2d unsteady computations with deformation and adaptation for cosdyna tony gardner dlr as-hk
DESCRIPTION
2D unsteady computations with deformation and adaptation for COSDYNA Tony Gardner DLR AS-HK. Summary. Overview of project COSDYNA Computational geometry TAU deformation module Adaptation scheme Example computations and initial results Conclusion. Show Video 1 (Example of method). - PowerPoint PPT PresentationTRANSCRIPT
Folie 12D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
2D unsteady computations with deformation and adaptation for COSDYNA
Tony Gardner
DLR AS-HK
2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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Summary
Overview of project COSDYNA
Computational geometry
TAU deformation module
Adaptation scheme
Example computations and initial results
Conclusion
2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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Show Video 1 (Example of method)
2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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HighPerFlex
DLR internal High Performance Flexible Aircraft project (HighPerFlex) 2003-2006
LAWIA – (Last- und Widerstandsabminderung)
Load and drag reduction on a full A340 model by the steady CFD investigation of TED settings on an aeroelastically coupled aircraft.
COSDYNA – (Control surface dynamics)
Numerical and experimental investigation of unsteady profile and TED oscillations
JENIFA – (Jet engine interference in flutter analysis)
Experimental and numerical work to compliment the DLR-ONERA project WIONA (wing with oscillating nacelle)
2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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COSDYNA unsteady computations
To compute unsteady coefficients for comparison with TWG experiments in October 2006
TWG experiments will be performed with a 2D VC-Opt airfoil in the adaptive test section. Forced oscillations of flap and airfoil can be programmed or the airfoil can swing freely.
Computations must be at least partially performed beforehand due to time constraints.
Computations must include flap and airfoil movement.
Optimally, computations will not include gap flow
Computations include cases with strong shocks, and thus will optimally allow adaptation
2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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2D VC-Opt airfoil in TWG
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Geometry
VC-Opt, length 300mm
Design Mach =0.775
With 25% flap (gapless) deployed by grid deformation
Re=2 million
2D CENTAUR grid
Farfield at r=50 chords
(needs farfield vortex correction)
Surface points at 2mm spacing
28 structured sublayers (no cell chopping)
Built for y+=1
Raw grid has 50,000 points before 2D reduction
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Flap movement
Chimera
Requires a gap between body and flap (non-physical)
Gapless using automatic hole cutting is in development
Deformation
Can perform gapless movement
Requires definition of the new surface position
Handling the hinge requires care
Simplifies grid generation
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TAU Deformation
Tau deformation takes a surface deformation and deforms the volume grid to enclose this new surface
The grid points and numbering (GID) are preserved in the new grid, changing only the grid point positions. Solutions in TAU use GID.
A deformation can be expressed as (x, y, z), (x, y, z) or as a 3D, algebraic test deformation (z=C{y-y0}2)
TAU version 2005.1.1
Not explicitly 2D (accumulated machine precision errors)
Adaptation level information destroyed on reading of grid
No 2D algebraic test deformation
TAU version 2006.1.0
Grid quality problems with incremental deformations
No 2D algebraic test deformation
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TAU version
Based on 2005.1.1 with 2D adaptation patch
Added 2D deformation (Gerhold)
Added adaptation level loading (Gerhold)
Added 2D linear algebraic deformation
Deforming as: z=C(x-x0)
Using shell script in serial
Python was attempted, but I couldn’t get the scripts working.
Due to development status and lack of documentation?
Writing a solution each time step means that saved IO in Python is not as significant as it might be in other cases.
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Script execution in serial (Data passing as disk write)
Adaptation
Unsteady solver
Deformation
Unsteady solver
Steady solver
Deformation
Adaptation
Steady solver
Steady starting solution (20 mins)
Unsteady computation (2-3 days)
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Adaptation method
“Default rules” with the following additions:
Restrictions:
Maximum point number (150,000)
Minimum edge length (1mm)
Cut-out box to reduce cells in the wake
Adaptation type is “both”
Method:
Add cells to “maximum point number” in the steady calculation
Adapt after every time step
“Percentage of new points” is 20% to avoid a reduction in the number of points over time
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Example Grid 1/4
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Example Grid 2/4
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Example Grid 3/4
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Example Grid 4/4
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Time stepping study
Flap movement (): 0.0 1.0 degrees
Pitching amplitude (): 0.0 0.2 degrees
Reduced frequency (): 0.40 / 0.80
Ma: 0.80
Steps/period: 25, 50, 100, 200
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2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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Grid refinement study
Very difficult to undertake, even in 2D
Currently testing against a number of static, unrefined grids
Problems with large grid sizes of static grids
Refinement cases where surface grid size and tetrahedral stretching were reduced did not converge, up to 300000 cells.
Currently trying other refinement methods.
2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006
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Unsteady solver settings
100 inner iterations/timestep
200 timesteps/period
6 periods for a computation
SAE turbulence model
Central solver by Backward Euler
Multigrid scheme 5w
CFL number fine = 10
CFL number coarse = 20
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Show Videos 2 and 3
Ma=0.8
Re=2 million
=0.15 (~20 Hz)
Video2: Body oscillation only. = 0.0 0.2 degrees
Video3: Flap oscillation only. = 0.0 1.0 degrees
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First results
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Conclusions and further work
Under special conditions, 2D unsteady computations with adaptation and deformation appear to work.
Verification of the results with experiment still needs to be undertaken.
Grid refinement studies are still a problem
A similar approach could be undertaken using Python scripting.