1. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 1 2D unsteady computations with deformation and adaptation for COSDYNA Tony Gardner DLR AS-HK

2. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 2 Summary Overview of project COSDYNA Computational geometry TAU deformation module Adaptation scheme Example computations and initial results Conclusion

3. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 3 Show Video 1 (Example of method)

4. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 4 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)

5. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 5 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

6. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 6 2D VC-Opt airfoil in TWG

7. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 7 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

8. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 8 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

9. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 9 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-y 0 } 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

10. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 10 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-x 0 ) 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.

11. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 11 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)

12. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 12 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

13. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 13 Example Grid 1/4

14. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 14 Example Grid 2/4

15. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 15 Example Grid 3/4

16. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 16 Example Grid 4/4

17. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 17 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

18. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 18

19. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 19 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.

20. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 20

21. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 21

22. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 22 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

23. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 23 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

24. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 24 First results

25. 2D unsteady computations for COSDYNA > Tony Gardner > 21.06.2006 Folie 25 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.