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Old   December 27, 2023, 11:12
Default Transferring Total Fluid stress of FS-Interface
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Hello Foamers,

I want to Total Fluid viscous (isotropic or hydro stress [-p*I] and anisotropic or deviatoric stress [sigmaFluid = 2*nuf*dev(symm(fvc::grad(U)))] on the Fluid-Solid Interface patches.

I am not sure how to code the face normals and transfer the total fluid stress on the interfaces to account for the dynamic condition at FS-Interface.

Fluid-Solid interface patches :

patch consoleFluid (in Blue)
( (7 6 2 3) (0 1 5 4) )
patch outlet
( (1 5 6 2) )

patch consoleSolid (in Red)
( (8 9 21 20) (23 22 10 11) )
patch midNotch
( (9 10 22 21) )

So, here are my questions:

1. Since i will have 3 face normals ( 2 face normals from patch consoleFluid/consoleSolid) and one face normal (oulet/midNotch), I have tried to proceed as below but having some errors.

// Solid Domain
label consoleSolidPatchID = stressMesh.boundaryMesh().findPatchID("consoleSoli d");
label midNotchPatchID = stressMesh.boundaryMesh().findPatchID("midNotch");

// Fluid Domain
label consoleFluidPatchID = mesh.boundaryMesh().findPatchID("consoleFluid");
label outletPatchID = mesh.boundaryMesh().findPatchID("outlet");

vectorField faceNormal1 = (stressMesh.Sf().boundaryField()[consoleSolidPatchID])

vectorField faceNormal2 = (stressMesh.Sf().boundaryField()[midNotchPatchID])

symmTensorField solidPatchTraction1 =

symmTensorField solidPatchTraction2 =

solidPatchTraction1 *= rho.value();
solidPatchTraction2 *= rho.value();

tForce.traction() = (solidPatchTraction1 & faceNorma11) + (solidPatchTraction2 & faceNormal2);

My code crashes at this point with the following error :

given field does not correspond to patch. Patch size: 20 field size: 10

From function PatchToPatchInterpolation::faceInterpolate(const Field<Type> ff)
in file /home/user/foam/foam-extend-5.0/src/foam/lnInclude/PatchToPatchInterpolate.C at line 128.

Please how can I code to match the face normals to the patches so as to have the traction force on the patches right.

b. Can I do this for the traction vector calculation?

vectorField tractionVector1 =
(sigmaFluid.boundaryField()[consoleFluidPatchID] & faceNormal1)

vectorField tractionVector2 =
(sigmaFluid.boundaryField()[outletPatchID] & faceNormal2)

vector totalTractionForce =
+ tractionVector2*rho.value()

Info << "Total traction force = " << totalTractionForce << endl;

c. Please, where does the totalTractionForce is used in the solver? Because I canít figure out. Is it in the tractionDisplacement BC code? If yes, how? Because I canít see the linkage...

d. Finally, when we have the code below:
scalarField solidPatchPressure =

solidPatchPressure *= rhoFluid.value();

tForce.pressure() = solidPatchPressure;

vector totalPressureForce =
Info << "Total pressure force = " << totalPressureForce << endl;

where does the totalPressureForce is used in the solver? Because I canít figure out. Is it in the tractionDisplacement BC code? If yes, how? Because I canít see the linkage...

Thank You.
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