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October 11, 2020, 14:57 
Help wanted for 3d FSI  No coupling

#1 
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California
Join Date: Jan 2019
Posts: 8
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Hi All,
I was doing a 3d FSI on a cantilever column in uniform flow. I used the following configuration files: Sorry about putting them all here in the end of this thread. The issue is that when I check the solution, it seems that the cantilever beam did not bend as expected. The coupling seems to work because I can still see small deformation on the surface of the column at high pressure but there was no bending. I thought the reason is that the fluid mesh did not deform as expected. I wonder why this could happen. There must be something wrong with my mesh deformation in my configuration file. Could someone please help me to look in the configuration file>? Thank you !!!!! My output for the last iteration goes like this: ++  Zone 0 (Incomp. Fluid)  ++  Inner_Iter Time(sec) rms[P] CL CD Avg CFL ++  0 1.4844e+02 8.057513 0.000001 0.000069 2.0000e+04  10 9.3722e+01 8.105184 0.000004 0.000066 2.0000e+04 ++  Zone 1 (Structure)  ++  Inner_Iter Load[%] rms[U] rms[R] rms[E] VonMises ++  0 100.00% 8.207325 3.791529 15.592381 1.4176e+01  99 100.00% 8.655378 3.792181 16.394546 1.4176e+01 ++  Multizone Summary  ++  Outer_Iter avg[bgs][0] avg[bgs][1]MinVolume[0]DeformIter[0 ++  59 0.102389 10.135375 3.7766e14 286 # CG residual history # Residual tolerance target = 1e10 # Initial residual norm = 1.1249e06 0 0.228422 100 5.94382e08 270 1.09e10 # CG final (true) residual: # Iteration = 270: res/res0 = 9.67159e11.  Solver Exit  Maximum number of iterations reached (OUTER_ITER = 60) before convergence. ++  Convergence Field  Value  Criterion  Converged  ++  avg[bgs][0] 0.102389 < 7 No  avg[bgs][1] 10.1354 < 7 Yes +  Exit Success (SU2_CFD)  Here is the configuration file I used: %%%%%%%%%%%%%%%%%%%%%%% %%%%%%. MAIN CONFIG FILE %%%%%%% %%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%% % SOLVER TYPE %%%%%%%%%%%%%%%%%%%%%%% SOLVER = MULTIPHYSICS %%%%%%%%%%%%%%%%%%%%%%% % INPUT %%%%%%%%%%%%%%%%%%%%%%% %MULTIZONE = YES CONFIG_LIST = (hair_m_v0.cfg.cfg, config_hair_str.cfg) MULTIZONE_MESH = NO %%%%%%%%%%%%%%%%%%%%%%% % COUPLING CONDITIONS %%%%%%%%%%%%%%%%%%%%%%% MARKER_ZONE_INTERFACE = (cylwet, structuralwet) %%%%%%%%%%%%%%%%%%%%%%% % SOLUTION STRATEGY %%%%%%%%%%%%%%%%%%%%%%% MULTIZONE_SOLVER = BLOCK_GAUSS_SEIDEL OUTER_ITER = 60 %%%%%%%%%%%%%%%%%%%%%%% % CONVERGENCE CRITERIA %%%%%%%%%%%%%%%%%%%%%%% CONV_FIELD = AVG_BGS_RES[0], AVG_BGS_RES[1] CONV_RESIDUAL_MINVAL = 7 %%%%%%%%%%%%%%%%%%%%%%% % 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) SOLUTION_FILENAME = solution_hair_m0_r1n_fsi_steady RESTART_FILENAME = restart_hair_m0_r1n_fsi_steady VOLUME_FILENAME = hair_m0_r1n_fsi_steady HISTORY_OUTPUT = ITER, BGS_RES[0], AERO_COEFF[0], BGS_RES[1] WRT_ZONE_HIST = YES CONV_FILENAME= history %%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%Sub CONFIG FILE  FLUID%%%%% %%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % Physical governing equations (EULER, NAVIER_STOKES, % WAVE_EQUATION, HEAT_EQUATION, FEM_ELASTICITY, % POISSON_EQUATION) SOLVER= INC_NAVIER_STOKES % % Specify turbulent model (NONE, SA, SA_NEG, SST) KIND_TURB_MODEL= NONE % % Mathematical problem (DIRECT, CONTINUOUS_ADJOINT) MATH_PROBLEM= DIRECT % % Restart solution (NO, YES) % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  VISCOSITY MODEL % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Viscosity model (SUTHERLAND, CONSTANT_VISCOSITY). VISCOSITY_MODEL= CONSTANT_VISCOSITY % % Molecular Viscosity that would be constant (1.716E5 by default) MU_CONSTANT= 1.716E5 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  REFERENCE VALUE DEFINITION % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Reference origin for moment computation REF_ORIGIN_MOMENT_X = 0.00 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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  UNSTEADY SIMULATION % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% TIME_DOMAIN = NO % % Numerical Method for UnsteadNOy simulation(NO, TIME_STEPPING, DUAL_TIME_STEPPING1ST_ORDER, DUAL_TIME_STEPPING2ND_ORDER, TIME_SPECTRAL) %TIME_MARCHING= DUAL_TIME_STEPPING2ND_ORDER % % Time Step for dual time stepping simulations (s) %TIME_STEP= 5e4 % % Maximum Number of physical time steps. %TIME_ITER= 10 % % Number of internal iterations (dual time method) INNER_ITER= 50 % % Restart after the transient phase has passed RESTART_SOL = NO % % Specify unsteady restart iter RESTART_ITER = 0 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  incompressible inlet setting % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % inlet INC_INLET_TYPE = VELOCITY_INLET INC_INLET_DAMPING= 0.1 % outlet INC_OUTLET_TYPE= PRESSURE_OUTLET INC_OUTLET_DAMPING= 0.1 % Density model within the incompressible flow solver. % Options are CONSTANT (default), BOUSSINESQ, or VARIABLE. If VARIABLE, % an appropriate fluid model must be selected. INC_DENSITY_MODEL= CONSTANT % % Solve the energy equation in the incompressible flow solver INC_ENERGY_EQUATION = NO % % Initial density for incompressible flows % (1.2886 kg/m^3 by default (air), 998.2 Kg/m^3 (water)) INC_DENSITY_INIT= 1.2886 FREESTREAM_PRESSURE= 101325.0 % % Initial velocity for incompressible flows (1.0,0,0 m/s by default) INC_VELOCITY_INIT= ( 10.0, 0.0, 0.0 ) % % Initial temperature for incompressible flows that include the % energy equation (288.15 K by default). Value is ignored if % INC_ENERGY_EQUATION is false. INC_TEMPERATURE_INIT= 288.15 % % Nondimensionalization scheme for incompressible flows. Options are % INITIAL_VALUES (default), REFERENCE_VALUES, or DIMENSIONAL. % INC_*_REF values are ignored unless REFERENCE_VALUES is chosen. INC_NONDIM= DIMENSIONAL % % Reference density for incompressible flows (1.0 kg/m^3 by default) INC_DENSITY_REF= 1.0 % % Reference velocity for incompressible flows (1.0 m/s by default) INC_VELOCITY_REF= 1.0 % % Reference temperature for incompressible flows that include the % energy equation (1.0 K by default) INC_TEMPERATURE_REF = 1.0 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  BOUNDARY CONDITION DEFINITION  % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % NavierStokes wall boundary marker(s) (NONE = no marker) MARKER_HEATFLUX= ( cylwet, 0.0, wall, 0.0 ) % % Farfield boundary marker(s) (NONE = no marker) MARKER_FAR= ( top ) % % inlet % Inc. Velocity: (inlet marker, temperature, velocity magnitude, flow_direction_x, % flow_direction_y, flow_direction_z, ... ) where flow_direction is % a unit vector. MARKER_INLET = (inlet, 288.15, 10, 1, 0, 0 ) % % Outlet boundary marker(s) (NONE = no marker) % Compressible: ( outlet marker, back pressure (static thermodynamic), ... ) % Inc. Pressure: ( outlet marker, back pressure (static gauge in Pa), ... ) % Inc. Mass Flow: ( outlet marker, mass flow target (kg/s), ... ) MARKER_OUTLET= ( outlet, 0 ) % % % Marker(s) of the surface to be plotted or designed MARKER_PLOTTING= ( cylwet ) % % Marker(s) of the surface where the functional (Cd, Cl, etc.) will be evaluated MARKER_MONITORING= ( cylwet ) %%%%%%%%%%%%%%%%%%%%%%%%%%%%% % COUPLING CONDITIONS% %%%%%%%%%%%%%%%%%%%%%%%%%%%%% MARKER_FLUID_LOAD = ( cylwet ) DEFORM_MESH = YES MARKER_DEFORM_MESH = ( cylwet ) DEFORM_STIFFNESS_TYPE = WALL_DISTANCE DEFORM_LINEAR_SOLVER = CONJUGATE_GRADIENT DEFORM_LINEAR_SOLVER_PREC = ILU DEFORM_LINEAR_SOLVER_ERROR = 1E10 DEFORM_LINEAR_SOLVER_ITER = 500 DEFORM_CONSOLE_OUTPUT = YES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% %  COMMON PARAMETERS DEFINING THE NUMERICAL METHOD % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %% % Numerical method for spatial gradients (GREEN_GAUSS, WEIGHTED_LEAST_SQUARES) NUM_METHOD_GRAD= GREEN_GAUSS % % CourantFriedrichsLewy condition of the finest grid CFL_NUMBER= 100.0 % % Adaptive CFL number (NO, YES) CFL_ADAPT= YES % % Parameters of the adaptive CFL number (factor down, factor up, CFL min value, % CFL max value ) CFL_ADAPT_PARAM= ( 0.1, 2.0, 0.01, 20000 ) % % RungeKutta alpha coefficients RK_ALPHA_COEFF= ( 0.66667, 0.66667, 1.000000 ) % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  LINEAR SOLVER DEFINITION % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Linear solver for implicit formulations (BCGSTAB, FGMRES) LINEAR_SOLVER= FGMRES % % Preconditioner of the Krylov linear solver (JACOBI, LINELET, LU_SGS) LINEAR_SOLVER_PREC= ILU % % Minimum error of the linear solver for implicit formulations LINEAR_SOLVER_ERROR= 1E10 % % Max number of iterations of the linear solver for the implicit formulation LINEAR_SOLVER_ITER= 100 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  SLOPE LIMITER DEFINITION % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Coefficient for the limiter VENKAT_LIMITER_COEFF= 0.1 % % Coefficient for the sharp edges limiter ADJ_SHARP_LIMITER_COEFF= 3.0 % % Reference coefficient (sensitivity) for detecting sharp edges. REF_SHARP_EDGES= 3.0 % % Remove sharp edges from the sensitivity evaluation (NO, YES) SENS_REMOVE_SHARP= NO % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  MULTIGRID PARAMETERS % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % MultiGrid Levels (0 = no multigrid) MGLEVEL= 2 % % Multigrid cycle (V_CYCLE, W_CYCLE, FULLMG_CYCLE) MGCYCLE= V_CYCLE % % Multigrid presmoothing level MG_PRE_SMOOTH= ( 1, 2, 3, 3 ) % % 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= 0.8 % % Damping factor for the correction prolongation MG_DAMP_PROLONGATION= 0.8 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  FLOW NUMERICAL METHOD DEFINITION % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Convective numerical method (JST, LAXFRIEDRICH, CUSP, ROE, AUSM, HLLC, % TURKEL_PREC, MSW) CONV_NUM_METHOD_FLOW= FDS % % 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= VENKATAKRISHNAN % % % 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 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  CONVERGENCE PARAMETERS % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Convergence criteria (CAUCHY, RESIDUAL) CONV_FIELD= RMS_PRESSURE % % 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= 1E6 % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %  INPUT/OUTPUT INFORMATION % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % Mesh input file MESH_FILENAME= hairmfluidr2n.su2 % % Mesh input file format (SU2, CGNS, NETCDF_ASCII) MESH_FORMAT= SU2 % % Mesh output file MESH_OUT_FILENAME= hairmfluidr2n.su2 % % Restart flow input file SOLUTION_FILENAME= hairmfluidr2n.dat % % Restart adjoint input file SOLUTION_ADJ_FILENAME= hairmfluidr2n.dat % % Output file format (PARAVIEW, TECPLOT, STL) TABULAR_FORMAT= CSV % % output file % % Output file convergence history (w/o extension) CONV_FILENAME= hairmfluidr2n_history %%%%%%%%%%%%%%%%%%%%%%%%%% %%%%% SubConfig SOLID PART%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%% % SOLVER TYPE %%%%%%%%%%%%%%%%%%%%%%% SOLVER = ELASTICITY %%%%%%%%%%%%%%%%%%%%%%% % STRUCTURAL PROPERTIES %%%%%%%%%%%%%%%%%%%%%%% GEOMETRIC_CONDITIONS = LARGE_DEFORMATIONS MATERIAL_MODEL = NEO_HOOKEAN %ELASTICITY_MODULUS = (0.5E6, 1.6E11) %POISSON_RATIO = (0.49, 0.0) %MATERIAL_DENSITY = (960,7500) ELASTICITY_MODULUS = (0.5E5) POISSON_RATIO = (0.49) %MATERIAL_DENSITY = (960) % FORMULATION_ELASTICITY_2D = PLANE_STRAIN %%%%%%%%%%%%%%%%%%%%%%% % INPUT %%%%%%%%%%%%%%%%%%%%%%% MESH_FORMAT = SU2 MESH_FILENAME = hairmstructuralr2n.su2 %FEA_FILENAME = element_prop.dat %%%%%%%%%%%%%%%%%%%%%%% % BOUNDARY CONDITIONS %%%%%%%%%%%%%%%%%%%%%%% MARKER_CLAMPED = ( clamped ) MARKER_PRESSURE = ( structuralwet, 0) %%%%%%%%%%%%%%%%%%%%%%% %% BODY FORCE %%%%%%%%%%%%%%%%%%%%%%% % %BODY_FORCE = YES %BODY_FORCE_VECTOR = (0.0, 9.81, 0.0) %%%%%%%%%%%%%%%%%%%%%%% % COUPLING CONDITIONS %%%%%%%%%%%%%%%%%%%%%%% MARKER_FLUID_LOAD = ( structuralwet ) %%%%%%%%%%%%%%%%%%%%%%% % SOLUTION METHOD %%%%%%%%%%%%%%%%%%%%%%% NONLINEAR_FEM_SOLUTION_METHOD = NEWTON_RAPHSON INNER_ITER = 100 INCREMENTAL_LOAD = YES NUMBER_INCREMENTS = 5 INCREMENTAL_CRITERIA = (1.0, 1.0, 1.0) %%%%%%%%%%%%%%%%%%%%%%% % CONVERGENCE CRITERIA METHOD %%%%%%%%%%%%%%%%%%%%%%% CONV_FIELD = RMS_UTOL, RMS_RTOL, RMS_ETOL CONV_RESIDUAL_MINVAL = 7 %%%%%%%%%%%%%%%%%%%%%%% % LINEAR SOLVER %%%%%%%%%%%%%%%%%%%%%%% LINEAR_SOLVER = CONJUGATE_GRADIENT LINEAR_SOLVER_PREC = ILU LINEAR_SOLVER_ERROR = 1E8 LINEAR_SOLVER_ITER = 400 %%%%%%%%%%%%%%%%%%%%%%% % OUTPUT %%%%%%%%%%%%%%%%%%%%%%% SCREEN_OUTPUT = (INNER_ITER, LOAD_INCREMENT, RMS_UTOL, RMS_RTOL, RMS_ETOL, VMS) SCREEN_WRT_FREQ_INNER = 1 

October 12, 2020, 05:55 

#2 
Senior Member
Pedro Gomes
Join Date: Dec 2017
Posts: 250
Rep Power: 6 
At first glance all looks ok.
Can you post some pictures? Keep in mind that the structural result is always undeformed, you need to apply the deformation (displacements) in postprocessing if you want. In Paraview this is done with the "warp" function. Also, what version of SU2 are you using? 

October 14, 2020, 13:11 

#3  
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California
Join Date: Jan 2019
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Quote:
Hi PCG, Thank you for your respond. The flow field and the corresponding pressure distribution on the surface, along with y+, are all what I expected. However, the force seems not to be transmitted into the solid calculation as only a few mesh nodes were shifted to cause stress on the cantilever. In addition, there was no bending observed. Fluid domain, notice that no mesh movement> 13265327.png surface pressure: 922624236.jpg Vonmises stress on column 1479390492.jpg To verify the problem is not due to structural mesh. I did a separate simulation using same mesh file but in steady loading of uniform 100 Pa in +x direction from 1 side of the column for the solid only. The deformation met my expectation. 999.jpg I do think there is something wrong within my coupling or mesh deformation for fluid domain. I don't know what that is however. I was using Release 7.0.4. I was using a standard OH grid for this fluid domain. 

October 14, 2020, 17:44 

#4 
Senior Member
Pedro Gomes
Join Date: Dec 2017
Posts: 250
Rep Power: 6 
I don't see anything major in your config.
There are some options that are not necessary or slightly misplaced but I don't think they would cause issues. Anyway, I modified one of the 2D examples to use the incompressible NS solver (attached), it runs and deforms try to adapt the configs to your grid and see if it works. 

October 16, 2020, 07:02 

#5  
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Quote:
Thank you for your reply. I had done a 2D case before using modified tutorial file and it works great. However, in my 3d case, it seems that the coupling went wrong. As you pointed out, my config file looks okay. So I wonder if the convergence is the reason that the pressure coupling seems to failed. I wonder what should be the convergence criteria for the mesh deformation, solid as well as fluid. I was aiming at E(6) for fluid and solid, but not sure what should be the minimum residual error for mesh deformation solver. In addition, by looking at the output from my last iteration: ++  Zone 0 (Incomp. Fluid)  ++  Inner_Iter Time(sec) rms[P] CL CD Avg CFL ++  0 1.4844e+02 8.057513 0.000001 0.000069 2.0000e+04  10 9.3722e+01 8.105184 0.000004 0.000066 2.0000e+04 ++  Zone 1 (Structure)  ++  Inner_Iter Load[%] rms[U] rms[R] rms[E] VonMises ++  0 100.00% 8.207325 3.791529 15.592381 1.4176e+01  99 100.00% 8.655378 3.792181 16.394546 1.4176e+01 ++  Multizone Summary  ++  Outer_Iter avg[bgs][0] avg[bgs][1]MinVolume[0]DeformIter[0 ++  59 0.102389 10.135375 3.7766e14 286 # CG residual history # Residual tolerance target = 1e10 # Initial residual norm = 1.1249e06 0 0.228422 100 5.94382e08 270 1.09e10 # CG final (true) residual: # Iteration = 270: res/res0 = 9.67159e11.  Solver Exit  Maximum number of iterations reached (OUTER_ITER = 60) before convergence. ++  Convergence Field  Value  Criterion  Converged  ++  avg[bgs][0] 0.102389 < 7 No  avg[bgs][1] 10.1354 < 7 Yes does these convergence raise red flag? To me it is. Is the "failed coupling" actually due to poor convergence? Thank you again. 

October 16, 2020, 18:14 

#6 
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Pedro Gomes
Join Date: Dec 2017
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Rep Power: 6 
The example I provided follows what I consider to be best practices for FSI, 2D or 3D.
There is no mesh deformation on the solid side. You specified a Poison ratio of 0.49 for the structure, this makes the equations very illconditioned, especially in 3D. You should never need more than 10 inner iterations on the structure, if with 100 iterations the residuals do not drop it means the linear solver is not able to solve the systems. 

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