[lalatuobu]

Hi,

I was trying to do a unsteady fsi problem in SU2. Before unsteady simulation, I had issues for the steady solution. I was basically following the fsi steady tutorial in the SU2 tutorial except I re-created my own mesh in Pointwise, and changed some BCs and material properties to mimic my application.

https://su2code.github.io/tutorials/Static_FSI/



However, I always get the following error code after executing few outer iterations.


Error in "void CSysSolve<double>::ModGramSchmidt(int, vector<vector<ScalarType> > &, vector<CSysVector<ScalarType> > &) const [ScalarType = double]":
-------------------------------------------------------------------------
FGMRES orthogonalization failed, linear solver diverged.
------------------------------ Error Exit -------------------------------



I printed out the inner-loop output, it seems that the problem lies in the structural linear solver. After few iterations, the screen output become:


# CG residual history
# Residual tolerance target = 1e-08
# Initial residual norm = 653.158
0 2.22439
10 0.00436788
20 0.00105218
30 0.000474043
40 0.000183201
50 6.82945e-05
60 3.57483e-05
70 1.84961e-05
80 9.06388e-06
90 3.03924e-06
100 1.05806e-06
110 2.90883e-07
120 8.66932e-08
130 2.04726e-08
# CG final (true) residual:
# Iteration = 135: |res|/|res0| = 9.50867e-09.

+----------------------------------------------------------------+
| Zone 0 (Incomp. Fluid) |
+----------------------------------------------------------------+
| Outer_Iter| Inner_Iter| rms[P]| rms[U]| rms[V]|
+----------------------------------------------------------------+
| 9| 0| -3.142056| -1.707746| -1.821803|
| 9| 20| -3.642543| -1.759277| -1.855988|
| 9| 40| -3.677550| -1.758297| -1.872853|
| 9| 60| -3.717325| -1.741693| -1.868771|
| 9| 80| -3.744304| -1.718225| -1.866626|
| 9| 100| -3.726701| -1.691568| -1.868913|
| 9| 120| -3.709504| -1.663673| -1.851842|
| 9| 140| -3.684008| -1.629814| -1.835092|
| 9| 160| -3.653019| -1.596141| -1.812889|
| 9| 180| -3.624896| -1.563961| -1.783655|
| 9| 200| -3.592057| -1.536577| -1.755740|
| 9| 220| -3.552223| -1.517839| -1.720308|
| 9| 240| -3.543369| -1.492790| -1.688864|
| 9| 260| -3.538167| -1.468293| -1.663987|
| 9| 280| -3.550885| -1.444629| -1.647335|
| 9| 300| -3.580128| -1.427568| -1.630473|
| 9| 320| -3.595646| -1.417964| -1.616398|
| 9| 340| -3.602372| -1.407468| -1.618355|
| 9| 360| -3.609427| -1.393281| -1.637197|
| 9| 380| -3.604804| -1.379942| -1.666958|
| 9| 400| -3.612665| -1.367395| -1.695200|
| 9| 420| -3.613693| -1.360901| -1.712291|
| 9| 440| -3.601209| -1.361126| -1.710941|
| 9| 460| -3.580616| -1.364588| -1.697890|
| 9| 480| -3.560080| -1.369603| -1.685052|
| 9| 500| -3.545734| -1.374779| -1.681143|
| 9| 520| -3.541468| -1.380101| -1.674003|
| 9| 540| -3.542229| -1.384182| -1.663407|
| 9| 560| -3.541609| -1.385249| -1.659417|
| 9| 580| -3.532399| -1.385980| -1.666169|
| 9| 600| -3.520539| -1.389261| -1.677467|
| 9| 620| -3.516180| -1.395652| -1.681080|
| 9| 640| -3.521221| -1.403373| -1.673044|
| 9| 660| -3.530227| -1.409500| -1.664122|
| 9| 680| -3.534119| -1.412020| -1.668841|
| 9| 700| -3.536955| -1.409113| -1.683965|
| 9| 720| -3.539968| -1.400793| -1.703749|
| 9| 740| -3.544609| -1.388075| -1.713818|
| 9| 760| -3.553732| -1.372998| -1.699195|
| 9| 780| -3.566625| -1.357649| -1.670340|
| 9| 800| -3.582853| -1.341852| -1.646002|
| 9| 820| -3.598614| -1.324911| -1.635735|
| 9| 840| -3.609240| -1.305784| -1.637410|
| 9| 860| -3.619109| -1.282653| -1.638490|
| 9| 880| -3.633452| -1.256368| -1.628953|
| 9| 900| -3.650786| -1.230435| -1.605689|
| 9| 920| -3.662310| -1.205930| -1.578776|
| 9| 940| -3.658838| -1.181203| -1.564011|
| 9| 960| -3.648898| -1.154774| -1.559276|
| 9| 980| -3.647128| -1.126993| -1.549837|
| 9| 999| -3.655594| -1.101131| -1.530044|
+-----------------------------------------------------------------------------+
| Zone 1 (Structure) |
+-----------------------------------------------------------------------------+
| Outer_Iter| Inner_Iter| rms[U]| rms[R]| rms[E]| VonMises|
+-----------------------------------------------------------------------------+
| 9| 0| -0.176796| 4.192294| 2.453922| 2.8349e+05|

Incremental load: increment 1
+-----------------------------------------------------------------------------+
| Zone 1 (Structure) |
+-----------------------------------------------------------------------------+
| Outer_Iter| Inner_Iter| rms[U]| rms[R]| rms[E]| VonMises|
+-----------------------------------------------------------------------------+
| 9| 0| -0.268120| 2.584196| 1.413370| 5.0003e+04|
| 9| 10| nan| nan| nan| 0.0000e+00|
| 9| 20| nan| nan| nan| 0.0000e+00|
| 9| 30| nan| nan| nan| 0.0000e+00|
| 9| 40| nan| nan| nan| 0.0000e+00|
| 9| 50| nan| nan| nan| 0.0000e+00|
| 9| 60| nan| nan| nan| 0.0000e+00|
| 9| 70| nan| nan| nan| 0.0000e+00|
| 9| 80| nan| nan| nan| 0.0000e+00|
| 9| 90| nan| nan| nan| 0.0000e+00|
| 9| 99| nan| nan| nan| 0.0000e+00|

Incremental load: increment 2

Notice that I was using incremental loading condition to resolve the large deformation issue. I tried to change FGMRES settings but none of these setting could help to resolve the issue.
I also checked the flow field and deformation before exploding, and it seems reasonable to me (see attachment). I was using INC-NS



I wonder if anyone can help me to take a look into this issue?



btw: here is the config file used:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% SU2 configuration file %
% Case description: FSI: Vertical Cantilever in Channel %
% Author: Ruben Sanchez Fernandez %
% Institution: TU Kaiserslautern %
% Date: 2020-02-05 %
% File Version 7.0.2 "Blackbird" %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%
% SOLVER TYPE
%%%%%%%%%%%%%%%%%%%%%%%

SOLVER = MULTIPHYSICS

%%%%%%%%%%%%%%%%%%%%%%%
% INPUT
%%%%%%%%%%%%%%%%%%%%%%%

MULTIZONE_MESH = NO
CONFIG_LIST = (config_channel.cfg, config_cantilever.cfg)

RESTART_SOL = NO
RESTART_ITER = 1

%%%%%%%%%%%%%%%%%%%%%%%
% SOLUTION STRATEGY
%%%%%%%%%%%%%%%%%%%%%%%
TIME_DOMAIN = NO

%TIME_MARCHING = DUAL_TIME_STEPPING-1ST_ORDER

%TIME_STEP = 5e-3

%TIME_ITER = 10

INNER_ITER = 500

%TIME_DISCRE_FLOW = EULER_IMPLICIT

MULTIZONE_SOLVER = BLOCK_GAUSS_SEIDEL
OUTER_ITER = 20

%%%%%%%%%%%%%%%%%%%%%%%
% COUPLING CONDITIONS
%%%%%%%%%%%%%%%%%%%%%%%

MARKER_ZONE_INTERFACE = (wet, wets)

%%%%%%%%%%%%%%%%%%%%%%%
% CONVERGENCE CRITERIA
%%%%%%%%%%%%%%%%%%%%%%%

CONV_FIELD = AVG_BGS_RES[0], AVG_BGS_RES[1]
CONV_RESIDUAL_MINVAL = -5

%%%%%%%%%%%%%%%%%%%%%%%
% 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 = restart_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 = NO
CONV_FILENAME= history

***********************************************
***********************************************
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% SU2 configuration file %
% Case description: FSI: Vertical Cantilever in Channel - Flow %
% Author: Ruben Sanchez Fernandez %
% Institution: TU Kaiserslautern %
% Date: 2020-02-05 %
% File Version 7.0.2 "Blackbird" %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%
% SOLVER TYPE
%%%%%%%%%%%%%%%%%%%%%%%

SOLVER = INC_NAVIER_STOKES

%%%%%%%%%%%%%%%%%%%%%%%
% FLOW PROPERTIES
%%%%%%%%%%%%%%%%%%%%%%%

INC_NONDIM = INITIAL_VALUES
INC_DENSITY_MODEL = CONSTANT

INC_DENSITY_INIT = 1.28
INC_TEMPERATURE_INIT = 300
INC_VELOCITY_INIT = ( 10.0, 0.0, 0.0 )

INC_DENSITY_REF = 1.0
INC_VELOCITY_REF = 1.0
INC_TEMPERATURE_REF = 1.0

VISCOSITY_MODEL = CONSTANT_VISCOSITY
MU_CONSTANT = 16.82e-6
MU_REF= 1.716E-5
FREESTREAM_VISCOSITY= 1.853E-5


%%%%%%%%%%%%%%%%%%%%%%%
% INPUT
%%%%%%%%%%%%%%%%%%%%%%%

MESH_FORMAT = SU2
MESH_FILENAME = flowfield.su2

%%%%%%%%%%%%%%%%%%%%%%%
% BOUNDARY CONDITIONS
%%%%%%%%%%%%%%%%%%%%%%%




MARKER_HEATFLUX = ( wet, 0.0, base, 0.0)
MARKER_EULER = (ff)
INC_INLET_TYPE = VELOCITY_INLET
INC_OUTLET_TYPE = PRESSURE_OUTLET

MARKER_INLET = ( inlet, 0.0, 10.0, 1.0, 0.0, 0.0 )
MARKER_OUTLET = ( outlet, 0.0 )

MARKER_MONITORING = ( wet )

%%%%%%%%%%%%%%%%%%%%%%%
% COUPLING CONDITIONS
%%%%%%%%%%%%%%%%%%%%%%%

MARKER_FLUID_LOAD = ( wet )

DEFORM_MESH = YES
MARKER_DEFORM_MESH = ( wet )

DEFORM_STIFFNESS_TYPE = WALL_DISTANCE
DEFORM_LINEAR_SOLVER = CONJUGATE_GRADIENT
DEFORM_LINEAR_SOLVER_PREC = ILU
DEFORM_LINEAR_SOLVER_ERROR = 1E-8
DEFORM_LINEAR_SOLVER_ITER = 2000
DEFORM_CONSOLE_OUTPUT = YES

%%%%%%%%%%%%%%%%%%%%%%%
% SOLUTION METHOD
%%%%%%%%%%%%%%%%%%%%%%%


INNER_ITER = 1000


%%%%%%%%%%%%%%%%%%
% NUMERICAL METHODS
%%%%%%%%%%%%%%%%%%%

NUM_METHOD_GRAD = WEIGHTED_LEAST_SQUARES
CFL_NUMBER = 3

CONV_NUM_METHOD_FLOW = FDS
MUSCL_FLOW = YES
SLOPE_LIMITER_FLOW = NONE

%%%%%%%%%%%%%%%%%%%%%%%
% REFERCENCE VALUES
%%%%%%%%%%%%%%%%%%%%%%%

REF_ORIGIN_MOMENT_X = 0.00
REF_ORIGIN_MOMENT_Y = 0.00
REF_ORIGIN_MOMENT_Z = 0.00

REF_LENGTH = 0.01
REF_AREA = 0.01

%%%%%%%%%%%%%%%%%%%%%%%
% CONVERGENCE CRITERIA
%%%%%%%%%%%%%%%%%%%%%%%

CONV_CRITERIA = RESIDUAL
CONV_FIELD = RMS_PRESSURE, RMS_VELOCITY-X, RMS_VELOCITY-Y, FORCE-X, FORCE-Y
CONV_RESIDUAL_MINVAL = -12

CONV_STARTITER = 10
CONV_CAUCHY_ELEMS = 100
CONV_CAUCHY_EPS = 1E-6

%%%%%%%%%%%%%%%%%%%%%%%
% LINEAR SOLVER
%%%%%%%%%%%%%%%%%%%%%%%

LINEAR_SOLVER = FGMRES
LINEAR_SOLVER_PREC = ILU
LINEAR_SOLVER_ERROR = 1E-10
LINEAR_SOLVER_ITER = 1000

SCREEN_WRT_FREQ_INNER = 20

****************************************
****************************************
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% SU2 configuration file %
% Case description: FSI: Vertical Cantilever in Channel - Structure %
% Author: Ruben Sanchez Fernandez %
% Institution: TU Kaiserslautern %
% Date: 2020-02-05 %
% File Version 7.0.2 "Blackbird" %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%
% SOLVER TYPE
%%%%%%%%%%%%%%%%%%%%%%%

SOLVER = ELASTICITY

%%%%%%%%%%%%%%%%%%%%%%%
% STRUCTURAL PROPERTIES
%%%%%%%%%%%%%%%%%%%%%%%

GEOMETRIC_CONDITIONS = LARGE_DEFORMATIONS
MATERIAL_MODEL = NEO_HOOKEAN

ELASTICITY_MODULUS = 0.5E6
POISSON_RATIO = 0.49
FORMULATION_ELASTICITY_2D = PLANE_STRAIN

%%%%%%%%%%%%%%%%%%%%%%%
% INPUT
%%%%%%%%%%%%%%%%%%%%%%%

MESH_FORMAT = SU2
MESH_FILENAME = structure.su2

%%%%%%%%%%%%%%%%%%%%%%%
% BOUNDARY CONDITIONS
%%%%%%%%%%%%%%%%%%%%%%%

MARKER_CLAMPED = ( base )
MARKER_PRESSURE = ( wets, 0)

%%%%%%%%%%%%%%%%%%%%%%%
% COUPLING CONDITIONS
%%%%%%%%%%%%%%%%%%%%%%%

MARKER_FLUID_LOAD = ( wets )

%%%%%%%%%%%%%%%%%%%%%%%
% SOLUTION METHOD
%%%%%%%%%%%%%%%%%%%%%%%

NONLINEAR_FEM_SOLUTION_METHOD = NEWTON_RAPHSON


INNER_ITER = 100


INCREMENTAL_LOAD = YES
NUMBER_INCREMENTS = 40
INCREMENTAL_CRITERIA = (2.0, 2.0, 2.0)



%%%%%%%%%%%%%%%%%%%%%%%
% 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 = 1E-10
LINEAR_SOLVER_ITER = 1000


SCREEN_WRT_FREQ_INNER = 20