[jjjjjf]

Hi everyone,

I'm currently implementing a 2D shape optimization of a hypersonic capsule at an angle of attack of 12º using SU2. The geometry of the capsule is aligned with the x-axis, and the freestream is rotated accordingly to introduce the AoA. I'm using a 2D FFD box defined with the following configuration:


MESH_FORMAT = SU2
MESH_FILENAME = malla_opt_2D_pt2.su2
MESH_OUT_FILENAME = malla_opt_2D_pt2_ffd.su2

MARKER_CUSTOM = ( wallupper, walllower, inlet, outlet )

DV_KIND = FFD_SETTING
DV_MARKER = ( wallupper, walllower )
DV_PARAM = ( MAIN_BOX, 24, 1, 0.0, 1.0 )

FFD_TOLERANCE = 1E-8
FFD_ITERATIONS = 500

FFD_DEFINITION = ( MAIN_BOX,
-0.1, -4, 0.0,
3.6, -4, 0.0,
3.6, 4, 0.0,
-0.1, 4, 0.0,
0.0, 0.0, 0.0,
0.0, 0.0, 0.0,
0.0, 0.0, 0.0
)

FFD_DEGREE = ( 24, 1, 0 )
FFD_CONTINUITY = 2ND_DERIVATIVE
% There is a symmetry plane (j=0) for all the FFD boxes
FFD_SYMMETRY_PLANE = YES


I defined the design variables over all control points in the i-direction (0 to 24) and j-direction (0 and 1), applied to both wallupper and walllower. The configuration looks like:


DEFINITION_DV = ( 19, 1.00 | wallupper, walllower | MAIN_BOX, i, j, 0.00, 1.00 );
(repeated for all i = 0...24 and j = 0,1)



Despite setting FFD_SYMMETRY_PLANE = YES, it seems like the symmetry condition is not being enforced during the optimization. Both wallupper and walllower are intended to be symmetric, but it is not working.


Has anyone encountered this issue before? Is there something wrong or missing in my setup that might cause the symmetry condition to be ignored?


Thanks in advance for your help!

[bigfootedrockmidget]

The FFD symmetry plane only works for 3D geometries.


For 2D, you can take out the degrees of freedom from the DEFINITION_DV list. You can remove the movement in the y-direction to keep the wall points on the same y-coordinate. If you also want to constrain the gradients at the wall, you could try with

% Surface grid continuity at the intersection with the faces of the FFD boxes.
% To keep a particular level of surface continuity, SU2 automatically freezes the right
% number of control point planes (NO_DERIVATIVE, 1ST_DERIVATIVE, 2ND_DERIVATIVE, USER_INPUT)
FFD_CONTINUITY= 2ND_DERIVATIVE

Or you can modify the movement of the FFD points yourself with a python script before calling SU2_DEF.