and has since then
been working mainly with hull
form optimisation of merchant
ships as well as high-speed
mono- and multi-hulls.
Telephone: +46-31 772 9031
Concept section cost
n insulation cost
n structure cost
JSD [$]
200 000
180 000
160 000
140 000
120 000
100 000
80 000
60 000
40 000
20 000
0
Steel
Alu-1
Sectionversion
he diagrams point out the differences in weight
and cost for the considered section.
Modern VLCCs
tress distributions from global Finite Element Analysis
(FEA), here showing hogging, are used to create boundary conditions
for the refined FEA of the considered section, in this case frequency
analysis.
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since the 80s, Daewoo shipbuilding & engineering Co.
ltd. (DsMe) of Korea has been a regular client with
ssPA. several generations of VlCC vessels have been
designed and optimised. today a large number of these
ships have been contracted and delivered to many owners. the designs have proved successful. is there anything
more to do?
F
our-bladed pre-swirl
stator on a VLCC model
highligt 2_2006_skarp7.indd 3
be g
The pre-swirl concept
06-11-18 22.26.03
öd
firmed the claimed improvements, in others they have
not. in our experience, the pre-swirl stator has been both
successful and unsuccessful, depending on the application.
s
obert Hjulbäck,
M.Sc. Naval Architect at SSPA.
He graduated from the Royal
Institute of Technology in
Stockholm in 2005 and has
since been employed by SSPA.
He has been working with
interpretation of classification
rules, structural design and
FEA for ships.
Telephone: +46 -31 772 9194
For an ordinary single screw vessel there are certain
propulsion losses that are not normally dealt with. the
most obvious is the substantial rotation energy lost in
the propeller slipstream. Means to recover that energy,
such as the grim wheel and contra rotating propellers,
have mostly been considered too expensive, technically
complicated or fragile. energy recovering fins aft of the
propeller are simple and robust but must be carried by
the rudder or the rudder horn in an accelerated flow,
and must not disturb the rudder efficiency. Devices ahead
of the propeller (ducts, fins, guide vanes) are easier to
integrate with the hull structure.
ssPA has model tested the devices listed above on
several occasions, as well as others such as pre-swirl
stator configurations. in some cases the tests have con-
HOTO Gunna
ome back sheet cavitation appeared downstream of
the hull CL and two of the stator blades. Ballast service loading condition. Both cavitation pattern and pressure pulses were improved
relative to the original design propeller without stator.
t
susanne abrahamsson
Everybody in the shipping business is aware of
escalating fuel oil prices, which are now significantly
higher than the rather low levels of the 90s.
Hydrodynamic improvement of ship propulsion has
become increasingly important as a result.
In the 70s and 80s the high fuel cost first resulted in
speed reduction, then in more careful ship operation
(e.g. opti-trim), and eventually in improved hydrodynamics in new hull designs. At the same time there was
increased interest in several energy saving devices.
echno ogy and capab e o an po ng
nc ea ng numbe o pede an and
cyc
n ne w h he c y
ong and
we exp e ed env onmen a po c e
and o e on po on env onmen a
a pec have a h gh p o y and a e
nked o capac y demand B oga and
ue ce a e a e na ve o be ana y ed
due o oo p n co and echno ogy
06-11-18 22.26.08
DsMe has been developing the pre-swirl stator concept
for a long time. the concept consists of stator blades
mounted on the boss end of the hull in front of the
propeller. these blades re-direct the flow before it enters
the propeller disc. the stator does not on its own save
energy or create a forward force; in fact it adds to resistance. it is the altered interaction with the propeller blade
that improves propulsive efficiency and results in power
reduction.
06-11-18 22.26.21
11
3/2007
My Sincere
Season’s
Greetings
to all of SSPA’s clients,
partners and colleagues in
the maritime community.
Thank you all for the
confidence shown in us
as we worked together
during 2007. Globalisation
continues to make the
wheels spin even faster,
creating growth and prosperity, heavily supported
by the maritime industry.
Climate change and
wise utilisation of energy
resources has been on
everybody’s mind in 2007.
This is evidenced by the
fact that the Nobel Peace
Prize will be given to the
Intergovernmental Panel
on Climate Change and
Albert Arnold Gore Jr. for
their efforts to build up
and disseminate greater
knowledge about manmade climate change and
to lay the foundations for
the measures that are
needed to counteract
such change.
This is a challenge we
have taken on at SSPA,
utilising and optimising
existing knowledge, and
seeking new knowledge
and innovations that can
strengthen our clients’
business concepts.
A myth claims that
we in Sweden have polar
bears roaming our streets.
It’s not true but we still
do care about the polar
bears’ living conditions.
Reaching for sustainable growth will make us
all winners.
Susanne Abrahamsson
3/2007
Early hull optimisation lowers
greenhouse gas emissions
No priority is greater for a modern oil/gas shipping
company than the safe transport of its product. Huge
effort goes into preventing oil spills and avoiding injuries and accidents. Similarly, companies are making a
determined effort to lower their Greenhouse Gas
(GHG) emissions.
SSPA has conducted extensive hull optimisation studies of different ship types, including product carriers,
Panamax and Suezmax tankers, VLCCs and LNGCs.
Operational, port, and seaway requirements and restrictions were used as the basis for parameter selection, and
main hull dimensions and different hull concepts such as
twin skeg and single screw were of most interest in the
studies. A ship is a compromise of many requirements
and along with economic aspects and power efficiency,
redundancy is important, as it is a key factor for minimising risks. The twin skeg concept, with its two propellers
and two rudders, is a design with very good redundancy.
Optimisation for best hull type and
hull parameters
SSPA has an extensive hull database with over 6000
models tested, including over 300 twin skeg hull forms.
Single screw
Panamax tanker.
There is a strong connection between rising oil prices
and the market for energy saving devices. The last time
the focus on reduced fuel costs was as great as it is
now was during the 1970s oil crisis. It is, however, a delicate balance for the designer to create an energy saving
device with a loss that is smaller than the gain it creates.
By using this database of information, it is possible to
perform parametric hull optimisation at a very early
stage of the design process. A procedure for theoretical calculation of hull resistance and propulsive power in
a seaway as well as in calm water has been developed.
Influence of hull type and hull dimensions such as length,
beam, draught, block-coefficient and displacement can be
investigated.
Significantly lower propulsive power
Studies performed by SSPA show that the gain achieved
by choosing the optimal hull type and hull main dimensions that conform to stated operational restrictions can
be significant. The difference in propulsive power is typically up to several percent in a seaway, and in some cases
10 percent or more has been observed.
BP’s environmental commitment
BP Shipping is committed to making continuous progress
on reducing its emissions and is therefore involved
in several innovative projects to help achieve this. BP
Shipping Ltd. commissioned SSPA to carry out a study,
the BP Hydrodynamic Development Program 2006, on
propulsive power versus various hull parameters. The
Hydrodynamic Development Program is an essential part
of BP’s plan to minimise the environmental impact and to
reduce emissions from its shipping activity.
H
enrik Andreasson, project Manager at SSPA.
He received his M.Sc. degree
in Naval Architecture in 1999
from Chalmers University of
Technology and has been employed at SSPA since then. He
works mainly with hull form
optimisation of merchant ships
as well as high-speed monohulls and multi-hulls.
Telephone: +46 -31 772 9072
E-mail:
[email protected]
The BP Hydrodynamic Development
Program
Twin skeg
Panamax tanker.
S
tatistically the twin skeg concept applied to full bodied
ships reduces the propulsive power in relation to conventional single
screw ships. The study shows a typical power reduction of several
percent and a maximum reduction of about 10 percent, for the
main hull dimensions and range of hull parameter data included in
the investigation.
O
ptimisations with
SHIPFLOW were carried
out by SSPA. Computation of
the boundary layer growth for a
single screw Panamax aftbody is
shown graphically here.
The study program comprises both single screw and twin
skeg hull designs. In this article one study - the Panamax
dimension study – is described in more detail. The power
demand for a single screw versus a twin skeg vessel is
highly dependent on ship size and restrictions in ship
draught. The aim of the project was to include environmental and operational considerations when choosing
hull type and hull main dimensions with respect to minimum power.
Over the last few decades shipyards have offered special
energy saving devices which were claimed to increase
ship propulsive performance. Examples of these devices
are fins mounted ahead of or behind the propeller, duct
surrounding the propeller or placed ahead of it, propeller blades with winglets and high tip load, asymmetrical
sterns, contra rotating propellers and so on. Many of
these devices have a sound physical basis and they have,
without doubt, meant reduced fuel consumption. Other
devices have, on the other hand, been examples of the
prevailing opinion that almost any measure can improve
the propulsive performance if the original design was
poor enough.
Propulsion principles
A hull towed through water will leave behind a wake of
disturbed water. This is what remains of the boundary
layer developed along the hull surface. It contains flow
accelerated in all three directions, and is to be considered
as a sum of the frictional part of the resistance and is
thereby a loss. The greater the wake, the greater the frictional part of the resistance. A propeller working within
the wake will recover some of the lost energy as it accelerates the axial component of the wake in the opposite
direction. In an ideal case where the propeller is working within the complete wake an optimum would be
achieved when the wake behind the propeller is equal to
the undisturbed water. For a real ship it is not possible to
have a propeller working within the complete wake. Any
devices that can concentrate the wake at the propeller
without increasing the resistance too much would therefore decrease the power required to propel the ship.
A rotating propeller will leave a swirling flow behind
it. Some of that energy is recovered by the rudder but
most of it is lost. Any device that can reduce the swirling
flow after the propeller without increasing the resistance
too much would also decrease the required power to
propel the ship. One example of such a device is the
DSME – Pre-swirl stator which was presented in SSPA
Highlights 2/2006. Many other energy saving devices, such
as contra rotating propellers, post-swirl stators, asymmetric sterns, and rudder bulbs work according to the
principle of reducing rotational losses in the propeller slip
stream.
Wake quality
The most critical factor for a successful propeller design
is the wake quality, and any effort spent on improving
wake quality in the early stages of a project is usually well
rewarded in the end.
A propeller blade working behind a ship will, during
its revolution, meet the flow at different angles of attack
because the wake flow field will vary in velocity and
direction with blade position. Variations in angle of attack
that are too large will not only cause poor efficiency, but
also increase the risk for vibration, noise, erosive cavitation, etc. An optimum propeller would therefore need to
constantly adjust its angle of attack during its revolution
and this adjustment would be different at different radii.
Panamax dimension study – minimum
propulsive power
Hull resistance and propulsive power were calculated for
operation in a seaway as well as in calm water. The main
hull dimensions – length, beam, draught, block-coefficient
and displacement – were varied over a wide range for
each concept, while the payload was kept constant.
SSPA’s accumulated database of statistics of single screw
and twin skeg hull form was utilised. The influence of sea
condition and operating environment in choosing hull
and propeller main dimensions with respect to minimum
power was then studied.
2
T
he purpose of
bilge vortex generator fins is
to stimulate the formation of
additional bilge vortices, which
equalise the wake. The fins are
fitted to the surface of the hull
upstream of the propeller.
Alien invasion is associated
with science fiction, but
today it is reality. We find
new clams in the waters of
the Swedish west coast. We
do not yet know if this is
bad or good, but we know
that the change is extremely
fast compared with natural
evolution. The natural
obstacles for the long distance journey of the clams
are surpassed by new technology. Fast changes are
hard to appreciate and
handle, and we get frightened.
Information is also travelling around the world
faster than we can handle.
An Old Russian Nobel Prize
winner was asked: ‘What is
the most important change
in your lifetime?’ He took a
few seconds to think about
this, and concluded: ‘I think
it is the information pollution.’ This was judged to be
more significant than two
world wars, invention of the
automobile, airplane, nuclear
power, transistor, and much
more. When the market
reacts to new statistics from
the US, followed by a counter reaction next day, the
financial consequences are
very significant.
WTO is having problems
developing a world without
trade obstacles. A Swedish
referendum has just voted
No to joining the European
common currency. Swedes
in general are very proglobalisation, but we have so
many views on what is the
right concept.
The world is becoming
ever smaller. Products and
ideas find their way fast and
irrevocably to new markets.
We can be pushed into a
new situation or we can
choose, develop and control
the process. Life is something in between!
13.59
07-11-15 08.29.55
It takes two skegs to increase
cargo capacity
Living organisms are being transported around the
globe in ships’ ballast water. Some of these alien species
have successfully established themselves in new locations, often to the detriment of the existing aquatic
ecosystems. Ballast water management to prevent the
spread of alien species has been receiving a lot of attention recently, both from regulatory agencies such as the
International Maritime Organization and from research
and development groups. SSPA is a partner in MARTOB, a three-year European Commission project that
is addressing the issue of ballast water management.
Within the next four years more than 100 LNG carriers will be delivered. Among these, the three largest
Korean shipyards will deliver 10 LNG carriers with a
cargo capacity of over 200,000 cbm.They will be the
largest LNG carriers so far, but even larger LNG carriers are being developed. At SSPA we are very proud to
have been involved in the development and model testing of these new giants.
some examples of alien species introductions include the
zebra mussel, the Chinese mitten crab, and the American
comb jelly. these introductions have had substantial
economic and environmental consequences. it has been
estimated that a new species is introduced to a region
somewhere in the world once every nine weeks. Although there are a number of ways new species are
introduced, ballast water is considered to be one of the
main vectors. once alien species are introduced, it is
extremely difficult and in some cases impossible to remove them. Prevention, therefore, is the best approach
to this problem.
Design is much more
than meets the eye
P
reparing the nutrient solution for on board testing of
the biological de-oxygenation method.
The regulatory response: fighting back
the international Maritime organization (iMo) has published voluntary guidelines for the control and management of ships’ ballast water. in addition, a number of
countries and regions have implemented mandatory
regulations. Ballast water exchange, the management
method that is currently practised, is described in iMo
guidelines. the guidelines are considered an interim
measure and iMo’s Marine Environmental Protection
Committee (MEPC) has been working to prepare a
ballast water convention that would eventually become
Z
ooplankton that have passed through a laboratory-scale
ballast water treatment system are examined under a microscope.
mandatory. the MEPC prepared a draft convention in july
2003 and this will be dicussed at a diplomatic convention
inFebruary2004.Thedraftconventionsetsoutstandards
for ballast water exchange, management, and treatment.
Ballast water exchange not completely
effective
T
he zebra mussel was introduced into the Great Lakes
and fouls water intakes and underwater structures, while the comb
jelly caused the decline of the Black Sea anchovy fishery. Both of
these species were introduced by ships’ ballast water.
Lars Afzelius
Ballast water exchange is the only ballast water management method that is widely used today. the method is
not, however, considered to be completely effective at
removing organisms from the ballast water. organisms
may remain in sediments in ballast water tanks during the
exchange procedure, and it is often not possible to completely flush out the water that was taken on at port.
Many new techniques are being investigated and tested as
a more effective method of managing ballast water. A
goal of the MArtoB project is to develop recommendations for alternative ballast water management methods
that involve treating the water on-board the ship.
since 2005, ssPA has been a part of the lÄss project,
lightweight Construction Applications at sea (www.
lass.nu), where the overall objective is to improve the
efficiency of marine transport. Development of four demonstration ship concepts, based on different ship types
and materials, is intended to point out the potential for
weight reduction, transport efficiency and environmental
performance.
Commercial factor talks
Advances in ship design and building are driven by
numerous factors of which the commercial factors are
the most influential. ship owners involved in the lÄss
project are able to reduce the weight and increase the
stability of their vessels while, at the same time, increase
the load capacity. the results from lÄss can be extended
to other types of vessels or industries, such as the offshore industry, where low structural weight is beneficial.
SSPA’s task in LÄSS
ssPA’s main involvement in the lÄss project consists of
managing one of the four demonstration ship concepts,
where the benefits of replacing the conventional mild
steel superstructure with a lightweight superstructure
made of aluminium is being investigated. Wallenius’s
PCtC vessel (Pure Car truck Carrier) M/s undine,
22 616 DWt and with a capacity of 5890 cars, is being
used as the concept ship. the area where the change of
material is being investigated is restricted to the ship’s
superstructure, and the aim is to transform the reduced
weight to a larger cargo hold without changing the vessel’s overall displacement or raising its centre of gravity.
the building material chosen is the aluminium alloy
eN-AW-6082-t6, which was selected mainly because of
the alloy’s high tensile strength and capability to be used
in extruded profiles. to fully utilise the material’s properties in a lightweight structure, the different parts should
be joined using a technique that either does not produce
a hAZ (heat Affected Zone) or that produces a very
small one. Friction stir Welding (FsW) produces a very
small hAZ and will therefore be used in the project.
extruded profiles are joined by FsW into large panels,
thus greatly reducing the amount of Mig-welding that is
needed.
Aluminium and the SOLAS code
When changing building material from steel to aluminium
the fire safety must be specifically considered because
aluminium loses strength rather rapidly with an increase
in temperature. to make the structure comply with the
sOlAs code and ensure the safety of the crew the
aluminium structure must be fitted with additional fire
insulation. the lÄss project consortium also includes
insulation companies that are participating by undertaking
large scale fire tests for both aluminium and composite
t
It directly affects the quality, performance, safety and
environmental elements. It
has a significant impact on
production, operation and
maintenance costs.
The design process is
equally important whether
it is a new control stabilizing system, ship type, or
port facility that is to be
realized. As designers and
engineers, SSPA’s mission is
to support our clients in
this area. We endeavour to
provide a creative environment where prevailing
know-how is allowed to be
questioned and challenged
for a short time in order to
seek novel ideas. It is our
sincere belief that it is at
the design stage where
you have the golden
opportunity to add value
to the specific product and
the total system it is operating in. The value added
will reward the owner,
operator, and other maritime shareholders throughout the life cycle of the
product.
But of course we
favour the process where
a high level of engineering
work is combined with creative elements and the
outcome is an efficient
and economic product that
is also attractive to the
eye.
Susanne Abrahamsson
Frictional effects from bio-fouling
and coatings
R
M
ichael leerandersen, project Manager
and ph.d. student at sspa. he
received his M.sc. in 1996
from the technical university of
denmark. he was employed at
sspa in 1997 as a researcher,
specialising in hull resistance
due to rough surfaces and
wash wave simulations using
CFd and measurements. he
has carried out several commercial and research projects
using CFd.
telephone: +46 - 31 772 9049
e-mail:
[email protected]
therefore “to decrease frictional resistance” the only
remaining viable option for an optimised hull shape
(except more specialised ships such as hover craft or
ses) is to modify the surface itself. A hydraulically smooth
surface is a surface which roughness is so small that no
further smoothing of the surface will benefit a frictional
decrease. but - almost no commercial or military ships,
even when newly built, have a hydraulically smooth
surface. the roughness of the steel plates and the roughness of the coating itself are too high, for which reason a
roughness allowance must be added to predict the total
resistance. Fouling and damage to the coating will further
increase the roughness allowance with time. therefore, it
is important to know how large effect the roughness has
on frictional resistance. to be able to investigate this ssPA
has devised different methods, both experimental and
computational.
Evaluating methods
skin friction on surfaces typically encountered on hull
surfaces, can be evaluated using several methods. the
simplest method would be to use empirical relations
linking the surface geometry to the skin friction, using
one or several parameters, as for example equivalent
sand roughness. the drawback of this approach is that
poor accuracy can be the result, if the rough surface
does not have a surface geometrically similar to measurements which the empirical model is based upon. CFd
(Computational Fluid dynamics) computations are also a
e
xample of full scale computation of the frictional resistance on the dyne tanker for a barnacle surface (top) and hydraulically smooth surface (bottom). red contour is the highest frictional
coefficient decreasing towards blue.
Pipe Flow
For surfaces with a large increase in friction coefficient,
the pipe measurement device is sufficiently accurate. the
principle is simple. Water is forced through a pipe with a
known flow rate, coated or bio-fouled on the inside, and
the pressure drop due to the friction on the inside of the
pipe is used to obtain the friction coefficient.
t
he sspa Flat plate
flow measurement
device in the towing
tank. the plate is 1m
deep and 6m long,
and is as thin as
practical to keep the
wave resistance as
low as possible.
During the past three years SSPA has been entrusted to
perform model tests for many of the Korean shipbuilders
such as Daewoo Shipbuilding and Marine Engineering
(DSME), Hyundai Heavy Industries (HHI) and Samsung
Heavy Industries (SHI) in their development of the new
very large LNG carriers with a cargo capacity of more
than 200,000 cbm. Considerable work has also been
performed for and on behalf of the world’s major oil
companies. More than 10 different hull forms have been
tested in extensive model test programs.
Further, for a large number of LNG Carriers with
cargo capacity of 130,000 to 160,000 cbm, tests have
been conducted for several different clients world wide.
It has been a hectic but exciting and instructive time for
SSPA and it is not over yet as even larger LNG carriers
are being developed.
The benefit of twin skeg
LNG ships have traditionally been single screw ships driven by a steam turbine.The size of the steam turbine
plant is relatively large and the turbine is expensive both
to manufacture and to maintain.Therefore a twin steam
turbine design has not been an attractive solution. New
and improved techniques have resulted in more efficient
reliquefication plants to take care of the LNG boil off and
more efficient dual fuel engines.The expensive steam turbine is no longer the only choice for the LNG ship.
With increasing cargo capacity, the beam-to-draught
T
he graph shows a comparison of required power for
one optimised twin skeg and one optimised single screw aft body of
a 200,000 m LNG carrier tested for DSME.The results suggest
that the twin skeg concept requires about 9% less power than the
single screw concept.The figure is copied from the paper “Core
design issues of large LNG Carrier”, Kim H C et. al., 2005, presented by DSME.
jörn Forsman,
Project Manager, M. Sc. in
Mechanical Engineering, graduated from Chalmers University of Technology in 1979. In
1980 he joined SSPA where
he has worked with development of oil spill recovery
equipment, arctic offshore
engineering, model testing and
simulation of ship manoeuvring, and has been responsible
for leading and co-ordinating
commercial projects in the
area of marine environment.
He has also been programme
manager for a number of
advanced international and
regional training programmes
on Coastal and Marine Environment Pollution Prevention
and Maritime Safety Management.
Telephone: +46 - 31 7729059
T
his graph shows cargo capacity of currently ordered
LNG vessels to be delivered within the next few years.
SSPA was coordinator for an interdisciplinary research
project where wake wash components were analysed
and numerically modelled. The project participants (SSPA,
SMHI, WET, WRE) represented several different disciplines, which is an advantage in a project with such an
extensive purpose. The project was focused on two types
of vessels: large vessels and high-speed vessels, respectively. A typical example of a large vessel is a conventional
Ropax ferry with a length of about 200 metres and a
travel speed of about 20 knots. A typical example of a
high-speed vessel is a high-speed ferry with a length of
about 100 metres and a travel speed of about 40 knots.
Other vessels, similar to the ferries described, were also
studied by this project.
Which waves are important?
Three different wake wash components were analysed in
the project.
– The Bernoulli waves: the formation of the water surface around the vessel hull due to the pressure distribution in the water around it.
– The Kelvin waves: the pattern consisting of divergent
and transverse waves, and the corresponding pattern in
shallow water.
– The solitary wave: a single wave that is sometimes
generated and that travels ahead of the vessel.
It was concluded that Kelvin and Bernoulli waves are
important for safety and shoreline erosion in archipelagos,
while solitary waves probably are not.
Tested by SSPA
today (autumn 2003) the total world lnG ship fleet
consists of 199 vessels, of which 29% are on order. furthermore,thereareoptionsforanother24vessels.
H
W
ake wash generated by high-speed vessels in deep
water may cause problems when reaching shallow nearshore waters.
Bernoulli wave
That the Bernoulli wave can cause a large lowering of the
water level along the banks when the vessel is operating
in a canal, a so-called drawdown, is a well-known phenomenon. In the present project, it was found that the
Bernoulli wave can also cause a significant drawdown in
bays and other seemingly sheltered areas along the fairway, when a large vessel passes outside them. This drawdown can be a direct result of the vessel’s passage but it
might also be a result of the Bernoulli wave being scattered by e.g. an island outside the bay. It is also possible
for a seiche, i.e. a periodic variation of the water level, to
be generated in the bay. Shoreline effects of the drawdown vary depending on whether the shore has a mild or
a steep slope. Shoreline erosion on mildly sloping shores
will be negligible. On steep shores (banks), the temporarily lowered water level during drawdown causes outward
hydraulic pressure gradients that decrease the structural
stability of the bank resulting in erosion.
210
190
170
150
130
110
90
T
70
raffic with large vessels
in archipelagos can generate
wave interaction effects with
islands and irregular coast-line
topographies.
50
Oct -05
Feb -08
o m
B
LNG – Future market demands
provide future challenges
Natural gas is overtaking coal as the second largest
source of energy after oil and is contributing to the shift
to lower carbon fuel. There are expectations that the
world consumption of natural gas will double by 2020
and could even, in the not too distant future, become
the dominant source of energy. The world’s reserve of
gas is today the energy equivalent to that of oil, and gas
is still being discovered in large quantities.
230
May -05
07-02-07 22.37.46
2/2003
When a vessel is moving through water, it generates
wake wash, i.e. waves and other water motions. There
is a risk that the wake wash causes environmental and/
or safety problems. Special attention has been directed
towards the wake wash from high-speed ferries, since it
has caused accidents resulting in injured people or
damaged boats etc. The wake wash from high-speed
ferries is also suspected to cause additional shoreline
erosion. The wake wash generated by large displacement vessels, such as conventional ferries, also causes
environmental impacts.
B
The value of experience
The initial design stage is important for a successful
design. It is essential to start with as optimal parameters
as possible. By using information from a hull database it is
possible to perform parametric hull optimisation at a
very early stage of the design process.
SSPA’s findings from model tests of more than 40
per cent of the LNG carriers built since 1990 is stored in
the SSPA hull database, which in total is constituted of
more than 6000 tested models. One very extensive
parametric hull optimisation study performed by SSPA a
few years ago, on behalf of ConocoPhillips Company,
resulted in the conclusion that for the new larger LNG,
the optimum block coefficient is much higher than what
was at that time commonly believed.This finding was
later confirmed in several model tests of large size LNG
carriers at the SSPA towing tank facility.
The study also identified those combinations of hull
parameters for which a twin skeg design could be more
beneficial than a traditional single screw design.
Namnlöst-2 4
Jul -09
Deliverance date
asse Olofsson,
Project Manager. He has been
employed at SSPA since 1964
and has mainly been involved
in hull form development work
for tankers, bulkers, LNG, and
Ro-Ro vessels. Hasse Olofsson
is an expert in hull design and
ship trial predictions.
Telephone: +46-31 772 9033
L
ars T. Gustafsson,
received his Master of Science
in Naval Architecture at
Chalmers University of Technology in 1993. After graduation he participated in a oneyear job rotation program and
joined SSPA in 1994. His earlier work was mainly with model
tests and CFD calculations and
from Jan. 1999 he has been
Market Manager at SSPA Ship
Design. He has from 1996 to
2002 been a member of technical committees within the
22 and 23 ITTC.
Telephone: +46-31 772 9010
SSPA LNG record of over 40%
during recent years ssPA has developed and model
tested a large percentage of the lnG tankers being built
in the world. out of the 128 lnG vessels contracted
after 1990 ssPA has, in co-operation with shipbilders,
developedandtested42%.Ifoptionsareincludedthe
number increases to 51%. Currently ssPA is investigating
several new lnG projects.
Examples are many Korean lnG ships for dsME,
hyundai, samsung and samho (halla) for ship owners
such as sK shipping, KlC, Bergesen, Exmar, BP shipping,
tapias, shell (on behalf of Bonny Gas transport) and A.P.
Möller. ssPA has also developed and tested the first
Chinese lnG tankers to be built at hudong shipyard in
shanghai. these vessels were designed by Chantiers de
l’Atlantique. Model tests have also been performed for
the iZAr lnG tankers of which the first is the inigo
tapias. the projects include ships with both membrane
type (Gtt) and Moss rosenberg spherical tanks.
ssPA has investigated lnG vessels in all testing facilities comprising towing tank, cavitation tunnel, and manoeuvring and seakeeping laboratory. during recent years
ssPA has also performed feasibility studies for new vessel
concepts, harbour manoeuvring simulations and lnG
terminal risk analyses.
Sizes start to increase
the year 1990 seems to mark the turning point when the
majority of lnG vessels ordered rose over 130,000 m .
DSME/Exmar, ‘Excalibur’
P
OD used as a contra-rotating propulsion unit (CRPu)
combined with a conventional propeller is a concept that SSPA has
investigated for ships with high power demand. The picture shows
model tests in the SSPA large cavitation tunnel, where the complete
towing tank model is mounted in front of the tested propulsion arrangement. The tests with an ABB CRP Azipod® unit were performed in 2003 on behalf of Daewoo Shipbuilding and Marine Engineering CO, LTD (DSME).
T
he hydrodynamic principles for POD used as a CRPu
are the same as for a thruster used as a CRPu, which were studied
at SSPA as early as 1984/1985. These investigations led to a patent, which later was sold to KAMEWA (Rolls Royce). The picture
shows the model of a 20 knot RoRo vessel. Tests were performed
as a part of a research program financed by the Swedish Board for
Technical Development (STU). Note that the thruster has many
similarities to the POD configuration above.
DSME/Bergesen, ‘Berge Boston’
SHI/BP Shipping, ‘British Trader’
4
highlights 3_2005_4
Very Large interest in
Crude Carriers
h
asse Olofsson, project Manager and one of sspA’s most experienced senior Consultants. he has been employed at sspA since 1964 and has primarily been working with hull form development for tankers, bulkers, lNG, and ro-ro vessels. hasse Olofsson is an expert in hull design and ship trial predictions.
telephone: +46 - 31 772 9033
e-mail: [email protected]
h
Revival of size
Since the seventies both displacement and beam have
continuously increased and today a majority of the VLCCs
ordered have a beam of 60 m. An interesting aspect of
this is that the size of today’s VLCCs is starting to approach the size of the smaller ULCCs of the seventies.
For example, the Kockums 350 000 dWT ULCC Series,
which was developed at SSPA, had a displacement close
to today’s VLCCs and a beam of 60 m. revival of size will
also mean a revival of technical problems and solutions
particular to these sizes.
Utilising pre-swirl flow
– reducing fuel costs
t
he 442500 dwt ulCC ti Africa was launched at daewoo in 2002 and built for hellespont. sspA had the hydrodynamic knowledge needed and was commissioned by daewoo to carry out the model tests of the hydrodynamic design. these first ulCCs to be built since the seventies are now owned by tankers international and ans Liljenberg,
Project Manager at SSPA.
He graduated (M. Sc.)
from Chalmers University
of Technology in 1968 and
was then for a few years
employed at the shipyard
Öresundsvarvet. In 1971 he
form optimisation of merchant
ships as well as high-speed
mono- and multi-hulls.
Telephone: +46-31 772 9031
MAX
M
m
m
A
m
T
s
firmed the claimed improvements, in others they have
not. in our experience, the pre-swirl stator has been both
successful and unsuccessful, depending on the application.
Modern VLCCs
h
T
since the 80s, Daewoo shipbuilding & engineering Co.
ltd. (DsMe) of Korea has been a regular client with
ssPA. several generations of VlCC vessels have been
designed and optimised. today a large number of these
ships have been contracted and delivered to many owners. the designs have proved successful. is there anything
more to do?
enrik Andreasson project Manager at sspA. he received his M. sc. degree in Naval Architecture 1999 at Chalmers university of technology and has since then been employed at sspA. he is primarily working with model tests and CFd calculations for hull form optimisations. telephone: +46 - 31 772 9072
he iran delvar is one of five in the first ever series of VlCCs built in China. the iran delvar was launched in 2003 at dalian New shipyard. hull form development in order to find the most optimised design was performed at sspA. these five VlCCs were he very beamy single-screw tanker silba was launched at uljanik shipyard in 1986. the hull form of this tanker, with an lpp/b of only 4.22, was optimised and tested at sspA. to assure good course-keeping characteristics special measures were taken, Flow analysis at model scale …
A CFD simulation not only predicts a total force and
moment, but also flow details in the whole computed
domain. For example, it tells engineers the pressure distribution anywhere on a blade, and identifies where the
flow is accelerating, decelerating, separating or cavitating.
Information on the magnitude and location of the minimum pressure assists a designer with judging the risk of
cavitation inception and location.These details cannot be
obtained with a conventional model test.
The geometry of the skewed propeller under study
was complicated by its high skewness, rake, and pitch
variation, which poses a great challenge for mesh genera-
he hexahedra
mesh at the boundary of the
computational domain, and the
surface mesh on the propeller
blade and shaft.
F
our-bladed pre-swirl
stator on a VLCC model
A
R
In the last decade POD propulsion applications have
increased significantly, mainly in the sectors of cruise
ships and ferries.Within the EU research project INTEGRATION the application of this type of propulsion
system for a fast Ropax ship has been investigated as an
alternative to a traditional twin screw solution.
INTEGRATION (Integration of sea land technologies for
an efficient intermodal door to door transport) is a project that aims to make short sea shipping in Europe more
attractive by developing new loading and unloading technologies for use onboard ships and in harbours. An additional aim of the project is to develop energy efficient
sea transport.
As part of the project, a Contra-Rotating Propulsion
unit (CRPu) was designed and tested at SSPA. A CRPu is
a propulsion system that combines a propeller on a shaft
with a POD propeller positioned behind the propeller.
The CRPu concept was selected because a high propulsive efficiency can be achieved when used in the right
application. Under the right design constraints the POD
can recover rotational energy left behind by the main
propeller.
SSPA has long experience of testing contra-rotating
propulsion arrangements. In the 1960s a systematic series
of contra-rotating propellers (CRP) on one shaft were
developed and tested. A CRPu system has the same
hydrodynamic principles as a contra-rotating propeller
with a thruster, which was studied and patented by SSPA
in the mid 1980s.
The increase in POD propulsion applications in
recent years may be justified by advantages such as good
manoeuvrability in harbours and flexibility for the general
arrangement of the ship. Of course installation of one
conventional propeller limits the freedom in the general
arrangement compared to a traditional POD installation.
tion. After much effort and practice, high quality hexahedra mesh can be generated within a short time now.
Grid dependency was studied in one condition with six
geometrically similar meshes. It was found that the local
quantities inspected showed a scattering with different
meshes, while the total K and K demonstrated a nonmonotonic convergence with mesh refinement.The prediction difference between the coarsest and the finest
mesh is less than 0.7% for K and less than 0.5% for K .
The grid dependency study significantly increased our
confidence in determining the size of the mesh that is
sufficient for a routine simulation of a propeller in open
water.
Experience with “Leading Edge” and other projects
shows that the CFD prediction of model scale K and K
in open water now agrees quite well with experiments,
normally with a difference from the measured data
around 2% for the K and 5% for the K . However, the
time to perform a full-range open water prediction is still
several times longer than an open water test in a towing
tank.
... to full scale
It is known that model testing suffers from scaling effects.
The prediction of full scale performance is essentially an
extrapolation based on model test results and semiempirical scaling laws. However, a CFD tool offers the
possibility to directly analyse the flow at full scale.The
results of full-scale computation demonstrated a clear
influence of viscous scaling effect on flows.The viscous
contribution to K and K was decreased at full scale as
expected. However, the pressure (or the lift) contribution
to K and K was found to have increased.The overall
07-02-07 23.10.48
P
The “Leading Edge” project addresses a growing problem
in today’s shipbuilding industry: the vibration caused by
tip vortex cavitation. It aims to develop tools to predict
and control tip and leading edge vortices in propeller
design. It has a strong consortium of 15 partners including propeller manufacturer, shipyards, model basins, universities, code developer, research institutes, and consultancy firms. State-of-the-art RANS codes were developed and validated against PIV measurements and model
test results with particular focus on the prediction of vortical flow detail at propeller tip and leading edge.Three
types of propellers were analysed in open water conditions at model and full scale.The project is now
approaching its end with many fruitful results.
DsMe has been developing the pre-swirl stator concept
for a long time. the concept consists of stator blades
mounted on the boss end of the hull in front of the
propeller. these blades re-direct the flow before it enters
the propeller disc. the stator does not on its own save
energy or create a forward force; in fact it adds to resistance. it is the altered interaction with the propeller blade
that improves propulsive efficiency and results in power
reduction.
t
2-2004.indd 4
elle Lundström,
Project Manager at SSPA. He
received his M.Sc. degree in
Naval Architecture at Chalmers
University of Technology in
2000, and worked one year
with car aerodynamics at Volvo
Car Corporation. In 2001 he
form and propulsion optimisation including CFD computations.
Telephone: +46-31 772 9056
E-mail:
[email protected]
More insight into propeller
performance with CFD
The pre-swirl concept
t
3/2005
Sida 10
A project on the leading edge
D
a-Qing Li,
Project Manager and
researcher. He received his
B.Sc. in Naval Architecture
from Huazhong University of
Science and Technology in
1986 and his Ph.D. in Ship
Hydrodynamics from Chalmers
University of Technology in
1994. He joined SSPA in 1998
and has since then been working with propeller/waterjet
propulsion, cavitation/erosion
and shallow water problems.
Telephone: +46-31 772 9053
ome back sheet cavitation appeared downstream of
the hull CL and two of the stator blades. Ballast service loading condition. Both cavitation pattern and pressure pulses were improved
relative to the original design propeller without stator.
testing of standard series of VLCCs for many of the Korean Shipyards such as daewoo Shipbuilding and Marine
engineering (dSMe) and Samsung Heavy Industries (SHI).
SSPA has experience from carrying out work for over
25 per cent of the VLCCs built in the world and, in addition to VLCCs, over 35 per cent of the ULCC fleet.
At the initial design phase SSPA offers speed – power
16.52
While traditional model testing remains a necessary
means of predicting propeller performance, use of CFD
(Computational Fluid Dynamics) software opens up
other possibilities in analysis and design of propellers.
Through the EU project “Leading Edge” SSPA has
gained more experience in meshing and simulating
flows around highly skewed propellers.The experience
has been used at SSPA in assisting with propeller
design.
For an ordinary single screw vessel there are certain
propulsion losses that are not normally dealt with. the
most obvious is the substantial rotation energy lost in
the propeller slipstream. Means to recover that energy,
such as the grim wheel and contra rotating propellers,
have mostly been considered too expensive, technically
complicated or fragile. energy recovering fins aft of the
propeller are simple and robust but must be carried by
the rudder or the rudder horn in an accelerated flow,
and must not disturb the rudder efficiency. Devices ahead
of the propeller (ducts, fins, guide vanes) are easier to
integrate with the hull structure.
ssPA has model tested the devices listed above on
several occasions, as well as others such as pre-swirl
stator configurations. in some cases the tests have con-
SSPA VLCC record
SSPA has been involved in the development and model
testing of a large percentage of the crude oil tanker fleet.
As early as the late 1960’s a standard series of VLCCs was
developed and tested at SSPA. The hull forms of the Kockums, Uddevalla and eriksberg tankers were all developed
at SSPA. other european shipyards that commissioned
SSPA are Chantiers de l’Atlantique and odense Staalskibsvaerft. SSPA has been involved in the development and
W
05-11-20
3/2005
Everybody in the shipping business is aware of
escalating fuel oil prices, which are now significantly
higher than the rather low levels of the 90s.
Hydrodynamic improvement of ship propulsion has
become increasingly important as a result.
In the 70s and 80s the high fuel cost first resulted in
speed reduction, then in more careful ship operation
(e.g. opti-trim), and eventually in improved hydrodynamics in new hull designs. At the same time there was
increased interest in several energy saving devices.
The new-building market for VLCC is still very strong
and shows no signs of declining. The first year of the new
millennium over 64 VLCCs were ordered from shipyards
the world over. This record could very well be beaten this
year.
w
possibility, but is a difficult venue as the roughness more
often than not must be considered irregular in shape.
Measurements are the final option. several methods
can be used, such as Pipe flow, Flat plate flow, Cavitation
tank or Couette cell measurements. the first 3 methods
have been designed, built and tested at ssPA in recent
years, each with their unique advantages and disadvantages. the Pipe flow device has been used for measuring
friction coefficients for a number of different bio-fouled
surfaces, more specifically barnacles of different sizes and
densities, whereas the plate has been utilized for surfaces
with smaller added frictional resistance, such as newly
applied coatings requiring a higher accuracy of measurement. Cavitation tank measurements will not be covered
further.
enrik andreasson
project Manager at sspa. he
received his M. sc. degree
in naval architecture 1999
at Chalmers university of
technology and has since then
been employed at sspa. he is
primarily working with model
tests and CFd calculations for
hull form optimisations.
telephone: +46 - 31 772 9072
sspa.se
06-11-18 22.26.03
6
The strong interest in the tanker segment shows no
signs of slackening. The new building prices for VLCCs
have risen almost to levels that were last seen around a
decade ago, when Golden Ocean Management hit problems. As one of the world’s most complete commercial
maritime test facilities with a reference list of over 25
per cent of all VLCC tankers built, SSPA has been commissioned for hull form development of several ongoing
VLCC projects all over the world.
w
ratio is increasing, since draught often is restricted.
Length-to-beam ratio remains unchanged, due to practical reasons for the cargo container system. Sloshing
restricts cargo container dimensional ratios.The combination of a relatively high Froude number and a high block
coefficient does not reduce the problem for larger ships.
Though the Froude number is slightly lowered due to
increased length, the block coefficient is increased. A service speed of 19.5 knots is still the standard though higher speeds have been considered.
2
2/2006
o
h
he illustration shows
the original superstructure, left,
the section of the superstructure
under consideration, centre, and
the extended superstructure, right.
1/2003
2
2/2004
m
Viscous resistance is the main resistance component
for most types of ships, ranging from about 50 percent
of the total resistance for high-speed craft to 90 percent for slow displacement ships such as tankers. The
significant part of the viscous resistance is the skin friction and to add to the misery, skin friction is difficult to
decrease by modifying hull shape as the most important
factors are wetted surface area and speed.
Sida 2
Stopping the alien invasion:
Ballast water treatment
Alien troublemakers on the high seas
International and national legislation will impose ever
more stringent requirements on marine transport. This,
together with the fact that fuel costs over a ship’s
lifetime have a decisive effect on its total life cycle
cost and its environmental impact, drives shipping
lines to constantly look for more efficient transport
systems. Lightweight construction of ships can thus
make a significant contribution to increasing the competitiveness of transport systems at sea.
05-09-29
highligt 3_2007_5.indd 4
Cargo capacity (1000 x m )
Globalisation
is here to stay!
07-11-15 08.29.52
MySincereSeason’s
Greetings
to all of ssPA’s clients, partners and colleagues in the
maritime society.
thank you all for the
confidence shown to us as
we worked together during 2006.
the near-term outlook
indicates that the global
economy will continue to
grow at a fast rate. this is
positive for the trade and
transport sectors, but stresses the need for efficient
resource utilisation.
in relative numbers the
shipping industry offers the
most energy efficient transport services but in absolute numbers the industry
is a major energy consumer.
however, in every complex
system, like shipping, there is
room for improvements. in
order to reduce energy consumption, different means are
available for the existing tonnage, ship conversions and
newbuildings.
technical innovations frequently enter the market,
like the ones described in
the articles “lightweight
construction increases transport efficiency” and “Utilising pre-swirl flow – reducing
fuel costs”. in the area of ship
management, development
work is being carried out in
areas such as advanced route
planning systems, and cargo
and ballast systems. the list
can be very long.
it is not only from an
economic perspective that
the efficient utilisation of
resources is beneficial. it is
also very significant from the
environmental perspective.
Preventive actions are today
regularly taken in order to
secure sustainable growth.
governments are introducing
and managing traffic control
systems in critical geographical areas, and the awareness
of environmental values is
spreading within the shipping
industry.
ssPA supports sustainable
growth.
1/2005
Lightweight construction
increases transport efficiency
susanne abrahamsson
4
highlights 2_2005
highligt 3_2007_5.indd 2
2/2006
The quest for lower fuel costs –
Save by improving wake quality
10
06-11-18 22.26.21
C
H
M
m
A o
o
H
o
o
However with today’s high oil prices in mind the CRPu is
a very interesting concept because of the possible
propulsive efficiency gain.
Designing a CRPu system
One of the prerequisites of the project was to use an
existing hull form. A hull form from a twin screw vessel
was selected and modified in the aft to incorporate the
main and POD propeller.The design speed for the CRPu
ship was set at 29 knots.The design speed is very high
and was a result of the proposed sailing route of the
ship.
The POD and main propellers were designed using
CONTRA, SSPA’s in-house software developed for lifting
line
P
er Lindell, Lic.Eng.,
Project Manager at SSPA. He
received his M.Sc. in Naval
Architecture at Chalmers
University of Technology and
was then employed at Kockums
Marine AB. He returned to
Chalmers for research work
and presented his Lic.Eng. thesis in 1992. He has been
employed at SSPA since 1993,
and works mainly with propulsion related projects.
Telephone: +46-31 772 9019
4
T
he env onmen a ub
ec have a way had a op ank
on SSPA agenda Above a e ec
on om he a e ve yea o
SSPA H gh gh
Please visit
our website
www.sspa.se
www
12
SSPA Highlights is published by
SSPA sweden AB.
P.O. Box 24001
Se-40022 Göteborg, Sweden
Phone Int. + 46 -31 772 90 00
Telefax + 46-31 772 91 24
E-MAIL postmaster @ sspa.se
WEB SITE www.sspa.se
Editor: Harriet Tegnér
Production: nils lindskoug
graphic design: Werner schmidt
Photo: sven wessling
Printed in Sweden
ISSN 1401-3711

the issue

Transcription

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