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Problem with the grid movement at high velocity |
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#1 |
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pierre desjardins
Join Date: Dec 2022
Posts: 1
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Hello, I have been trying to perform high-speed simulations using grid_movement for some time. However, after passing a certain speed (in my case 500 m/s), the calculation crashes when I try with a ramp or does not start with the following error:
Error in "void CSolver::SetResidual_RMS(const CGeometry*, const CConfig*)": ------------------------------------------------------------------------- SU2 has diverged (NaN detected). ------------------------------ Error Exit ------------------------------- Here is a simple example with a cylinder: % ------------- DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION ------------% % SOLVER= RANS %NAVIER_STOKES %EULER KIND_TURB_MODEL= SA %NONE MATH_PROBLEM= DIRECT REF_DIMENSIONALIZATION= DIMENSIONAL % ----------- COMPRESSIBLE AND INCOMPRESSIBLE FREE-STREAM DEFINITION ----------% % MACH_NUMBER= 0.0 AOA= 0.0 SIDESLIP_ANGLE= 0.0 INIT_OPTION= TD_CONDITIONS FREESTREAM_TEMPERATURE= 250.0 FREESTREAM_PRESSURE= 280.0 % ------------------------- TIME-DEPENDENT SIMULATION -------------------------------% RESTART_SOL= NO TIME_DOMAIN= YES TIME_MARCHING=DUAL_TIME_STEPPING-2ND_ORDER %DUAL_TIME_STEPPING-1ST_ORDER %DUAL_TIME_STEPPING-2ND_ORDER %DUAL_TIME_STEPPING-1ST_ORDER TIME_STEP= 0.001 MAX_TIME= 50.0 INNER_ITER= 10 RESTART_ITER= 0 TIME_ITER= 500 GRID_MOVEMENT= ROTATING_FRAME TRANSLATION_RATE = -633.941 0.0 0.0 MACH_MOTION= 2 %MARKER_SHROUD= (wall) %RAMP_ROTATING_FRAME= YES %RAMP_ROTATING_FRAME_COEFF= (-100.0, 1.0, 1000) % ---------------------- REFERENCE VALUE DEFINITION ---------------------------% % REF_ORIGIN_MOMENT_X = 0.00 REF_ORIGIN_MOMENT_Y = 0.00 REF_ORIGIN_MOMENT_Z = 0.00 REF_LENGTH= 10.0 REF_AREA= 20.0 % -------------------- BOUNDARY CONDITION DEFINITION --------------------------% % %MARKER_EULER= ( wall ) MARKER_ISOTHERMAL= (cylinder,250) MARKER_WALL_FUNCTIONS= ( cylinder, STANDARD_WALL_FUNCTION ) MARKER_FAR= ( farfield ) MARKER_PLOTTING= ( cylinder ) MARKER_MONITORING= ( cylinder ) % ------------- COMMON PARAMETERS DEFINING THE NUMERICAL METHOD ---------------% % NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES %GREEN_GAUSS CFL_NUMBER= 10 CFL_ADAPT= NO CFL_ADAPT_PARAM= ( 1.5, 0.5, 1.0, 100.0 ) RK_ALPHA_COEFF= ( 0.66667, 0.66667, 1.000000 ) LINEAR_SOLVER= FGMRES %BCGSTAB %FGMRES %LINEAR_SOLVER_SMOOTHER_RELAXATION= 10 LINEAR_SOLVER_PREC= LU_SGS %(ILU, LU_SGS, JACOBI) %LINEAR_SOLVER_ITER= 5 % ----------------------- SLOPE LIMITER DEFINITION ----------------------------% % %VENKAT_LIMITER_COEFF= 0.1 %REF_SHARP_EDGES= 3.0 %SENS_REMOVE_SHARP= NO % -------------------------- MULTIGRID PARAMETERS -----------------------------% % MGLEVEL= 0 MGCYCLE= V_CYCLE MG_PRE_SMOOTH= ( 1, 2, 3, 3 ) MG_POST_SMOOTH= ( 2, 2, 2, 2) MG_CORRECTION_SMOOTH= ( 0, 0, 0, 0 ) MG_DAMP_RESTRICTION= 0.8 MG_DAMP_PROLONGATION= 0.8 % -------------------- FLOW NUMERICAL METHOD DEFINITION -----------------------% % CONV_NUM_METHOD_FLOW= JST %ENTROPY_FIX_COEFF= 1.0 MUSCL_FLOW= NO SLOPE_LIMITER_FLOW= BARTH_JESPERSEN %BARTH_JESPERSEN JST_SENSOR_COEFF= ( 0.5, 0.02 ) TIME_DISCRE_FLOW= EULER_IMPLICIT % -------------------- TURBULENT NUMERICAL METHOD DEFINITION ------------------% % CONV_NUM_METHOD_TURB= SCALAR_UPWIND MUSCL_TURB= NO SLOPE_LIMITER_TURB= BARTH_JESPERSEN TIME_DISCRE_TURB= EULER_IMPLICIT % --------------------------- CONVERGENCE PARAMETERS --------------------------% % CONV_RESIDUAL_MINVAL= -15 CONV_STARTITER= 10 CONV_CAUCHY_ELEMS= 100 CONV_CAUCHY_EPS= 1E-6 % ------------------------- INPUT/OUTPUT INFORMATION --------------------------% % MESH_FILENAME= mesh_cylinder_lam.su2 %mesh MESH_FORMAT= SU2 MESH_OUT_FILENAME= mesh_out.su2 SOLUTION_FILENAME= restart_flow.dat READ_BINARY_RESTART= YES TABULAR_FORMAT= CSV CONV_FILENAME= history RESTART_FILENAME= restart_flow.dat VOLUME_FILENAME= flow SURFACE_FILENAME= surface_flow OUTPUT_WRT_FREQ= 5 SCREEN_OUTPUT= (ITER, RMS_RES, LIFT, DRAG) OUTPUT_FILES= (PARAVIEW) BREAKDOWN_FILENAME= forces_breakdown.dat WRT_FORCES_BREAKDOWN = YES mesh -> Tutorials/compressible_flow/Laminar_Cylinder /mesh_cylinder_lam.su2 I used the cylinder mesh provided in the SU2 tutorials for my example. However, the problem does not seem to be related to the mesh since I tried with a BL well-resolved mesh for the problematic speed. Thanks for your help! |
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#2 |
Senior Member
bigfoot
Join Date: Dec 2011
Location: Netherlands
Posts: 596
Rep Power: 17 ![]() |
The numerical stability of solvers often depends on the velocity, so it is not guaranteed that your setup works when you change the velocity.You could try to start a simulation with a lower velocity that converges and then restart from that solution.
How do you initialize the flow? A better initial condition might help in getting the solution started properly. You also have to check what the actual Reynolds number and the Mach number is and choose the appropriate solver. Probably RANS is OK, but just check to be sure. If Ma<0.3, you might be better off using the incompressible solver. |
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