# 2D Axisymmetric - symmetry axis in a supersonic external flow

 Register Blogs Members List Search Today's Posts Mark Forums Read April 30, 2020, 13:03 2D Axisymmetric - symmetry axis in a supersonic external flow #1 New Member   Imthiaz Syed Join Date: Nov 2019 Posts: 6 Rep Power: 3 Hello everyone, I have been running a 2D axisymmetric simulation of a flat plate (cylinder) at Mach 2.0. The mesh setup is very close to the NASA Flat Plate Validation Cases: https://turbmodels.larc.nasa.gov/flatplate.html.html except the entire mesh has been moved up in the y-axis by 0.125 (to signify a 125mm cylinder). In the above case, there is a symmetry condition near the inlet (shown in the figure in the link prior). I have read in forum posts before that SU2 treats the axis/edge given the boundary condition "MARKER_SYM" as the axis of rotation. Am I right in assuming that SU2 assumes the axis of symmetry is the x-axis if I use the exact same boundary conditions given in the link above? A follow-up question is what does SU2 do if I don't specify any MARKER_SYM boundary condition? Does the X=0 become the symmetry axis? I'm curious, because the simulation runs fine without specifying any symmetry axis. Thanks!   April 30, 2020, 14:22 #2 Member   Amit Join Date: May 2013 Posts: 85 Rep Power: 10 For axisymmetric simulation, you need to put AXISYMMETRIC=YES in your. cfg file. If you don't do this, MARKER_SYM will simply apply symmetry BC.   April 30, 2020, 16:20 #3 New Member   Imthiaz Syed Join Date: Nov 2019 Posts: 6 Rep Power: 3 Oh yes, ofcourse, I have set SOLVER= RANS and AXISYMMETRIC= YES. Even with the Axisymmetric option on, and setting MARKER_SYM= ( NONE ), SU2 runs fine. Does this mean it automatically assume x=0 is the symmetry axis?   April 30, 2020, 16:28 #4 New Member   Imthiaz Syed Join Date: Nov 2019 Posts: 6 Rep Power: 3 Here is the code im using. Essentially what I am trying to say is if i change Code: `MARKER_SYM= ( symmetry )` to Code: `MARKER_SYM= ( NONE )` and Code: `MARKER_EULER = ( NONE )` to Code: `MARKER_EULER = ( symmetry )` in the full code below, the asymmetric simulation runs fine. Code: ```%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % % SU2 configuration file % % Case description: Turbulent flow over flat plate with zero pressure gradient % % Author: Thomas D. Economon % % Institution: Stanford University % % Date: 2011.11.10 % % File Version 7.0.0 "Blackbird" % % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % ------------- DIRECT, ADJOINT, AND LINEARIZED PROBLEM DEFINITION ------------% % % Physical governing equations (EULER, NAVIER_STOKES, % WAVE_EQUATION, HEAT_EQUATION, FEM_ELASTICITY, % POISSON_EQUATION) SOLVER= RANS% Axisymmetric simulation, only compressible flows (NO, YES) AXISYMMETRIC= YES % % If Navier-Stokes, kind of turbulent model (NONE, SA) KIND_TURB_MODEL= SA % % Mathematical problem (DIRECT, CONTINUOUS_ADJOINT) MATH_PROBLEM= DIRECT % % Restart solution (NO, YES) RESTART_SOL= NO % % ----------- COMPRESSIBLE AND INCOMPRESSIBLE FREE-STREAM DEFINITION ----------% % % Mach number (non-dimensional, based on the free-stream values) MACH_NUMBER= 2.0 % % Angle of attack (degrees) AOA= 0.0 % % Side-slip angle (degrees) SIDESLIP_ANGLE= 0.0 % % Free-stream temperature (288.15 K by default) FREESTREAM_TEMPERATURE= 300.0 % % Reynolds number (non-dimensional, based on the free-stream values) REYNOLDS_NUMBER= 15000000.000 % % Reynolds length (in meters) REYNOLDS_LENGTH= 1.0 FREESTREAM_TURBULENCEINTENSITY = 0.004 FREESTREAM_TURB2LAMVISCRATIO = 0.009 % ---------------------- 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= 2.0 % -------------------- BOUNDARY CONDITION DEFINITION --------------------------% % % Navier-Stokes wall boundary marker(s) (NONE = no marker) MARKER_HEATFLUX= ( wall, 0.0 ) MARKER_ISOTHERMAL= ( wall, 513.6 ) % % Inlet boundary marker(s) (NONE = no marker) % Format: ( inlet marker, total temperature, total pressure, flow_direction_x, % flow_direction_y, flow_direction_z, ... ) %MARKER_INLET= ( inlet, 302.4, 118309.784, 1.0, 0.0, 0.0 ) MARKER_SUPERSONIC_INLET= (inlet, 300.0, 115056.0, 684.0, 0.0, 0.0) % % Outlet boundary marker(s) (NONE = no marker) % Format: ( outlet marker, back pressure, ... ) MARKER_OUTLET= (outlet, 115056.0, farfield, 115056.0) % % Symmetry boundary marker(s) (NONE = no marker) MARKER_SYM= ( symmetry ) % MARKER_EULER = ( NONE ) % % 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= ( inlet ) MARKER_ANALYZE = (inlet) MARKER_ANALYZE_AVERAGE = MASSFLUX WRT_SURFACE= YES % ------------- COMMON PARAMETERS DEFINING THE NUMERICAL METHOD ---------------% % % Numerical method for spatial gradients (GREEN_GAUSS, LEAST_SQUARES, % WEIGHTED_LEAST_SQUARES) NUM_METHOD_GRAD= GREEN_GAUSS % % Courant-Friedrichs-Lewy condition of the finest grid CFL_NUMBER= 0.5 % % 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, 0.1, 20.0 ) % % Runge-Kutta alpha coefficients RK_ALPHA_COEFF= ( 0.66667, 0.66667, 1.000000 ) % % Number of total iterations ITER= 99999999 % ----------------------- 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 -----------------------------% % % Multi-Grid Levels (0 = no multi-grid) MGLEVEL= 0 % % Multi-grid cycle (V_CYCLE, W_CYCLE, FULLMG_CYCLE) MGCYCLE= V_CYCLE % % Multi-grid pre-smoothing level MG_PRE_SMOOTH= ( 1, 2, 3, 3 ) % % Multi-grid post-smoothing level MG_POST_SMOOTH= ( 2, 2, 2, 2) % % 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, 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 (NONE, VENKATAKRISHNAN, VENKATAKRISHNAN_WANG, % BARTH_JESPERSEN, VAN_ALBADA_EDGE) SLOPE_LIMITER_FLOW= NONE % % 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 % % Slope limiter (VENKATAKRISHNAN, MINMOD) SLOPE_LIMITER_TURB= VENKATAKRISHNAN % % Time discretization (EULER_IMPLICIT) TIME_DISCRE_TURB= EULER_IMPLICIT % --------------------------- CONVERGENCE PARAMETERS --------------------------% % % Convergence criteria (CAUCHY, RESIDUAL) CONV_CRITERIA= RESIDUAL % % % Min value of the residual (log10 of the residual) CONV_RESIDUAL_MINVAL= -15 % % Start convergence criteria at iteration number CONV_STARTITER= 15 % % 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= med_axi_0125mm.su2 % % Mesh input file format (SU2, CGNS, NETCDF_ASCII) MESH_FORMAT= SU2 % % Mesh output file MESH_OUT_FILENAME= mesh_out.su2 % % Restart flow input file SOLUTION_FILENAME= solution_flow.dat % % Restart adjoint input file SOLUTION_ADJ_FILENAME= solution_adj.dat % % Output file format (PARAVIEW, TECPLOT, SLT) TABULAR_FORMAT= TECPLOT % % 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 WRT_SOL_FREQ= 1000 % % Writing convergence history frequency WRT_CON_FREQ= 10 % % Screen output fields SCREEN_OUTPUT= (INNER_ITER, RMS_DENSITY, RMS_MOMENTUM-X, RMS_MOMENTUM-Y, AVG_MASSFLOW) SCREEN_WRT_FREQ_INNER= 1 % SCREEN_WRT_FREQ_OUTER= 1 % SCREEN_WRT_FREQ_TIME= 1 OUTPUT_FILES= (RESTART, PARAVIEW, SURFACE_PARAVIEW)```   April 30, 2020, 18:56 #5 Member   Amit Join Date: May 2013 Posts: 85 Rep Power: 10 Not sure about it. If you don't specify a boundary condition (or to say proper boundary condition), problem becomes ill posed (even though you may get some solution). What default boundary condition it is falling to if you don't specify it, I am not sure. Some body from community may comment.  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