Computing surface sensitivity using discrete adjoints

[SumanVajjala]

Hi, I have a problem computing the surface sensitivities for drag (CD) using discrete adjoints in SU2.

The primal solution's density residual converged to E-12. The adjoint solution's residual (density) decreases to a level of -8 and starts increasing. Reducing the initial CFL number for the adjoint computations makes the convergence even worse.

I have used the same settings for computing primal and adjoint soutions.

SOLVER= RANS
KIND_TURB_MODEL= SA
SA_OPTIONS= NEGATIVE, EXPERIMENTAL
MATH_PROBLEM= DISCRETE_ADJOINT
RESTART_SOL= NO

REF_DIMENSIONALIZATION= FREESTREAM_PRESS_EQ_ONE

NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES
CFL_NUMBER= 4.0
MAX_DELTA_TIME= 1E10
CFL_ADAPT= YES
CFL_ADAPT_PARAM= ( 0.995, 1.005, 3.0, 8.0, 0.00001 )
ITER= 100000

LINEAR_SOLVER= FGMRES
LINEAR_SOLVER_PREC= ILU
LINEAR_SOLVER_ERROR= 1E-5
LINEAR_SOLVER_ITER= 20

CONV_NUM_METHOD_FLOW= JST
TIME_DISCRE_FLOW= EULER_IMPLICIT
OBJECTIVE_FUNCTION= DRAG

CONV_NUM_METHOD_ADJFLOW= JST
SLOPE_LIMITER_ADJFLOW= VENKATAKRISHNAN
ADJ_SHARP_LIMITER_COEFF= 3.0
ADJ_JST_SENSOR_COEFF= ( 0.0, 0.02 )
TIME_DISCRE_ADJFLOW= EULER_IMPLICIT
CFL_REDUCTION_ADJFLOW= 0.8
SENS_REMOVE_SHARP= YES
SENS_SMOOTHING= NONE
FROZEN_VISC_DISC= YES

CONV_NUM_METHOD_TURB= SCALAR_UPWIND
MUSCL_TURB= YES
SLOPE_LIMITER_TURB= NONE
TIME_DISCRE_TURB= EULER_IMPLICIT
CFL_REDUCTION_TURB= 1.0

I have tried with SU2 V8 and V8.2 without any success. Can anyone help me regarding these issues?

Suman

[SumanVajjala]

Update: When I let the adjoint solver converge to -8 then I get the following output for surface sensitivity. The visualization does not look right to me.