dynamic mesh control

H. AKIMOTO, Division of Ocean Systems Engineering (OSE), Korea Advanced Institute of Science and Technology

Dynamic mesh controlDynamic mesh controlDynamic mesh controlDynamic mesh control

• Dynamic mesh control• Deformation• Rotational motion

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Dynamic mesh related problems

• Motion of object in fluid▫ Body motion with boundaries (wall, ground, free

surface) requires dynamic mesh(alternative solution is overset mesh)

Note: If all the outer boundaries are open, deformation is not needed

• Rotating machine (open test)▫ Moving Reference of Frame (MRF)

• Rotating machine with casing▫ Sliding mesh technique

2


pimpleDyMFoam solver

• movingCone case▫ Mesh: solution of Laplacian solver

• Needs velocity boundary condition of mesh

• wingMotion case▫ snappyHexMesh : meshing▫ simpleFoam : prepare steady flow field▫ pimpleDyMFoam : flow simulation with motion

3


OpenFOAM cases of dynamic mesh

• MRF example▫ incompressible/MRFSimpleFoam/mixerVessel2DStatic mesh in rotating coordinates

• Dynamic mesh example▫ incompressible/pimpleDyMFoam

• movingCone : Defomation of mesh• mixerVesselAMI2D : • wingMotion

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Arbitrary Mesh Interface (AMI)AMI is for• un-matched/non-conformal cyclic

patch pairs• sliding interfaces, e.g. for rotating

machinery• mapped patches, e.g. for coupling• simulations between separate

mesh regions, such as surface film and bulk flow.

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Rotating turbine example

• Prepare “Fluent case files” of rotating part and stationery part separatelyInner.cas and outer.cas

• Convert the Fluent case files to OpenFOAMcase directory▫ fluentMeshToFoam –writeZone –writeSets

inner.cas▫ fluentMeshToFoam –writeZone –writeSets

outer.cas

Point is providing “two cases”6


• Merge two meshes▫ $ mergeMesh inner outer

It creates merged mesh in run/inner/1e-5 (something like that)

Directory name is the "first time step" determined by controlDict

• Create rotating simulation case▫ Prepare mycase/system and mycase/constant▫ Copy inner/1e-5/polymesh to the new case

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• Create cellZone data in the new case▫ splitMeshRegions -makeCellZones –overwrite

• Edit constant/polymesh/boundary and set AMI patches

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inner-AMI{

type cyclicAMI;nFaces 16;startFace 304;matchTolerance 0.0001;neighbourPatch outer-AMI;transform noOrdering;

}

outer-AMI{

type cyclicAMI;nFaces 16;startFace 320;matchTolerance 0.0001;neighbourPatch inner-AMI;transform noOrdering;

}

Then edit boundary condition and run the simulation

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dynamic mesh control

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