[WilliamH]

Hi all,
I am new to SU2 and I am attempting to find a CFD solution including oblique shocks in a scramjet inlet. I created a mesh using Gmsh which I can't attach here. I have also written a configuration file.
However, when I try to run it, it tells me that SU2 has diverged.
If someone could take a look at my mesh and configuration files and tell me what errors there are. Again, I am very new to this so there could be many!

I added a picture of the inlet scramjet for a better understanding.

here is the script of my conf file:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% SU2 configuration file %
% Case description: Scramjet inlet (M1 = 5.1) %
% Author: William Haigh %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% ------------- DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION ------------%
%
% Physical governing equations (EULER, NAVIER_STOKES,
% TNE2_EULER, TNE2_NAVIER_STOKES,
% WAVE_EQUATION, HEAT_EQUATION, LINEAR_ELASTICITY,
% POISSON_EQUATION)
SOLVER = EULER

% Specify turbulent model (NONE, SA, SA_NEG, SST)
KIND_TURB_MODEL = NONE

% Mathematical problem (DIRECT, ADJOINT, LINEARIZED)
MATH_PROBLEM = DIRECT

% Restart solution (NO, YES)
RESTART_SOL = NO


% -------------------- COMPRESSIBLE FARFIELD DEFINITION --------------------%

% Mach number (non-dimensional, based on the free-stream values)
MACH_NUMBER = 5.1

% Angle of attack (degrees, only for compressible flows)
AoA = 0.0

% Init option to choose between Reynolds (default) or thermodynamics quantities
% for initializing the solution (REYNOLDS, TD_CONDITIONS)
INIT_OPTION = TD_CONDITIONS

% Free-stream option to choose between density and temperature (default) for
% initializing the solution (TEMPERATURE_FS, DENSITY_FS)
FREESTREAM_OPTION = TEMPERATURE_FS

% Free-stream pressure (101325.0 N/m^2, 2116.216 psf by default)
FREESTREAM_PRESSURE = 4488.0

% Free-stream temperature (288.15 K, 518.67 R by default)
FREESTREAM_TEMPERATURE = 217.92

% Reynolds length (1 m by default)
REYNOLDS_LENGTH = 1.0

% ---------------------- 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= 1.0
%
% Reference area for force coefficients (0 implies automatic calculation)
REF_AREA= 1.0

% ------------------------- IDEAL GAS PROPERTIES -----------------------------%

% Different gas model (STANDARD_AIR, IDEAL_GAS, VW_GAS, PR_GAS)
FLUID_MODEL = IDEAL_GAS

% Ratio of specific heats (1.4 default and the value is hardcoded for the model STANDARD_AIR)
GAMMA_VALUE = 1.4

% Specific gas constant (287.058 J/kg*K default, hardcoded for model STANDARD_AIR)
GAS_CONSTANT = 287

% -------------------- BOUNDARY CONDITION DEFINITION --------------------------%

% Euler wall boundary marker(s) (NONE = no marker)
MARKER_EULER = ( Wall )

% Supersonic inlet boundary marker(s) (NONE = no marker)
% Format: (inlet marker, temperature, static pressure, velocity_x,
% velocity_y, velocity_z, ...) i.e. primitive variables specified
MARKER_SUPERSONIC_INLET = ( Inlet, 217.92, 4488, 1509.119697, 0.0, 0.0)

% Supersonic outlet boundary marker(s) (NONE = no marker)
MARKER_SUPERSONIC_OUTLET = ( Outlet )

% ------------------------ SURFACES IDENTIFICATION ----------------------------%

% Marker(s) of the surface to be plotted or designed
MARKER_PLOTTING = ( Wall )

% Marker(s) of the surface where the functional (Cd, Cl, etc.) will be evaluated
MARKER_MONITORING = ( Wall )

% ------------- COMMON PARAMETERS DEFINING THE NUMERICAL METHOD ---------------%
%
% Numerical method for spatial gradients (GREEN_GAUSS, LEAST_SQUARES,
% WEIGHTED_LEAST_SQUARES)
NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES
%
% Courant-Friedrichs-Lewy condition of the finest grid
CFL_NUMBER= 2
%
% 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= ( 0.1, 2.0, 1, 1e10 )
%
% Runge-Kutta alpha coefficients
RK_ALPHA_COEFF= ( 0.66667, 0.66667, 1.000000 )
%
% Number of total iterations
ITER= 5000
%
% 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= 1E-6
%
% Max number of iterations of the linear solver for the implicit formulation
LINEAR_SOLVER_ITER= 20

% -------------------------- 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 = 1.0

% Damping factor for the correction prolongation
MG_DAMP_PROLONGATION = 1.0

% -------------------- FLOW NUMERICAL METHOD DEFINITION -----------------------%
%
% Convective numerical method (JST, LAX-FRIEDRICH, CUSP, ROE, AUSM, HLLC,
% TURKEL_PREC, MSW)
CONV_NUM_METHOD_FLOW= HLLC
%
% 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= 0.006
%
% 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= RUNGE-KUTTA_EXPLICIT

% --------------------------- CONVERGENCE PARAMETERS --------------------------%
%
% Convergence criteria (CAUCHY, RESIDUAL)
CONV_FIELD= RMS_DENSITY
%
% Min value of the residual (log10 of the residual)
CONV_RESIDUAL_MINVAL= -13
%
% 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-10

% ------------------------- INPUT/OUTPUT INFORMATION --------------------------%

% Mesh input file
MESH_FILENAME = triangless.su2

%Mesh input file format (SU2, CGNS, NETCDF_ASCII)
MESH_FORMAT = SU2

% Mesh output file
MESH_OUT_FILENAME = my_mesh_out.su2

% Restart flow input file
SOLUTION_FILENAME = restart.dat

% Output file format (PARAVIEW, TECPLOT, STL)
OUTPUT_FILES = PARAVIEW_ASCII

% Output file convergence history (w/o extension)
CONV_FILENAME = history

% Output file restart flow
RESTART_FILENAME = restart.dat

% Output file flow (w/o extension) variables
VOLUME_FILENAME = Flow_OS

% Output file surface flow coefficient (w/o extension)
SURFACE_FILENAME = surface

% Writing solution file frequency
WRT_SOL_FREQ = 100

% Writing convergence history frequency
WRT_CON_FREQ = 1

[pcg]

Use EULER_IMPLICIT instead of RK explicit.
Use the VENKATAKRISHNAN_WANG limiter with coeff ~0.05 or the VAN_ALBADA_EDGE.

I don't have much experience with very high speed flows, but you may also try other schemes like AUSM+up or SLAU (if you do set USE_ACCURATE_FLUX_JACOBIANS=YES as it may allow you to run at higher CFL). More info here: https://su2code.github.io/docs_v7/Convective-Schemes/

For a well posed problem with upwind schemes, 20 linear solver iterations is wasteful, 5-10 should be all you need, or linear solver tolerance 0.05 to 0.01.

[WilliamH]

Thank you for your tips I have tried to apply them but I was still having some errors.
Do you think I could send you the mesh I am using to take a look at it?
I suspect that this might be the problem.
Thanks!

[pcg]

SU2 prints some mesh statistics and sanity checks, if you post the screen output for your case I can help you decode that information.

[WilliamH]

This is what I obtain:
------------------- Geometry Preprocessing ( Zone 0 ) -------------------
Two dimensional problem.
14951 grid points.
14625 volume elements.
3 surface markers.
100 boundary elements in index 0 (Marker = inlet).
25 boundary elements in index 1 (Marker = outlet).
525 boundary elements in index 2 (Marker = wall).
14625 quadrilaterals.
Setting point connectivity.
Renumbering points (Reverse Cuthill McKee Ordering).
Recomputing point connectivity.
Setting element connectivity.
Checking the numerical grid orientation.
There has been a re-orientation of 12500 QUADRILATERAL volume elements.
There has been a re-orientation of 650 LINE surface elements.
Identifying edges and vertices.
Computing centers of gravity.
Setting the control volume structure.
Area of the computational grid: 0.97909.
Searching for the closest normal neighbors to the surfaces.
Storing a mapping from global to local point index.
Compute the surface curvature.
Max K: 269.383. Mean K: 2.87427. Standard deviation K: 22.7089.
Checking for periodicity.
Computing mesh quality statistics for the dual control volumes.
+--------------------------------------------------------------+
| Mesh Quality Metric| Minimum| Maximum|
+--------------------------------------------------------------+
| Orthogonality Angle (deg.)| 45.0981| 90|
| CV Face Area Aspect Ratio| 1.11916| 9.17412|
| CV Sub-Volume Ratio| 1| 6.09331|
+--------------------------------------------------------------+

[pcg]

Statistics look ok, it should not be a mesh problem.

[WilliamH]

Thanks for all of your help!

[Praveen_krish]

So were you able to figure it out? what was causing the divergence and what was the solution?

[bigfootedrockmidget]

Originally Posted by Praveen_krish

So were you able to figure it out? what was causing the divergence and what was the solution?

If you are experiencing convergence issues, please create a new post with details of your specific case so we can help you. Also make sure to use the latest SU2 version.