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October 17, 2005, 04:54 |
Can any one explain a little a
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#1 |
Senior Member
Maka Mohu
Join Date: Mar 2009
Posts: 305
Rep Power: 18 |
Can any one explain a little about how to set pRefCell and pRefValue in fvSolution dictionary since they have been introduced in 1.2.
I changed the mesh for channelOodles and I got a warning message about pRefCell. Thanks. PISO { nCorrectors 2; nNonOrthogonalCorrectors 0; pRefCell 1001; pRefValue 0; } Regards, Maka. |
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October 18, 2005, 11:10 |
If you have an incompressible
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#2 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,905
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If you have an incompressible flow in a domain where none of the boundaries uses a fixed value (or similar) boundary condition, the value of the pressure in the system is indeterminate to a constant. Iterative solvers dont like that because the solution can jump and down, so we need to do tricks to make sure it does not happen.
The way to do this is to specify the pressure level in one cell. Previously, this used to be cell zero with value zero and hard-coded in the solver, but this causes trouble when the cell is next to a coupled boundary. The new entries allow you to control in which cell the pressure is given and to which level. Hrv
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April 30, 2009, 15:44 |
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#3 |
New Member
Suraj Deshpande
Join Date: Mar 2009
Location: Madison, WI, USA
Posts: 18
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Hello,
What is done with pdRefCell and pdRefValue when atleast one of the boundaries has a a fixed value of pressure specified? Is pdRefValue still used then? Thanks, Suraj |
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October 15, 2014, 05:19 |
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#4 |
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Nicole Andrew
Join Date: Sep 2014
Location: Pretoria, South Africa
Posts: 58
Rep Power: 11 |
Hi Suraj,
I see this is a very old post, but did you ever find an answer to your question bout the fixed boundary pressure? Thanks, Nicole |
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October 22, 2014, 14:17 |
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#5 | |
Senior Member
ArathoN
Join Date: Jul 2011
Posts: 137
Rep Power: 15 |
Quote:
from createFields.H Code:
label pRefCell = 0; scalar pRefValue = 0.0; setRefCell(p, mesh.solutionDict().subDict("PIMPLE"), pRefCell, pRefValue); Code:
fvScalarMatrix pEqn ( fvm::laplacian(rAUf, p) == fvc::div(phiHbyA) ); pEqn.setReference(pRefCell, pRefValue); pEqn.solve(mesh.solver(p.select(pimple.finalInnerIter()))); IMO if there is no declaration of pRefCell or pRefValue in pimple they will not created by createFields.H Code:
setRefCell(p, mesh.solutionDict().subDict("PIMPLE"), pRefCell, pRefValue); EDIT: at fvCFD.H included in pimplefoam you'll find the findRefCell.C where it is defined the serRefCell function: Code:
if (fieldRef.needReference() || forceReference) {................} EDIT2: I've found it, the function "needReference" is defined GeometricField.C as such: Code:
bool Foam::GeometricField<Type, PatchField, GeoMesh>::needReference() const { // Search all boundary conditions, if any are // fixed-value or mixed (Robin) do not set reference level for solution. bool needRef = true; forAll(boundaryField_, patchi) { if (boundaryField_[patchi].fixesValue()) { needRef = false; break; } } reduce(needRef, andOp<bool>()); return needRef; } |
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February 17, 2015, 03:00 |
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#6 |
Member
Nicole Andrew
Join Date: Sep 2014
Location: Pretoria, South Africa
Posts: 58
Rep Power: 11 |
Thank you so much for your well-explained response. Sorry for only replying now, but we did find your response very useful!
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