Fall 2009 - CFD Beratung

Transcription

Volume 13 Issue 3 Fall 2009
Gridgen Gets Plane in the Air Fast
John B. Hinkey, Ph.D.
Geminus Technology Development, LLC
The test pilot refused to allow the micro air vehicle (MAV)
dispenser to drop from his airplane’s wing until someone
performed an aerodynamic assessment to determine if it might
be possible for the dispenser to return to hit his aircraft, perhaps
resulting in a very bad flight test day.
A key part of the aerodynamic assessment was a quick
computational fluid dynamic (CFD) analysis of the MAV dispenser
(a customized Vietnam-era MK-20 canister) with the fins
deployed to determine the basic aerodynamic characteristics.
So our customer came to us with a two week turn-around goal
of setting up a 180 degree symmetry simulation to estimate lift,
drag and stability properties versus angle of attack at various
deployment flight conditions (speed and altitude).
There was not enough time to work extensively with CAD to
produce a detailed geometry that had all the necessary geometry
construction aids to produce the grid, thus Gridgen’s internal
geometry/database generation tools became critical to producing
a quality grid in a very short time. An IGES file of the somewhat
simplified 3D geometry was all that was supplied and Gridgen
did the rest.
(Continues on page 2)
University Of Siegen Uses Gridgen
For Turbo Research
Julian Winkler, Institute Of Fluid And Thermodynamics
University Of Siegen, Germany
Figure 1: University of Siegen researchers use Gridgen’s
topological flexibility to create high quality grids on the
leading edge serrations. (Close view)
Figure 1: Far-field structured 180 degree symmetry block
grid topology
INSIDE THIS ISSUE
1
University of Siegen Uses Gridgen for Turbo Research
1
Partner Highlight
4
Training Dates
4
Product News
5
Toll Free 800-4PTWISE
The Turbomachinery Research Group at the University of Siegen
in Germany has been using Gridgen in several areas for several
years. They integrated Gridgen into the design cycle for one of
their primary areas of work, low-noise fan design. They also use
Gridgen for more detailed fluid dynamic research studies, where
Gridgen gives them a fine degree of control over grid spacing and
distribution needed for accurate simulations. In addition, Gridgen
is popular for student projects because it is easy to use.
Gridgen is fully integrated into the group’s low-noise fan design
cycle. First, an axial or radial fan is designed with an in-house
tool, then a multi-block structured grid is generated with Gridgen
(Continues on page 3)
www.pointwise.com
Pointwise® FocalPoint Fall 2009
2
(Continued from page 1)
The ease of generating the far- and near-field body grids allowed
us to concentrate on the more complicated tail fin grids, which
were composed of structured blocks intended to overlap the
main body grid by a minimum of two cells. The block structured
grids employed matching, non-matching and overlapped block
boundaries. The 3D mesh visualization and checking capability
was extensively used to ensure proper block connectivity and
block boundary overlap. To produce a high quality body cross
section, the database creation tools were used to generate a
slice along the body axis of the supplied 3D IGES file, which
produced a 2D body profile.
The main body blocks were then created as domains on the
axis of symmetry using this 2D body profile. After generating
an optimized 2D, multiple-domain mesh that extended away
to approximately 15 body lengths, these were extruded 180
degrees about the body axis. This provided an efficient method
to generate and, if necessary, modify and very quickly regenerate
the primary axisymmetric 180 degree extent body blocks.
Because of numerical robustness and accuracy issues, it was
desirable not to have a singular grid on the body axis at the
base surface.
Figure 2: Near-field structured 180 degree symmetry
block grid topology
For the non-axisymmetric base meshes, a 2D mesh (domain)
was produced via a central rectangular mesh and a surrounding
C-mesh. The interfaces between these meshes were optimized
by allowing the connectors common between these domains to
float during use of the elliptic solver to smooth the mesh. This
resulted in a very good mesh quality that became the 2D grid for
the base. The 2D base meshes were also used to construct the
downstream free stream boundary on the body axis by simply
copying and then scaling the base meshes appropriately, thus
saving time by not having to produce these meshes from scratch.
The blocks needing to extend from the base surface out to the
downstream free stream boundary were then constructed. Once
the main body blocks were completed, the blocks around one of
the fins were conventionally constructed using the fin surfaces
defined by the IGES file. The second set of fin blocks was easily
Figure 3: Overlapping structured blocks enclosing the
base fins
created by copying those from the first fin using the mirror tool.
Use of the mirror tool instead of simply copying via rotation
ensured that any geometry non-symmetries would be mirrored,
thus helping to ensure zero lift at zero angle of attack. The
ability to make rapid changes to the grid topology, grid density
and grid point distributions produced very few grid iterations,
which is a must when a fast turnaround is required. Due to the
fast simulation turn around requirements, wall functions were
planned to be used. Thus, the grids were clustered along the
body and fins to produce y+ values of approximately 50 using
hyperbolic tangent wall clustering. The outer flow boundaries of
the tail fin blocks were constructed by using subsets of the 180
degree axisymmetric body blocks, thus allowing for better block
overlapping. The grid diagnostic tools permitted rapid searches
for any poor quality grid regions. Gridgen’s native support for
the WindUS analysis code (from the NPARC Alliance) enabled
direct output files to the native .CGD file format for WindUS,
saving valuable time because no conversion utilities or other
grid generation/manipulation tools were required. The rapid
grid generation process helped to maximize the time available
for solving the flow field, resulting in more data being generated
at different flight speeds and altitudes. The high quality grid
produced a very high quality solution.
The flight test went off without a hitch and the ordinance
behaved as expected, producing the desired uneventful flight
test day.
Pointwise has worked closely with us to implement new
features in Gridgen/Pointwise and their technical support has
been superb, often turning around completely new Glyph
scripts or technical solutions within a day. Also, our company
has effectively implemented Gridgen with minimal training (the
available manuals are very good), saving time and resources to
put into other areas of our business. This has allowed us to have
rapid response to our customers’ needs and spend more time on
the simulation and analysis and less time with grid generation,
which is the whole point of having an effective grid generation
tool, isn’t it? n
3
University Of Siegen Uses Gridgen
For Turbo Research
(Continued from page 1)
and the flow through the fan is simulated with commercial
computational fluid dynamics (CFD) packages. An iterative
procedure is applied, based on the CFD results, to decide whether
a redesign with subsequent CFD analyses is necessary or, if the
simulation results are satisfactory, whether a prototype can be
manufactured and tested experimentally. This design process has
produced several successful low-noise fan designs.
The Turbomachinery Research Group also uses Gridgen in
conjunction with more advanced numerical techniques, such
as large-eddy simulation, to calculate the flow around airfoils
or in whole axial-flow fan assemblies. The main focus here is to
gain detailed insight into the flow physics and the calculation
of the acoustic source terms from the flow field for broadband
noise prediction.
One of the group’s recent studies focused on the influence of
small tripping devices attached to a single airfoil on boundarylayer development, transition from laminar to turbulent flow and
the acoustic implications in terms of trailing-edge noise of the
airfoil. For this purpose, the region close to the leading edge of
the airfoil, where forward facing serrations have been placed to
produce an artificial transition from laminar to turbulent flow in
the boundary layer, needed to be highly resolved.
Figure 1 shows a close-up view of this region of the grid. Grid
refinement around the boundary layer trips can be seen in this
figure. Also evident are the grid topology changes needed to
match the triangular shape of the trips with the rectangular
planform of the airfoil. Gridgen provides the researchers with
the degree of control necessary to create grids that resolve all
the relevant geometric and flow features, and so get accurate
numerical simulations.
Figure 3: The grid above was used for a CFD solution to provide
boundary conditions for the large-eddy simulation. The grid
below is a subset of that grid.
The effect of wind tunnel installations on aerodynamic loading
and acoustics is another very important factor to take into
account in a simulation like this. Wind tunnel interference
effects can cause experimental results to differ significantly
from freestream conditions. To incorporate these experimental
influences into the numerical simulation, a grid was developed
that included a simplified wind tunnel setup and the wind tunnel
nozzle, as shown above in Figure 3. Flow calculations on this
grid were performed to produce the correct inflow boundary
conditions for a large-eddy simulation on a truncated domain,
which was simply extracted from the full domain by deleting
unwanted blocks in the multi-block grid.
Gridgen has also been used for several student projects. Students
were very pleased with the software because of its simplicity.
Many challenges in using the software can be solved by intuition,
which makes Gridgen a valuable product for teaching, as well.
Gridgen has proven to be an efficient tool for high quality mesh
generation and will be used in the continuation of the present
projects and in classes taught at the University of Siegen. n
Figure 2: Leading edge serrations. (Far view)
Partner Highlight
EnSight CFD serves a variety of different sectors, including
academic and research, aerospace, automotive, biomedical
and chemical, construction, consultants, defense, electronics,
energy, manufacturing, marine, petrochemical and sports.
Image is courtesy of Drs. Yoram Yadlin and Arvin Shmilovich
of The Boeing Company.
Computational Engineering International (CEI) develops
cutting-edge visualization and animation software. With CEI’s
high-end software products, you can expand your simulation
process to new extremes.
CEI recently created a new interface based on its well-known
extreme visualization product, EnSight, specifically tailored
to the needs of CFD users. This new interface is simple
and focused, designed to allow you to explore your data
interactively. EnSight CFD will allow you to be more effective
in analyzing, visualizing and communicating simulation
results to your team.
“EnSight allows us to be very precise for the phenomena
we want to visualize,” said Alexis Lapouille of Aero Concept
Engineering (ACE). “If you have phenomena at X=1m on a
calculation, for example, FLUENT requires you to know where
the phenomena is to generate the plane for visualization.
With EnSight, you generate an X plane and then simply
move it until you find the phenomena. Similarly, the vortex
core feature allows you to find the vortex structure in very
little time.”
CEI has corporate headquarters in Apex, NC, and authorized
distributors around the globe. For more information, visit our
web site at www.EnSightCFD.com.
Darin McKinnis
VP Sales and Marketing
CEI, Inc.
Training Dates
Gridgen Advanced and Pointwise Standard Course
10-12 November 2009
Fort Worth, Texas
19-21 January 2010
Fort Worth, Texas
23-25 February 2010
East Coast
Gridgen Standard Course
23-25 March 2010
Fort Worth, Texas
11-13 May 2010
Fort Worth, Texas
15-17 June 2010
Midwest
13-15 July 2010
Fort Worth, Texas
Gridgen Standard Course
14-16 September 2010
Fort Worth, Texas
12-14 October 2010
West Coast
16-18 November 2010
Fort Worth, Texas
For more information, contact our Support Team at [email protected].
4
Product News
Dozens of Time Saving Tools
in Upcoming Pointwise Release
Gridgen Research Enhances
Overset Meshing
Pointwise’s upcoming release of Solid Meshing will provide a
suite of tools for addressing the issues associated with sloppy
CAD geometry and give you access to dozens of other new
meshing capabilities.
If you’ve ever wished Pointwise could export a file in your
favorite format, now’s your chance to turn that wish into
reality. Using the new CAE plug-in API, you can write your
own exporter for grid and boundary condition data so
that your solver appears in the CAE menu. Your ability to
customize Pointwise with advanced templates and macros
based on the Glyph scripting language has been enhanced
through the addition of support for Tk graphic interfaces
and the addition of procedural entity selection. Generating
turbomachinery grids is easier with the addition of rotational
and translational periodicity for curve and surface grids.
Two big changes on the hardware side of Pointwise give
you more options for using the software. 64-bit support
has been extended to the Microsoft Windows operating
system. 3D mice, specifically the SpaceNavigator™ and
SpaceExplorer™ devices from 3Dconnexion, now can be
used for image manipulation, in addition to Pointwise’s
traditional techniques. Exporting structured grids to CGNS,
addition of toolbar display commands, IGES export, a list of
your most recently used files, and many other tools await
you in the next release.
New features, added during an SBIR Phase I contract with the
U.S. Air Force Arnold Engineering Development Center, are
set to streamline overset meshing in Gridgen. One bottleneck
in the creation of composite grids is the removal of failed
interpolation points called orphans. Overset experts have
developed eclectic suites of tools to locate, visualize and
rectify problems in the composite grid. Although such toolsets
have proven effective, they are far from efficient because
the user must juggle many separate applications. Tools for
importing and visualizing overset assembly interpolation
data are being added to Gridgen. Orphan points will be
highlighted for easy identification. Furthermore, overset data
display will be pervasive throughout all Gridgen’s meshing
tools, providing an easy reference when modifying grids to
correct overset assembly problems. For complex problems,
Gridgen’s Examine feature will be bolstered with additional
overset assembly tools, making it possible to display overset
hole, fringe and orphan points on block topological and
physical cut planes. Furthermore, IBLANK, a key variable
in composite grid interpolation, will be visible as a scalar
function. Based on the success of this initial implementation
in Gridgen, future research would migrate these tools into
Pointwise and extend the coupling with overset assembly
software such as PEGASUS and SUGGAR. This work is
sponsored by Arnold Engineering Development Center, Air
Force Materiel Command and the USAF.
Automated gridding of complex geometries like this
centrifugal pump is made possible through the addition of
periodicity, scriptable selection and graphical script interfaces
to the latest Pointwise release.
Display of overset assembly orphan points in Gridgen.
213 South Jennings Avenue Fort Worth, Texas 76104-1107 Toll-free 800-4PTWISE
Tel (817) 377-2807 Fax (817) 377-2799 [email protected] www.pointwise.com
FocalPoint is a publication of Pointwise, Inc. It is for Gridgen and Pointwise users and people interested in learning more about numerical grid
generation. It includes information about the software, latest releases, future development plans, and tips on how to get the most out of Gridgen
and Pointwise while saving time in grid generation. Pointwise and Gridgen are registered trademarks and GridgenGlyph and PointwiseGlyph are
trademarks of Pointwise, Inc. All other trademarks are property of their respective owner. Copyright © 2009 Pointwise, Inc. All rights reserved.
5
First Class
US Postage
PAID
FT WORTH, TX
Permit 356
213 South Jennings Avenue
Fort Worth, Texas 76104-1107
RETURN SERVICE REQUESTED
Volume 13 Issue 3 Fall 2009
The Best Tips and Tricks
Let our technical support newsletter drive your productivity with the best tips and tricks from our experienced engineers. Sign up for
TheConnector at pointwise.com/theconnector and stay ahead of the game with our prerelease notes.
Just because there’s a new horse in the barn
doesn’t mean we’re sending Old Reliable
out to pasture.
As one of our customers said, “For real work, you use Gridgen.” That’s why it’s
known as the powerful CFD workhorse.
While we’re building up Pointwise, our next generation software, fans of
Gridgen don’t have to worry. Gridgen is not going away until our customers tell
us Pointwise can do everything Gridgen can.
In the meantime, our licenses let you run both products, so new users can jump
right in with Pointwise’s short learning curve and longtime Gridgen fans can
feel comfortable knowing it’s going to be there a long time.
You can feel conﬁdent about the future.
Reliable CFD Meshing is part of our name.
Sign up and be the ﬁrst to know: twitter.com/Pointwise

Fall 2009 - CFD Beratung

Transcription

Similar documents

Heritage Category: Listing List Entry No : 1227165 Grade: II County

HISTORICAL MAP PACK LEGEND

BerLin UrBAn Living- De ZwArTe HonD ArcHiTecTs

I+1

AB Reinforcement Grid

Grid Flexibility, a key priority for the Global Smart Grids Federation

WS-2CityG with grid connection

Art I - Distortion and Caricature