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overset mesh boundary conditions leading to solution singularity

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Old   October 24, 2022, 13:37
Default overset mesh boundary conditions leading to solution singularity
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I am trying to run a simple test case with overset meshes. I have a flap inside a tube and I prescribe the motion of the flap. When I run the case with moveDynamicMesh, I get the required mesh motion. However, when I run the fluid solver, the solution always crashes within the first time step. It looks like I am doing something obviously wrong with the bc's but i'm not able to narrow it down. The outer tube is similar to a pipe bc with fixed inlet and zero pressure at the outlet. The overset patch has overset bc's and the flap has movingWallVelocity for U bc. Not sure if there is more to creating cellSets and the topoSet operations beyond what I've done. I have attached the sequence of steps through my run script here. Appreciate any pointers.


cd flap/
touch flap.foam    #
blockMesh    #creating the block around the flap; also the refinement zone or overset patch
snappyHexMesh -overwrite | tee log.shm_flap    #shm to create the wall patch
topoSet        #selecting every cell other than the "flap" patch
subsetMesh -overwrite c0 -patch flap    #not sure what this does - adding exposed internal cells to patch "flap"
transformPoints -scale '(0.5 0.5 0.5)' #to bring the flap to the centre (optional)
echo "completed meshing to flap part...moving to the background mesh"

cd ..

cd backGround/
touch backGround.foam
blockMesh    #background mesh
echo "completed meshing the background part...merging meshes"
mergeMeshes . ../flap -overwrite | tee log.mergeMeshes
topoSet | tee log.topoSet    #setting the cell sets c0 and c1
topoSet -dict ./system/topoSetDict_movingZone | tee log.movingZone    #creating a zone for dynamicMeshDict reader

rm -rf 0
cp -r 0_org 0

setFields -dict system/setFieldsDict_zoneID | tee log.setFields_zoneID    #0 for low priority; 1 for higher priority
transformPoints -scale '(0.001 0.001 0.001)'     #scaling the entire mesh to m
checkMesh |  tee log.checkMesh
cd ..
echo "completed the pre-processing steps..."


cd backGround/

#check the mesh movement by uncommenting the below line

overPimpleDyMFoam | tee log.solver
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movedynamicmesh, openfoam 2206, overpimpledymfoam, overset, singularity

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