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Static FSI with Compressible Flow (SU2 7.1.1) 

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April 1, 2021, 15:31 
Static FSI with Compressible Flow (SU2 7.1.1)

#1 
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Sangeet
Join Date: Jun 2017
Location: India
Posts: 43
Rep Power: 7 
Hello,
I am currently running a static FSI case of supersonic flow over a compression ramp where the ramp is flexible (FEM grid with clampedclamped boundary condition). The fluid only case (rigid ramp) converges well but when i try to run the coupled simulation, the structure's convergence is very poor. I tried both large and small deformations in the structural config file and I also tried plane stress and plain strain conditions. None of these cases showed any improvement. The google drive link with config files and the grid files is https://drive.google.com/drive/folde...7L?usp=sharing I have also attached a picture of the grids for a quick idea. Please kindly suggest on what I could be possibly doing wrong. The fluid config file is Code:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % SU2 configuration file % % Case description: Supersonic flow over a wedge in a channel. % % Author: Thomas D. Economon % % Institution: Stanford University % % Date: 2012.10.07 % % File Version 5.0.0 "Raven" % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION % % % Physical governing equations (EULER, NAVIER_STOKES, % WAVE_EQUATION, HEAT_EQUATION, FEM_ELASTICITY, % POISSON_EQUATION) SOLVER= RANS % % If NavierStokes, kind of turbulent model (NONE, SA) KIND_TURB_MODEL= SST % % Mathematical problem (DIRECT, CONTINUOUS_ADJOINT) MATH_PROBLEM= DIRECT % % Restart solution (NO, YES) RESTART_SOL= NO %  COMPRESSIBLE AND INCOMPRESSIBLE FREESTREAM DEFINITION % % % Mach number (nondimensional, based on the freestream values) MACH_NUMBER= 2.9 % % Angle of attack (degrees) AOA= 0.0 % % Sideslip angle (degrees) SIDESLIP_ANGLE= 0.0 % % Freestream temperature (288.15 K by default) FREESTREAM_TEMPERATURE= 109.619686800895 % % Reynolds number (nondimensional, based on the freestream values) REYNOLDS_NUMBER= 148000 % % Reynolds length (in meters) REYNOLDS_LENGTH= 4.0454e03 %  REFERENCE VALUE DEFINITION % % % Reference origin for moment computation REF_ORIGIN_MOMENT_X = 0.0 REF_ORIGIN_MOMENT_Y = 0.00 REF_ORIGIN_MOMENT_Z = 0.00 % % Reference length for pitching, rolling, and yawing nondimensional moment REF_LENGTH= 1.0 % % Reference area for force coefficients (0 implies automatic calculation) REF_AREA= 1.0 %  BOUNDARY CONDITION DEFINITION % % % NavierStokes wall boundary marker(s) (NONE = no marker) MARKER_HEATFLUX= ( WALL1, 0.0, RAMP, 0.0, WALL2, 0.0 ) % % Supersonic inlet boundary marker(s) (NONE = no marker) % Total Conditions: (inlet marker, temperature, static pressure, velocity_x, % velocity_y, velocity_z, ... ), i.e. all variables specified. MARKER_SUPERSONIC_INLET= ( INLET, 109.619686800895, 13366.4283315982, 608.621433419003, 0.0, 0.0 ) % % Outlet boundary marker(s) (NONE = no marker) % Format: ( outlet marker, back pressure (static), ... ) MARKER_OUTLET= ( OUTLET, 10000, UPPER, 10000) MARKER_SYM= ( SYM_PLANE ) % % Marker(s) of the surface to be plotted or designed MARKER_PLOTTING= ( WALL1, RAMP, WALL2 ) % % Marker(s) of the surface where the functional (Cd, Cl, etc.) will be evaluated MARKER_MONITORING= ( WALL1, RAMP, WALL2 ) %  COMMON PARAMETERS DEFINING THE NUMERICAL METHOD % % % Numerical method for spatial gradients (GREEN_GAUSS, LEAST_SQUARES, % WEIGHTED_LEAST_SQUARES) NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES % % CourantFriedrichsLewy condition of the finest grid CFL_NUMBER= 10 % % 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= ( 0.5, 1.5, 0.01, 1000 ) % % RungeKutta alpha coefficients RK_ALPHA_COEFF= ( 0.66667, 0.66667, 1.000000 ) % % Number of total iterations INNER_ITER= 100000 % % Linear solver for the implicit formulation (BCGSTAB, FGMRES) LINEAR_SOLVER= FGMRES % % Preconditioner of the Krylov linear solver (ILU, JACOBI, LINELET, LU_SGS) LINEAR_SOLVER_PREC= ILU % % Min error of the linear solver for the implicit formulation LINEAR_SOLVER_ERROR= 1E6 % % Max number of iterations of the linear solver for the implicit formulation LINEAR_SOLVER_ITER= 20 %  MULTIGRID PARAMETERS % % % MultiGrid Levels (0 = no multigrid) MGLEVEL= 4 % % Multigrid cycle (V_CYCLE, W_CYCLE, FULLMG_CYCLE) MGCYCLE= W_CYCLE % % Multigrid presmoothing level MG_PRE_SMOOTH= ( 1, 1, 1, 1 ) % % Multigrid postsmoothing 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= 0.5 % % Damping factor for the correction prolongation MG_DAMP_PROLONGATION= 0.5 %  FLOW NUMERICAL METHOD DEFINITION % % % Convective numerical method (JST, LAXFRIEDRICH, 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 (NONE, VENKATAKRISHNAN, VENKATAKRISHNAN_WANG, % BARTH_JESPERSEN, VAN_ALBADA_EDGE) SLOPE_LIMITER_FLOW= NONE % % Coefficient for the limiter (smooth regions) VENKAT_LIMITER_COEFF= 0.02 % % 2nd and 4th order artificial dissipation coefficients JST_SENSOR_COEFF= ( 0.5, 0.02 ) % % Time discretization (RUNGEKUTTA_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 % % Slope limiter (VENKATAKRISHNAN, MINMOD) SLOPE_LIMITER_TURB= VENKATAKRISHNAN % % Time discretization (EULER_IMPLICIT) TIME_DISCRE_TURB= EULER_IMPLICIT %%%%%%%%%%%%%%%%%%%%%%% % COUPLING CONDITIONS %%%%%%%%%%%%%%%%%%%%%%% MARKER_FLUID_LOAD = ( RAMP ) DEFORM_MESH = YES MARKER_DEFORM_MESH = ( RAMP ) DEFORM_STIFFNESS_TYPE = WALL_DISTANCE DEFORM_LINEAR_SOLVER = CONJUGATE_GRADIENT DEFORM_LINEAR_SOLVER_PREC = ILU DEFORM_LINEAR_SOLVER_ERROR = 1E10 DEFORM_LINEAR_SOLVER_ITER = 1000 DEFORM_CONSOLE_OUTPUT = NO %  CONVERGENCE PARAMETERS % % % Convergence criteria (CAUCHY, RESIDUAL) CONV_FIELD= RMS_DENSITY % % Min value of the residual (log10 of the residual) CONV_RESIDUAL_MINVAL= 10 % % 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= 1E10 % HISTORY % % History output groups (use 'SU2_CFD d <config_file>' to view list of available fields) HISTORY_OUTPUT= (ITER, RMS_RES, AERO_COEFF) %  INPUT/OUTPUT INFORMATION % % % Mesh input file MESH_FILENAME= Ramp25_Fine_0_5.cgns % % Mesh input file format (SU2, CGNS, NETCDF_ASCII) MESH_FORMAT= CGNS % % Writing solution file frequency OUTPUT_WRT_FREQ= 250 % % Screen writing frequency SCREEN_WRT_FREQ_INNER= 10 Code:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % SU2 configuration file % % Case description: FSI: Vertical Cantilever in Channel  Structure % % Author: Ruben Sanchez Fernandez % % Institution: TU Kaiserslautern % % Date: 20200205 % % File Version 7.0.2 "Blackbird" % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%% % SOLVER TYPE %%%%%%%%%%%%%%%%%%%%%%% SOLVER = ELASTICITY %%%%%%%%%%%%%%%%%%%%%%% % STRUCTURAL PROPERTIES %%%%%%%%%%%%%%%%%%%%%%% GEOMETRIC_CONDITIONS = LARGE_DEFORMATIONS MATERIAL_MODEL = NEO_HOOKEAN ELASTICITY_MODULUS = 1.13E11 POISSON_RATIO = 0.37 FORMULATION_ELASTICITY_2D = PLANE_STRESS %%%%%%%%%%%%%%%%%%%%%%% % INPUT %%%%%%%%%%%%%%%%%%%%%%% MESH_FORMAT = SU2 MESH_FILENAME = ramp_slender_0_001.su2 %%%%%%%%%%%%%%%%%%%%%%% % BOUNDARY CONDITIONS %%%%%%%%%%%%%%%%%%%%%%% MARKER_CLAMPED = ( LEFT_EDGE, RIGHT_EDGE ) MARKER_PRESSURE = ( LOWER_EDGE, 0) %%%%%%%%%%%%%%%%%%%%%%% % COUPLING CONDITIONS %%%%%%%%%%%%%%%%%%%%%%% MARKER_FLUID_LOAD = ( UPPER_EDGE ) %%%%%%%%%%%%%%%%%%%%%%% % SOLUTION METHOD %%%%%%%%%%%%%%%%%%%%%%% NONLINEAR_FEM_SOLUTION_METHOD = NEWTON_RAPHSON INNER_ITER = 40 %%%%%%%%%%%%%%%%%%%%%%% % CONVERGENCE CRITERIA %%%%%%%%%%%%%%%%%%%%%%% CONV_FIELD = RMS_UTOL, RMS_RTOL, RMS_ETOL CONV_RESIDUAL_MINVAL = 10 %%%%%%%%%%%%%%%%%%%%%%% % LINEAR SOLVER %%%%%%%%%%%%%%%%%%%%%%% LINEAR_SOLVER = CONJUGATE_GRADIENT LINEAR_SOLVER_PREC = ILU LINEAR_SOLVER_ERROR = 1E10 LINEAR_SOLVER_ITER = 1000 % Screen writing frequency SCREEN_WRT_FREQ_INNER = 1 Code:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % SU2 configuration file % % Case description: FSI: Vertical Cantilever in Channel % % Author: Ruben Sanchez Fernandez % % Institution: TU Kaiserslautern % % Date: 20200205 % % File Version 7.0.2 "Blackbird" % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%% % SOLVER TYPE %%%%%%%%%%%%%%%%%%%%%%% SOLVER = MULTIPHYSICS %%%%%%%%%%%%%%%%%%%%%%% % INPUT %%%%%%%%%%%%%%%%%%%%%%% MULTIZONE_MESH = NO CONFIG_LIST = (flowSST.cfg, ramp.cfg) %%%%%%%%%%%%%%%%%%%%%%% % SOLUTION STRATEGY %%%%%%%%%%%%%%%%%%%%%%% MULTIZONE_SOLVER = BLOCK_GAUSS_SEIDEL OUTER_ITER = 1000 %%%%%%%%%%%%%%%%%%%%%%% % CONVERGENCE CRITERIA %%%%%%%%%%%%%%%%%%%%%%% CONV_FIELD = AVG_BGS_RES[0], AVG_BGS_RES[1] CONV_RESIDUAL_MINVAL = 10 %%%%%%%%%%%%%%%%%%%%%%% % Relaxation %%%%%%%%%%%%%%%%%%%%%%% %BGS_RELAXATION= FIXED_PARAMETER %STAT_RELAX_PARAMETER= 0.8 %%%%%%%%%%%%%%%%%%%%%%% % COUPLING CONDITIONS %%%%%%%%%%%%%%%%%%%%%%% MARKER_ZONE_INTERFACE = (RAMP, UPPER_EDGE) %%%%%%%%%%%%%%%%%%%%%%% % OUTPUT %%%%%%%%%%%%%%%%%%%%%%% SCREEN_OUTPUT = (OUTER_ITER, AVG_BGS_RES[0], AVG_BGS_RES[1], DEFORM_MIN_VOLUME[0], DEFORM_ITER[0]) WRT_ZONE_CONV = YES OUTPUT_FILES = (RESTART, PARAVIEW, SURFACE_PARAVIEW, SURFACE_CSV) SOLUTION_FILENAME = solution_fsi_steady RESTART_FILENAME = restart_fsi_steady VOLUME_FILENAME = fsi_steady HISTORY_OUTPUT = ITER, BGS_RES[0], AERO_COEFF[0], BGS_RES[1] WRT_ZONE_HIST = YES CONV_FILENAME= history Last edited by sangeet; April 1, 2021 at 15:39. Reason: Added SU2 version 

April 4, 2021, 12:38 

#2 
Senior Member
Pedro Gomes
Join Date: Dec 2017
Posts: 419
Rep Power: 10 
Thanks for uploading all files, makes it a lot easier.
A common issue with structural problems in SU2 is that normal iterative linear solvers are not strong enough, the 1000 iterations you have with ILU and conjugate gradient barely drop the residuals. If you compile the code with PaStiX you can solve anything (there are instruction in TestCases/pastix_support). The other issue you have is that either the structure is too flexible or there is supposed to be some pressure applied from the other side. I ran it for one outer iteration and the plate becomes a balloon. For FSI the pressure load is applied relative to freestream (P  Pinf) so, as if the "internal" pressure were Pinf. You may need to increase the pressure load on the LOWER_EDGE marker if this is not what you want to simulate. Here are the configs for how I got it to converge. EDIT: with a much larger elasticity modulus. 

April 4, 2021, 14:48 

#3 
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Sangeet
Join Date: Jun 2017
Location: India
Posts: 43
Rep Power: 7 
Thank you for your suggestions. I will try the case with PaStiX.
Also, does it mean that instead of (ppinf) if I want (p) to be load on the solidfluid interface, I should specify the pressure load on the LOWER_EDGE as pinf? 

April 4, 2021, 17:28 

#4 
Senior Member
Pedro Gomes
Join Date: Dec 2017
Posts: 419
Rep Power: 10 
For that it should be pinf because the normal points in the opposite direction.


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