Can a deformed geometry/mesh be exported to GAMBIT?
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The user would like to export a deformed mesh/geometry from a free surface or FSI simulation so that it can be remeshed in GAMBIT. This is useful when mesh distortions are so high they are affecting the solution phase. This distortion can slow down convergence and may eventually cause the simulation to diverge due to mesh collapse. Though this situation is most like to arise in a transient simulation (large changes in the free surface shape leading to a distorted mesh after a certain number of time steps), it can also occur in steady state simulations where the mesh gets distorted after a certain number of iterations. The deformed geometry and the mesh can be exported using the FICONV module as follows: 1. Steady state: FICONV(NEUTRAL, OUTPUT, DEFORMED) OUTPUTFILE(FILE="iden.FDNEUT") 2. Unsteady (Transient) state: FICONV(NEUTRAL, OUTPUT, DEFORMED) RESULTFILE(FILE="iden.FDPOST", LAST=10) OUTPUTFILE(FILE="iden.FDNEUT") The above commands produce a neutral file, iden.FDNEUT, which contains information about the deformed mesh. No results are outputted to this file. Note, that this NEUTRAL FILE WILL OVERWRITE a pre-existing file (such as the one that Gambit exported) with the same name. In the transient case, the above commands will export the deformed mesh corresponding to time step 10. The deformed mesh can, then, be read into Gambit using the File -> Import -> Mesh option. You only need to specify the file name in the resulting form. In Gambit, you will notice that the edge labels may have changed from their defaults (edge.1, edge.2 etc). If the original neutral file contained a continuum entity called "fluid" comprising three faces (in 2-D) - face.1, face.2 and face.3 - then the geometry imported into Gambit will consist of only one face called "fluid" which is the union of the three faces. Thus, the geometry may need to be decomposed to obtain a good quality mesh. Also, the definitions of the boundary and continuum zones are lost during the import and they need to be redefined. |
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