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Solver instability with increasing Mach number |
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Marcel
Join Date: Jul 2023
Location: Netherlands
Posts: 3
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Dear,
I am trying to run a 2D viscous simulation of artillery projectiles. The objective is to compare results from CFD packages with experimental data. I created a mesh using gmsh (that I can share with you when desirable). For the cfg file I am reusing code that was used to simulate a supersonic wing, I was expecting it to perform well for this case aswell. However upon increasing the Mach number the solver seems to become less and less stable. I would greatly appreciate any help you could offer me on this problem (see the cfg below for more information) Kind regards, Marcel % ------------- DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION ------------% % % Physical governing equations (EULER, NAVIER_STOKES, % WAVE_EQUATION, HEAT_EQUATION, FEM_ELASTICITY, % POISSON_EQUATION) SOLVER= RANS % % Specify turbulent model (NONE, SA, SA_NEG, SST) KIND_TURB_MODEL= SST % % Mathematical problem (DIRECT, CONTINUOUS_ADJOINT) MATH_PROBLEM= DIRECT % % Restart solution (NO, YES) RESTART_SOL= NO % -------------------- COMPRESSIBLE FREE-STREAM DEFINITION --------------------% % % Mach number (non-dimensional, based on the free-stream values) MACH_NUMBER= 2.00 % % Angle of attack (degrees, only for compressible flows) AOA= 0.00 % % Free-stream temperature (288.15 K by default) FREESTREAM_TEMPERATURE= 288.15 % % Reynolds number (non-dimensional, based on the free-stream values) REYNOLDS_NUMBER= 1E7 % % Reynolds length (1 m by default) REYNOLDS_LENGTH= 0.009 % ---------------------- REFERENCE VALUE DEFINITION ---------------------------% % % Reference origin for moment computation REF_ORIGIN_MOMENT_X = 0.25 REF_ORIGIN_MOMENT_Y = 0.00 REF_ORIGIN_MOMENT_Z = 0.00 % % Reference length for pitching, rolling, and yawing non-dimensional moment REF_LENGTH= 0 % % Reference area for force coefficients (0 implies automatic calculation) REF_AREA= 0 % -------------------- BOUNDARY CONDITION DEFINITION --------------------------% % % Navier-Stokes wall boundary marker(s) (NONE = no marker) MARKER_HEATFLUX= ( shell, 0.0 ) % % Farfield boundary marker(s) (NONE = no marker) MARKER_FAR= ( outer ) % % Marker(s) of the surface to be plotted or designed MARKER_PLOTTING= ( shell ) % % Marker(s) of the surface where the functional (Cd, Cl, etc.) will be evaluated MARKER_MONITORING= ( shell ) % ------------- COMMON PARAMETERS DEFINING THE NUMERICAL METHOD ---------------% % % Numerical method for spatial gradients (GREEN_GAUSS, WEIGHTED_LEAST_SQUARES) NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES % % Courant-Friedrichs-Lewy condition of the finest grid CFL_NUMBER= 2.5 % % Adaptive CFL number (NO, YES) CFL_ADAPT= NO % % Parameters of the adaptive CFL number (factor down, factor up, CFL min value, % CFL max value ) CFL_ADAPT_PARAM= ( 1.5, 0.5, 1.0, 100.0 ) % % Number of total iterations ITER= 99999 % % Linear solver for the implicit formulation (BCGSTAB, FGMRES) LINEAR_SOLVER= BCGSTAB % % Min error of the linear solver for the implicit formulation LINEAR_SOLVER_ERROR= 1E-6 % % Max number of iterations of the linear solver for the implicit formulation LINEAR_SOLVER_ITER= 2 % -------------------------- MULTIGRID PARAMETERS -----------------------------% % % Multi-Grid Levels (0 = no multi-grid) MGLEVEL= 0 % % Multi-grid cycle (V_CYCLE, W_CYCLE, FULLMG_CYCLE) MGCYCLE= W_CYCLE % % Multi-grid pre-smoothing level MG_PRE_SMOOTH= ( 1, 2, 3, 3 ) % % Multi-grid post-smoothing level MG_POST_SMOOTH= ( 0, 0, 0, 0 ) % % Jacobi implicit smoothing of the correction MG_CORRECTION_SMOOTH= ( 0, 0, 0, 0 ) % % Damping factor for the residual restriction MG_DAMP_RESTRICTION= 0.95 % % Damping factor for the correction prolongation MG_DAMP_PROLONGATION= 0.95 % -------------------- FLOW NUMERICAL METHOD DEFINITION -----------------------% % % Convective numerical method (JST, LAX-FRIEDRICH, CUSP, ROE, AUSM, HLLC, % TURKEL_PREC, MSW) CONV_NUM_METHOD_FLOW= JST % % Monotonic Upwind Scheme for Conservation Laws (TVD) in the flow equations. % Required for 2nd order upwind schemes (NO, YES) MUSCL_FLOW= YES % % Slope limiter (VENKATAKRISHNAN, MINMOD) SLOPE_LIMITER_FLOW= VENKATAKRISHNAN % % Coefficient for the limiter (smooth regions) VENKAT_LIMITER_COEFF= 0.03 % % 2nd and 4th order artificial dissipation coefficients JST_SENSOR_COEFF= ( 0.5, 0.02 ) % % Time discretization (RUNGE-KUTTA_EXPLICIT, EULER_IMPLICIT, EULER_EXPLICIT) TIME_DISCRE_FLOW= EULER_IMPLICIT % -------------------- TURBULENT NUMERICAL METHOD DEFINITION ------------------% % % Convective numerical method (SCALAR_UPWIND) CONV_NUM_METHOD_TURB= SCALAR_UPWIND % % Monotonic Upwind Scheme for Conservation Laws (TVD) in the turbulence equations. % Required for 2nd order upwind schemes (NO, YES) MUSCL_TURB= NO % % Time discretization (EULER_IMPLICIT) TIME_DISCRE_TURB= EULER_IMPLICIT % ---------------- ADJOINT-FLOW NUMERICAL METHOD DEFINITION -------------------% % Adjoint problem boundary condition (DRAG, LIFT, SIDEFORCE, MOMENT_X, % MOMENT_Y, MOMENT_Z, EFFICIENCY, % EQUIVALENT_AREA, NEARFIELD_PRESSURE, % FORCE_X, FORCE_Y, FORCE_Z, THRUST, % TORQUE, FREE_SURFACE, TOTAL_HEAT, % MAXIMUM_HEATFLUX, INVERSE_DESIGN_PRESSURE, % INVERSE_DESIGN_HEATFLUX) OBJECTIVE_FUNCTION= DRAG % % Convective numerical method (JST, LAX-FRIEDRICH, ROE) CONV_NUM_METHOD_ADJFLOW= JST % % Monotonic Upwind Scheme for Conservation Laws (TVD) in the adjoint flow equations. % Required for 2nd order upwind schemes (NO, YES) MUSCL_ADJFLOW= YES % % Slope limiter (NONE, VENKATAKRISHNAN, BARTH_JESPERSEN, VAN_ALBADA_EDGE, % SHARP_EDGES, WALL_DISTANCE) SLOPE_LIMITER_ADJFLOW= NONE % % Coefficient for the sharp edges limiter ADJ_SHARP_LIMITER_COEFF= 3.0 % % 2nd, and 4th order artificial dissipation coefficients ADJ_JST_SENSOR_COEFF= ( 0.0, 0.01 ) % % Reduction factor of the CFL coefficient in the adjoint problem CFL_REDUCTION_ADJFLOW= 0.75 % % Time discretization (RUNGE-KUTTA_EXPLICIT, EULER_IMPLICIT) TIME_DISCRE_ADJFLOW= EULER_IMPLICIT % % Adjoint frozen viscosity (NO, YES) FROZEN_VISC_CONT= YES % --------------------------- CONVERGENCE PARAMETERS --------------------------% % % Min value of the residual (log10 of the residual) CONV_RESIDUAL_MINVAL= -8 % % Start convergence criteria at iteration number CONV_STARTITER= 10 % % Number of elements to apply the criteria CONV_CAUCHY_ELEMS= 100 % % Epsilon to control the series convergence CONV_CAUCHY_EPS= 1E-6 % % ------------------------- INPUT/OUTPUT INFORMATION --------------------------% % % Mesh input file MESH_FILENAME= ../Mesh2D.su2 % % Mesh input file format (SU2, CGNS, NETCDF_ASCII) MESH_FORMAT= SU2 % % Mesh output file MESH_OUT_FILENAME= mesh_out.su2 % % Restart flow input file SOLUTION_FILENAME= solution_flow.dat % % Restart adjoint input file SOLUTION_ADJ_FILENAME= solution_adj.dat % TABULAR_FORMAT= CSV % % Output file convergence history (w/o extension) CONV_FILENAME= history % % Output file restart flow RESTART_FILENAME= restart_flow.dat % % Output file restart adjoint RESTART_ADJ_FILENAME= restart_adj.dat % % Output file flow (w/o extension) variables VOLUME_FILENAME= flow_SST % % Output file adjoint (w/o extension) variables VOLUME_ADJ_FILENAME= adjoint % % Output objective function gradient (using continuous adjoint) GRAD_OBJFUNC_FILENAME= of_grad.dat % % Output file surface flow coefficient (w/o extension) SURFACE_FILENAME= surface_flow_SST % % Output file surface adjoint coefficient (w/o extension) SURFACE_ADJ_FILENAME= surface_adjoint % % Writing solution file frequency OUTPUT_WRT_FREQ= 250 % % % Screen output fields SCREEN_OUTPUT= (INNER_ITER, RMS_DENSITY, RMS_NU_TILDE, LIFT, DRAG, TOTAL_HEATFLUX) |
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su2, super sonic |
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