lfrem er How can we make the best from improved metocean

lfremer
www.ifremer.fr
How can we make the best from improved
metocean information ?
Michel OLAGNON
Ifremer, Brest
法国
Metocean Information
www.ifremer.fr
Metocean activities act as a support for design and
operation of offshore structures and for coastal
planning and management
Considering time scales ranging
from wave period (few seconds)
•
•
simulation of non linear wave fields
rogue wave characterization
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to climatology (some years)
•
•
sea-state process / climatology of the sea state chronology
merging of various data sources
they search for [parametric] models of the statistical
properties of sea conditions, further allowing to deal with
those parameters rather than with the whole huge
datasets of raw measurements or forecast models output.
www.ifremer.fr
What kind of applications are we studying
metocean conditions for ?
• OFFSHORE INDUSTRY (Oil production or Marine energy):
design and operation conditions for new concepts of
structures and/or new regions.
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• COASTAL MANAGEMENT: input to sediment transport,
water quality monitoring, emergency reaction, etc. studies.
• COMPUTER-AIDED SEARCH AND RESCUE: input to drift
models, decision in tow operations.
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www.ifremer.fr
The marine energy paradox:
The more energy at a marine location, the more interesting
it is to exploit it, and the more difficult it is to build a
structure that can withstand it and to work at sea to install
and maintain it.
…thus the need for very good knowledge of the sea
conditions.
lfremer
www.ifremer.fr
What sort of metocean environment
should we design against ?
• WAVES: we still do not master knowledge of low
frequency spectral contents, of non-linear characteristics,
of directionality, of multiple components, of unexpected
rogue waves.
• WINDS: our knowledge of North-Sea or GOM storms is
almost useless when faced with, for instance, sub-tropical
squalls; our measures of wind energy potential do not help
to predict extreme typhoons.
• CURRENTS: Though many scientists study them, they
have very different objectives and time-scales of interest
w.r.t. the offshore structures.
• LONG-TERM CLIMATE: missing, heterogeneous and
even conflicting data leave us too often in doubt.
lfremer
www.ifremer.fr
And what are the Metocean needs common to
oil production and to renewable energy ?
• Extreme loads and responses, leading to failure of the
structure.
• Fatigue and wear of the structure and of its components.
• Optimal operation, to reduce down-times and accident
risks.
• Special events readiness.
lfremer
www.ifremer.fr
The three plus one metocean pillars (and
challenges) of a successful future:
• Construction
of consistent reliable metocean
databases (from heterogeneous uncertain data
sources).
• Correct estimation of the risks of rare extreme
events encounters.
• Applying that long-term information also to shortterm decision in routine or emergency marine
operations.
• Making that information available in appropriate
forms to those who actually should use it.
Identifying the right parameters characterizing
sea conditions, to store into the database
lfremer
www.ifremer.fr
Multi-component spectra
On a practical wave energy case, 15-20%
underestimation of production when not using
component partitioning
Bringing harmony into the world of data
Merging of various data sources
lfremer
www.ifremer.fr
buoy - satellite - hindcast model
Extreme conditions
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Rogue wave characterization
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Abnormal waves or « just » rare waves
Happening when some special
conditions are met or just
randomly ?
Extreme conditions prediction
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www.ifremer.fr
Extrapolation problems
Models unreliable in extreme conditions
Lack of field and satellite data in typhoons
=> Need to add not so relevant data from neighbouring
areas
Extreme conditions prediction
lfremer
www.ifremer.fr
Extrapolation problems
Is the prediction for East China Sea lower because of
reality, or because severe typhoons were missed in
the database, or both ?
Extreme conditions prediction
lfremer
www.ifremer.fr
Some ideas now become feasible:
• Use a numerical model to « transfer » neighbouring
measurements to the location of interest
• Simulate a large set of typhoons by adding them
« artificially » into a numerical model of normal
meteorological conditions
• Use a much larger database by collecting all
available data from their owners
• …
Statistic Forecasting
lfremer
www.ifremer.fr
Sea-states
process
lfremer
www.ifremer.fr
A typical outcome of the progresses in metocean
knowledge could be a Sea State Simulator for
Tows and Marine Operations
Purpose :
Estimate with good accuracy the occurrence
probabilities of unfavourable scenarios for the
planned operation or for the continuation of the
current one.
www.ifremer.fr
Climate historical
database
Bootstrap replay
Past time-histories
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Typical Preparation of an
uncommon operation at sea
Simulations of the
operation
Decisions &
Choices
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Climate
statistics
RISK ANALYSIS
Design Case
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Evolution 1
Case study
Decisions
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Climate
Descriptions
Statistical models of
the time-history
process
SIMULATOR
Virtual but likely timehistories
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Evolution 2
(Many) simulations of
the operation
Decisions
Inputs:
www.ifremer.fr
Simple description of the operation and of the risks as a function of
sea conditions and of their time-history.
Climate description, for instance through a hindcast database.
Engine:
Modeling of the process of the sea states from a priori
knowledge and from the database.
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Simulation at will of as many time-histories as wanted.
Results:
Empirical distribution over the simulations of successes and
failures.
Analysis tools for the most common applications: fatigue over a
period, completion of an operation, …
www.ifremer.fr
Three plus
one metocean pillars
Making that information available in
appropriate forms to those who actually
should use it.
• Training
• Ease of access
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• Presentation in understandable formats
• Validation, confidence building, 24/7 availability,
no extra costs, ….
lfremer
www.ifremer.fr
Information must reach those who need it
lfremer
www.ifremer.fr
Information must reach those who need it
lfremer
www.ifremer.fr
Information must reach those who need it
lfremer
www.ifremer.fr
Information must reach those who need it
lfremer
www.ifremer.fr
Information must reach those who need it
10 years have passed, but have we done what we
should have so that it would not happen again ?
lfremer
www.ifremer.fr
The three plus one metocean pillars of a
successful future of work at sea:
• Construction of consistent reliable metocean databases (from
heterogeneous uncertain data sources).
• Correct estimation of the risks of rare extreme events encounters.
• Application of that long-term information also to short-term
decision in routine or emergency marine operations.
• Making that information available in appropriate forms to those
who actually should use it.
Let’s get together and build them together !
谢谢