Closed veiguf closed 6 years ago
Hi, The skyline linear solver is likely very slow for such a large mesh. I would suggest switching to the _complex_pastixsolver. This is an external solver so you first need to install pastix and enable it in the ExternalSolversApplication. The following may be helpful
https://github.com/KratosMultiphysics/Kratos/wiki/How-to-use-the-PaStiX-solver-in-Kratos
Thank you for your suggestion! I installed pastix and recompiled kratos. I tested it on the example I have uploaded above. Below you can find the new solver settings. The computation time is about the same as it was with the other linear solver. Did I do something wrong? Are there other possibilities?
"eigensolver_settings":{
"solver_type": "FEAST",
"print_feast_output": true,
"perform_stochastic_estimate": false,
"solve_eigenvalue_problem": true,
"lambda_min": 1e7,
"lambda_max": 2e7,
"search_dimension": 40,
"linear_solver_settings":{
"solver_type": "complex_pastix_solver"
}
},
You could also have a look at the EigenSolversApplication. It offers an alternative solver for eigenvalue problems. In combination with the MKL library it should be quite fast. (At a first step you can also try without MKL) Have a look at https://github.com/KratosMultiphysics/Kratos/tree/master/applications/EigenSolversApplication
Hi @armingeiser! I installed the EigenSolversApplication as you mentioned for now without MKL. With a low number of eigenvalues the simulation runs quite fast. But the results I get are very strange to me. The eigenvalues are around zero and the mode shapes look strange. Could you please check if I defined the parameters correctly? Test2.zip
"solver_settings" : {
"solver_type" : "eigen_value",
"echo_level" : 1,
"scheme_type" : "dynamic",
"model_import_settings" : {
"input_type" : "mdpa",
"input_filename" : "Test"
},
"material_import_settings" : {
"materials_filename" : "StructuralMaterials.json"
},
"eigensolver_settings":{
"solver_type": "eigen_eigensystem",
"number_of_eigenvalues": 2,
"max_iteration": 1000,
"tolerance": 1e-6,
"echo_level": 1
},
"line_search" : false,
"convergence_criterion" : "residual_criterion",
"displacement_relative_tolerance" : 100,
"displacement_absolute_tolerance" : 1e-3,
"residual_relative_tolerance" : 100,
"residual_absolute_tolerance" : 1e-3,
"max_iteration" : 10,
"problem_domain_sub_model_part_list" : ["Parts_Body"],
"processes_sub_model_part_list" : [],
"rotation_dofs" : false
},
The problem seems to be that the structure is not supported. If you add supports it should work.
Thank you! You are right, with boundary conditions it works well! But I would like to compute also the eigenfrequencies of unsupported structures. The first 6 eigenvalues of an unsupported structure should be ca. 0 which corresponds to the free-body movement. Is this not possible with this solver?
Unfortunately I have no experience with the eigenfrequencies of unsupported structures...
Can we close this?
I am a student at the Free University of Bozen-Bolzano, currently working on a study project using Kratos Multiphysics. I am using the FEAST SOLVER to calculate the mode shapes and eigenfrequencies of different components. I have noticed that the calculation time becomes very long increasing the degrees of freedom. At the moment I’m trying to get results for a 3D mesh with 34000 nodes and 172000 tetrahedral elements and the simulation takes many hours and giving at the end an error message. I understood that the search dimension should be increased but I would like to avoid to wait so long for the next simulation. Attached you can find a 3D beam which I created for test reasons. The simulation takes about 5 minutes which also seems to be long for that simple structure. Test.zip Are there some parameters which can be changed in order to decrease the computation time? What else could I change? Any help would be appreciated!