[Batu]

Hello everyone,

I am new at SU2 and am trying to investigate the behavior of RAE 2822 at M=0,8 and 1,3 with different AoA(I am using o-mesh). However, my results do not come similar to my reference. I thought maybe my solver was wrong then tried it with M=0,66 and 0,729 but I took correct answers for those values. Also, I tried both initial options but still couldn't get the right results. So I couldn't find any solution can anybody help me?
Thanks a lot
My cfg file is like that;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% SU2 configuration file %
% Case description: Transonic simulation RAE2822 (RANS) %
% Author: Francisco Palacios %
% Institution: Stanford University %
% Date: 5/15/2013 %
% File Version 7.0.6 "Blackbird" %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% ------------- 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
%
% Init option to choose between Reynolds (default) or thermodynamics quantities
% for initializing the solution (REYNOLDS, TD_CONDITIONS)
INIT_OPTION= TD_CONDITIONS
% 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=0.8
%
% Angle of attack (degrees, only for compressible flows)
AOA=5.00
%
% Free-stream temperature (288.15 K by default)
FREESTREAM_TEMPERATURE= 298.15
%
% Reynolds number (non-dimensional, based on the free-stream values)
REYNOLDS_NUMBER= 17740149.26987561
% Free-stream density (1.2886 Kg/m^3, 0.0025 slug/ft^3 by default)
FREESTREAM_DENSITY= 1.225

% Free-stream viscosity (1.853E-5 N s/m^2, 3.87E-7 lbf s/ft^2 by default)
FREESTREAM_VISCOSITY= 1.52E-5
%
% 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

REF_DIMENSIONALIZATION= FREESTREAM_VEL_EQ_ONE

% -------------------- BOUNDARY CONDITION DEFINITION --------------------------%
%
% Navier-Stokes wall boundary marker(s) (NONE = no marker)
MARKER_HEATFLUX= ( airfoil, 0.0 )
%
% Farfield boundary marker(s) (NONE = no marker)
MARKER_FAR= ( farfield)
%
% Marker(s) of the surface to be plotted or designed
MARKER_PLOTTING= ( airfoil)
%
% Marker(s) of the surface where the functional (Cd, Cl, etc.) will be evaluated
MARKER_MONITORING= ( airfoil )


% ------------- COMMON PARAMETERS DEFINING THE NUMERICAL METHOD ---------------%
%
% Numerical method for spatial gradients (GREEN_GAUSS, WEIGHTED_LEAST_SQUARES)
NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES
NUM_METHOD_GRAD_RECON= LEAST_SQUARES
%
% Courant-Friedrichs-Lewy 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= ( 0.01, 2, 0.0001, 1000 )
%
% Number of total iterations
ITER= 99999
%
% Linear solver for the implicit formulation (BCGSTAB, FGMRES)
LINEAR_SOLVER= FGMRES
%
% Min error of the linear solver for the implicit formulation
LINEAR_SOLVER_ERROR= 1E-4
%
% Max number of iterations of the linear solver for the implicit formulation
LINEAR_SOLVER_ITER= 5

% -------------------------- 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= ROE
%
% 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= 0.05
%
% 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


% --------------------------- CONVERGENCE PARAMETERS --------------------------%
%
% Convergence criteria (CAUCHY, RESIDUAL)
%
CONV_FIELD= LIFT
%
%
% Min value of the residual (log10 of the residual)
CONV_RESIDUAL_MINVAL= -9
%
% 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= o_fine_f30_m08.su2
%
% Mesh input file format (SU2, CGNS, NETCDF_ASCII)
MESH_FORMAT= SU2
%
% Mesh output file
%
% Restart flow input file
SOLUTION_FILENAME= restart_flow.dat
%
% Restart adjoint input file
SOLUTION_ADJ_FILENAME= solution_adj.dat
%
% Output file format (PARAVIEW, TECPLOT, STL)
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
%
% 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
%
% Output file surface adjoint coefficient (w/o extension)
SURFACE_ADJ_FILENAME= surface_adjoint
%
% Writing solution file frequency
OUTPUT_WRT_FREQ= 100
%
% Writing convergence history frequency
SCREEN_WRT_FREQ_INNER= 1
%
% Screen output fields
SCREEN_OUTPUT= (INNER_ITER, RMS_DENSITY, RMS_NU_TILDE, LIFT, DRAG, LINSOL_ITER, AVG_CFL )
VOLUME_OUTPUT= (COORDINATES, SOLUTION, PRIMITIVE, RESIDUAL)
HISTORY_OUTPUT= (INNER_ITER, RMS_DENSITY, DRAG, LIFT, NNER_ITER, RMS_DENSITY, RMS_MOMENTUM-X,RMS_MOMENTUM-Y, RMS_ENERGY)

[bigfootedrockmidget]

do you have a figure showing the results for the different mach numbers (with the comparison w. literature), together with a figure of the residual convergence?

[Batu]

Originally Posted by bigfootedrockmidget

do you have a figure showing the results for the different mach numbers (with the comparison w. literature), together with a figure of the residual convergence?

Sorry forgot to add them. I took the values from the graph because they did not give values as a table.

[bigfootedrockmidget]

Below is a comparison between the pressure coefficients from the Testcases configuration file (SST) and the experimental data from the nasa website (Ma=0.73)(https://www.grc.nasa.gov/WWW/wind/va...af/raetaf.html)
The difference in CL is less than 2%. So when your cases are all converged, then my best guess is that the testcase you are comparing to does not correspond to the testcase that you are simulating.

[bigfootedrockmidget]

BTW note that most RANS models cannot predict stall, so you will not be able to accurately predict the flow conditions for angles of attack higher than 6 degrees or so. I think stall happens at aoa=8-10 for the RAE 2822.

[Batu]

Originally Posted by bigfootedrockmidget

Below is a comparison between the pressure coefficients from the Testcases configuration file (SST) and the experimental data from the nasa website (Ma=0.73)(https://www.grc.nasa.gov/WWW/wind/va...af/raetaf.html)
The difference in CL is less than 2%. So when your cases are all converged, then my best guess is that the testcase you are comparing to does not correspond to the testcase that you are simulating.

But some cases correspond very similar. For example; Mach 0,9 and 1 at AoA 10 are very similar to reference. After these results, I thought my test cases were okay but after just changing the velocity couldn't catch references. Do I have to change more than velocity and Do u think that they were lucky results because as you mentioned it is a stall region and RANS don't work well?

[bigfootedrockmidget]

I think you should not draw any conclusions from a comparison of your results with numerical simulations that were 1. done with another code, 2. done with another turbulence model, 3. done without a grid convergence study, 4. done without verification with experiments.

For all we know, your results are correct and the paper of Kumar is wrong. I think it is better to (first) compare your setup with known measurements from the literature, like
https://www.grc.nasa.gov/www/wind/va...af/raetaf.html
https://www.sto.nato.int/publication...ARD-AR-138.pdf


Even if this validation is successful, it will be difficult to say anything about higher mach and higher angle of attack without an experiment to compare to.

[Batu]

Originally Posted by bigfootedrockmidget

I think you should not draw any conclusions from a comparison of your results with numerical simulations that were 1. done with another code, 2. done with another turbulence model, 3. done without a grid convergence study, 4. done without verification with experiments.

For all we know, your results are correct and the paper of Kumar is wrong. I think it is better to (first) compare your setup with known measurements from the literature, like
https://www.grc.nasa.gov/www/wind/va...af/raetaf.html
https://www.sto.nato.int/publication...ARD-AR-138.pdf


Even if this validation is successful, it will be difficult to say anything about higher mach and higher angle of attack without an experiment to compare to.

I already tried NASA results and they were okay. So gonna search other papers for reference. Thank you for your time.