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Coupling Code CoMA
CoMA (Coupling for Multiphysics Analysis) is a general code coupling tool, used in the simulation of surface coupled problems. It is developed since some years at the institute. The tasks of CoMA within a coupled analysis are:
- Control of the coupled computation and the single-field solvers
- Convergence control
- Coupling algorithms for implicit computations
- Data transfer between distributed interface meshes
- Communication between parallel single-field solvers and CoMA
This wiki should just give a short overview on how to use CoMA, being specific on FSI-simulation with Carat and OpenFOAM. Detailed information on programming concepts and theoretical aspects can be found in the dissertation of Thomas Gallinger.
Installation and Compilation
CoMA has to installed under Linux operating system, because FSI-jobs only run under Linux. There exists an svn-repository, which contains all CoMA sources. The svn-repository is hosted on the same server as the carat repository. The current IP is 129.187.141.99 and the folder is named "CoMA". Checkout the svn-repository. Open the file "makfile.in" in the src-directory. You have to adapt the variable "CoMA_DIR", which points to your CoMA installation path, and the variable "MPIHOME", pointing to your MPI installation path. Execute the shellscript "make_obj_directories" to set the directorires for the objety, and then type "make" to build CoMA software.
Problem Setup
The structure of the input file reflects the underlying programming concepts of CoMA. An example input file can be found in the svn-repository under the directory "example". The input file is block-structured. At least five different blocks have to specified:
- General
- Two Processgroups
- ExchangedQuantity
- Mapping
- Output
For an implicit FSI-simulation, three additional blocks have to be specified:
- ConvergenceCalculation
- Predictor
- CouplingAlgo
For a restart run, one block is necessary:
- Restart
Input File: Compulsory Block Description
| Block General: General control of application flow | ||
| Type | fsi or ffi or wind | defines MPI Ident tag of CoMA within MPI Environment, used by other codes to identify CoMA process |
|---|---|---|
| Method | implicit or explicit | implicit or explicit coupling, implicit with, explicit without inner iteration loops |
| Block Processgroup: Defines a group of processes, which belong to one field | ||
| ID | 0 or 1 | used to order processgroups and as reference for exchanged quantities |
|---|---|---|
| Name | string | for output only |
| InterfaceType | mpi or file | type of communication between CoMA and processgroup, Warning: type file only partly implemented |
| MPIIdentTag | 1 or 2 | used to identify processes of processgroup in MPI-universe |
| Block ExchangedQuantity: Defines a quantitiy to be exchanged between processgroups | ||
| ID | 0 or 1 or 2 ... | used to order quantities (0 exchanged before 1 before 2...) |
|---|---|---|
| Name | string | for output only |
| Dimension | int | dofs per node, e.g. displacements 3 |
| InterpolationType | 1 or 2 | 1 = flux mapping (summation e.g. for forces), 2 = field mapping (interpolation e.g. for displacements) |
| SenderID | int | ID of processgroups, which sends this quantitiy |
| RecieverID | int | ID of processgroups, which recieves this quantitiy |
| MpiTagBasis | int | used for MPI-data exchange of this quantitiy |
| DoFType | node | dummy paramter, quantitiy specified per node |
| Predictor - optional parameter | yes or no | use a predictor for this quantitiy in the first inner iteration and do not recieve from sender, block "Predictor" is necessary |
| CouplingAlgo - optional parameter | yes or no | use a coupling algorithm for this quantitiy, block "CouplingAlgo" is necessary |
| Convergence - optional parameter | yes or no | use a convergence criterion for this quantitiy, block "ConvergenceCalculation" is necessary |
| Block Mapping: Defines mapping method of exchanged quantities between surface meshes. | ||
| Type | TNM or MM | TNM: Triangular Nonmatching Mesh Mapper, MM: Matching Meshes |
|---|---|---|
| Block Output: General output of CoMA for postprocessing and simulation control | ||
| Path | string | absolute or relative path to directory for output files, created if necessary |
|---|---|---|
| Name | string | prefix for output file names |
| Format | gid or vtk | write ouput in Gid- or Vtk(Paraview)-format, Warning: Vtk writes out the mesh in every step, so huge data amount possible |
| Frequency | int | ouput ever int step |
| Energy | yes or no | additional output of energy |
| Convergence | yes or no | write additional file Path/Name+.cc with iteration information |
| QuantityID | int | which quantity to examine in .cc-file |
| Dof | yes or no | write dof-history in .cc-file, yes -> define node by following four entries: |
| ProcessgroupIndex | int | processgroup of dof |
| MeshTagIndex | int | meshTag of dof |
| NodeIndex | int | node index of dof |
| DofIndex | int | dof index of dof |
Input File: Optional Block Description
| Block Predictor: Defines a predictor for an exchanged Quantitiy used in the first inner itertation of a time step. | ||
| Type | polynomial or newmark or adaptive | Predictor type, for details see [1] |
|---|---|---|
| Order - for Type polynomial and newmark | int | polynomial: 0, 1, 2, 3; newmark: 1, 2; |
| Beta - for Type newmark | float | time integration parameter of Newmark scheme, standard: 0.25 |
| Gamma - for Type newmark | float | time integration parameter of Newmark scheme, standard: 0.50 |
| Block CouplingAlgo: Defines a coupling algorithm for an exchanged Quantitiy used in every inner itertation except the first of a time step. | ||
| Type | constant or aitken or quasinewton | Coupling algorithm type, for details see [1] |
|---|---|---|
| Factor - for Type constant, aitken and quasinewton | float | underrelaxation factor used always in constant relaxation, in the first iteration with Aitken and Quasi-Newton method |
| ConstRelax - for Type quasinewton | yes or no | use constant relaxation in first coupling iteration |
| NumHistoryDelta - for Type quasinewton | int | include delta information from preceeding timesteps into minimization problem |
| MinResChange - for Type quasinewton | float | dummy factor - not used |
| Block ConvergenceCalculation: Defines convergence properties for coupled computation. | ||
| By | CoMA or Processgroup | Which code performs convergence calculation |
|---|---|---|
| ProcessgroupID - for By processgroup | int | which group |
| Type - for By CoMA | absolute or relative | which convergence criterion should CoMA use, a absolute or relatve one |
| Limit - for By CoMA | float | convergence limit, if below=converged |
| CouplingSteps - for By CoMA | int | number of coupling steps (time steps) to be performed in total |
| MaxInnerLoopSteps - for By CoMA | int | number of maximum inner iteration loops |
| Block Restart: Used for computation with restart possibility | ||
| RestartRun | yes or no | Is this run a restart run |
|---|---|---|
| RestartFromStep - for RestartRun yes | int | from which step should the restart be performed |
| RestartOutput | yes or no | shoul restart-information be written ot output |
| RestartFrequency - for RestartOutput yes | int | write restart info every int step |
| RestartPath - for RestartOutput yes | string | absolute or relative path to directory for output, created if necessary |
| RestartFileName - for RestartOutput yes | string | prefix of restart info file names |
| RestartInfoInstances - for RestartOutput yes | int | instances of restart information in output files to be kept |
| PersistPredictorOrder - for RestartOutput yes | yes or no | write out all info necessary to preserve predictor order in restart |
References
- ↑ 1.0 1.1 Gallinger, T.G.: Effiziente Algorithmen zur partitionierten Lösung stark gekoppelter Probleme der Fluid-Struktur-Wechselwirkung, Dissertation, Lehrstuhl für Statik, Technische Universität München, 2010
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