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May 26, 2023, 11:47 
su2 nemo divergence hypersonic apollo

#1 
New Member
Nicola Trippella
Join Date: May 2023
Location: Milan
Posts: 15
Rep Power: 2 
Hi
I am trying for many days to make a simulation for a reentry bluff body, an Apollo like capsule, at hypersonic velocity. My intial goal was to study it at h = 38 km, Mach = 5, with air5 model for air, p and T found in internet for 38 km altitude. However, simulation was not converging. So i decided to consider at first a subsonic mach, Mach = 0.5, at the same altitude of 38 km. HOwvwer, still the simulation is not converging. I am wondering many questions:  why the simulation starts only with AUSM scheme? WHen i try to use ASUM+UP or AUSM+M , the simulation does not make any iteration, displaying "SU2 has diverged" what is my possible error? I have done so many tentatives. There is an error on the mesh? My mesh is a fully unstrcutred one, with smaller elements near the capsule. Myabe, i am putting something worng inside the config? Here, below, i will copy the config and the mesh.geo texts I will attach some images about: mesh and results of the simulation. This is the config:  SOLVER= NEMO_EULER MATH_PROBLEM= DIRECT RESTART_SOL= NO READ_BINARY_RESTART= NO TIME_DOMAIN= NO % FROZEN_MIXTURE=NO TRANSPORT_COEFF_MODEL = CHAPMANNENSKOG KIND_TURB_MODEL= NONE % FLUID_MODEL= MUTATIONPP GAS_MODEL= air_5 GAS_COMPOSITION= (0.0, 0.0, 0.00, 0.79, 0.21) % % Reference origin for moment computation : CG coordinates REF_ORIGIN_MOMENT_X = 1.1455 REF_ORIGIN_MOMENT_Y = 0.1600 REF_ORIGIN_MOMENT_Z = 0.00 % % Reference length for pitching, rolling, and yawing nondimensional moment REF_LENGTH= 3.9116 % % Reference area for force coefficients (0 implies automatic calculation) REF_AREA= 12.020 % INIT_OPTION= TD_CONDITIONS MACH_NUMBER= 0.5 AOA= 0.0 FREESTREAM_PRESSURE= 377.1 FREESTREAM_TEMPERATURE= 244.8 FREESTREAM_TEMPERATURE_VE= 244.8 % MARKER_FAR = ( FARFIELD ) MARKER_EULER = ( CAPSULE ) % MARKER_PLOTTING= ( CAPSULE ) MARKER_MONITORING= ( CAPSULE ) % ITER= 1000000 NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES CFL_NUMBER= 0.05 % CFL_ADAPT= YES % CFL_ADAPT_PARAM= (0.0005, 1.0005, 0, 1) RK_ALPHA_COEFF= ( 0.66667, 0.66667, 1.000000 ) LINEAR_SOLVER= BCGSTAB LINEAR_SOLVER_ERROR= 1E6 LINEAR_SOLVER_ITER= 5 % CONV_NUM_METHOD_FLOW= AUSM MUSCL_FLOW= NO SLOPE_LIMITER_FLOW= VENKATAKRISHNAN_WANG VENKAT_LIMITER_COEFF= 0.01 TIME_DISCRE_FLOW= EULER_EXPLICIT % % Min value of the residual (log10 of the residual) CONV_RESIDUAL_MINVAL= 50 % MESH_FILENAME= apoll.su2 MESH_FORMAT= SU2 TABULAR_FORMAT= CSV SOLUTION_FILENAME= restart_flow5_nemo.dat %OUTPUT_FILES= (RESTART_ASCII, PARAVIEW, SURFACE_PARAVIEW) CONV_FILENAME= history5_nemo RESTART_FILENAME= restart_flow5_nemo VOLUME_FILENAME= soln_volume5_nemo SURFACE_FILENAME= soln_surface5_nemo OUTPUT_WRT_FREQ= 1000 SCREEN_WRT_FREQ_TIME= 100 SCREEN_WRT_FREQ_OUTER= 100 SCREEN_OUTPUT= (INNER_ITER, RMS_DENSITY_4, RMS_DENSITY_5, RMS_ENERGY, RMS_ENERGY_VE, DRAG, CAUCHY_DRAG) VOLUME_OUTPUT= (COORDINATES, SOLUTION, PRIMITIVE, AUXILIARY, RESIDUAL) HISTORY_OUTPUT= (ITER, RMS_RES, CFL_NUMBER)  This is my geo file:  H = 0.75; h = 0.0075; R = 80; //CAPSULE Point(1) = {0.3743, 1.8368, 0, h}; //+ Point(2) = {0.3743, 1.8368, 0, h}; //+ Point(3) = {0.5543, 1.9558, 0, h}; //+ Point(4) = {0.5543, 1.9558, 0, h}; //+ Point(5) = {3.3254, 0.1938, 0, h}; //+ Point(6) = {3.3254, 0.1938, 0, h}; //+ Point(7) = {3.4306, 0, 0, h}; //+ Point(8) = {0.554227, 1.760289, 0, h}; //+ Point(9) = {0.554227, 1.760289, 0, h}; //+ Point(10) = {3.1995, 0, 0, h}; //+ Point(11) = {4.6939, 0, 0, h}; //+ Point(12) = {0.6608, 1.9242, 0, h}; //+ Point(13) = {0.6608, 1.9242, 0, h}; //+ //+ Circle(1) = {1, 8, 12}; //+ Circle(2) = {2, 9, 13}; //+ Circle(3) = {5, 10, 6}; //+ Circle(4) = {1, 11, 2}; //+ Line(5) = {12, 5}; //+ Line(6) = {6, 13}; //FARFIELD Point(15) = {R+30, 0, 0, H}; Point(16) = {30, R, 0, H}; Point(17) = {R+30, 0, 0, H}; Point(18) = {30, R, 0, H}; // farfield center Point(19) = {30,0,0,H}; Circle(7) = {15, 19, 16}; Circle(8) = {16, 19, 17}; Circle(9) = {17, 19, 18}; Circle(10) = {18, 19, 15}; Physical Curve("CAPSULE", 1) = {5, 1, 4, 2, 6, 3}; //+ Physical Curve("FARFIELD", 2) = {7, 8, 9, 10}; Curve Loop(1) = {8, 9, 10, 7}; //+ Curve Loop(2) = {1, 5, 3, 6, 2, 4}; //+ Plane Surface(1) = {1, 2}; //+ Physical Surface("VOLUME", 1) = {1};  

May 31, 2023, 03:45 

#2 
Member
Giovanni Medici
Join Date: Mar 2014
Posts: 44
Rep Power: 11 
Possibly I'm getting it wrong (and there may be other details to correct) but in your solution and in your cfg it is simulating Mach 0.5 and not 5.0.
I'd revise the cfg and retry. 

June 2, 2023, 04:23 
1sto order ok, second no

#3 
New Member
Nicola Trippella
Join Date: May 2023
Location: Milan
Posts: 15
Rep Power: 2 
Hi
Thanks for your interest, Giovanni. Sorry for the late repsonse. My initially intention was to make convergence for a subsonic case, like M = 0.5. Anyway, i managed to reach convergence for M = 5. 1) the mesh is an unstrctured one, refined gradually near the capsule. I made 2 concentric circles around the capsule in order to impose in these 'construction' lines a desired mesh dimension so that from the farfield to the capsule the sizes are less and less. Moreover, i reduced the extranl domain radius from 80 to 50 since the computational effort with 80 was to high, so that i could not see convergence even attending 4/5 hours. 2) in the config file i put M = 5 and these are the main options: SOLVER= NEMO_EULER MATH_PROBLEM= DIRECT RESTART_SOL= NO READ_BINARY_RESTART= NO TIME_DOMAIN= NO FROZEN_MIXTURE=NO TRANSPORT_COEFF_MODEL = CHAPMANNENSKOG KIND_TURB_MODEL= NONE FLUID_MODEL= MUTATIONPP GAS_MODEL= air_5 %N O NO N2 O2 GAS_COMPOSITION= (0.0, 0.0, 0.00, 0.79, 0.21) REF_ORIGIN_MOMENT_X = 1.1455 REF_ORIGIN_MOMENT_Y = 0.1600 REF_ORIGIN_MOMENT_Z = 0.00 REF_LENGTH= 3.9116 REF_AREA= 12.020 INIT_OPTION= TD_CONDITIONS MACH_NUMBER= 5 AOA= 0.0 FREESTREAM_PRESSURE= 377.1 FREESTREAM_TEMPERATURE= 244.8 FREESTREAM_TEMPERATURE_VE= 244.8 MARKER_FAR = ( FARFIELD ) MARKER_EULER = ( CAPSULE ) %%% MARKER_PLOTTING= ( CAPSULE ) MARKER_MONITORING= ( CAPSULE ) ITER= 120000 NUM_METHOD_GRAD= WEIGHTED_LEAST_SQUARES CFL_NUMBER= 0.25 CFL_ADAPT= YES CFL_ADAPT_PARAM= (0.005, 1.005, 0.1, 1) RK_ALPHA_COEFF= ( 0.66667, 0.66667, 1.000000 ) LINEAR_SOLVER= BCGSTAB LINEAR_SOLVER_ERROR= 1E6 LINEAR_SOLVER_ITER= 5 CONV_NUM_METHOD_FLOW= AUSM MUSCL_FLOW= NO SLOPE_LIMITER_FLOW= VENKATAKRISHNAN_WANG VENKAT_LIMITER_COEFF= 0.01 TIME_DISCRE_FLOW= EULER_EXPLICIT CONV_RESIDUAL_MINVAL= 50 Now my new next challenge will be to reach convergence for a second order scheme, with MUSCL active. I tried just restarting from the first order, putting MUSCL = YES, limiter = VENKATAKRISHNAN_WANG and AUSM scheme. However, residuals oscillate for 2/3 hours around +3 I don't know what i could do, since when for example i try to change my numerical scheme in AUSM+M, the simulation does not even starts. Maybe i have to refine mesh so that AUSM+M could start? Any other suggestion? 

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ausm, divergence, hypersonic, nemo, su2 
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