Changes to solutionControl time consistency functions
I realised that we need separate treatment for transient and steady state solvers (which do not have ddt equation). Hence, I provided necessary interface and implementation for steady state solvers.
This commit is contained in:
Vuko Vukcevic
parent
edb77356aa
commit
ed03625c8b
3 changed files with 260 additions and 97 deletions
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@ -86,7 +86,7 @@ int main(int argc, char *argv[])
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U = rAU*HUEqn.H();
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// Consistently calculate flux
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piso.calcTimeConsistentFlux(phi, U, rAU, ddtUEqn);
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piso.calcTransientConsistentFlux(phi, U, rAU, ddtUEqn);
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adjustPhi(phi, U, p);
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@ -96,7 +96,7 @@ int main(int argc, char *argv[])
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(
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fvm::laplacian
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(
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rAU/piso.aCoeff(),
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fvc::interpolate(rAU)/piso.aCoeff(),
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p,
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"laplacian(rAU," + p.name() + ')'
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)
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@ -119,7 +119,7 @@ int main(int argc, char *argv[])
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# include "continuityErrs.H"
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// Consistently reconstruct velocity after pressure equation
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piso.reconstructVelocity(U, ddtUEqn, rAU, p, phi);
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piso.reconstructTransientVelocity(U, ddtUEqn, rAU, p, phi);
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}
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runTime.write();
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@ -238,6 +238,93 @@ const Foam::dimensionedScalar Foam::solutionControl::relaxFactor
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}
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void Foam::solutionControl::addDdtFluxContribution
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(
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surfaceScalarField& phi,
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surfaceScalarField& aCoeff,
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const surfaceVectorField& faceU,
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const volVectorField& U,
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const surfaceScalarField& rAUf,
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const fvVectorMatrix& ddtUEqn
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) const
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{
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// Add ddt scheme dependent flux contribution. Here: phi = H/A & Sf.
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phi += fvc::ddtConsistentPhiCorr(faceU, U, rAUf);
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// Add ddt scheme dependent contribution to diffusion scale coeff. Here:
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// aCoeff = 1.
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aCoeff += fvc::interpolate(ddtUEqn.A())*rAUf;
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}
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void Foam::solutionControl::addUnderRelaxationFluxContribution
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(
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surfaceScalarField& phi,
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surfaceScalarField& aCoeff,
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const volVectorField& U
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) const
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{
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// Get under-relaxation factor used in this iteration
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const dimensionedScalar alphaU(this->relaxFactor(U));
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const dimensionedScalar urfCoeff((1.0 - alphaU)/alphaU);
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// Add under-relaxation dependent flux contribution
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phi += urfCoeff*phi.prevIter();
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// Add under-relaxation dependent contribution to diffusion scale coeff
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aCoeff += urfCoeff*aCoeff;
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// Note: this is not 100% entirely consistent with the way FOAM handles
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// under-relaxation. In fvMatrix::relax() member function, the diagonal
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// dominance is first assured by limiting the diagonal and the matrix is
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// then relaxed. However, this is a very minor inconsistency, especially
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// since this term vanishes when non-linear iterations converge to a tight
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// tolerance (achieving steady state in SIMPLE or converging PISO/PIMPLE in
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// each time step). VV, 23/Dec/2016.
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}
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void Foam::solutionControl::correctBoundaryFlux
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(
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surfaceScalarField& phi,
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const volVectorField& U
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) const
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{
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// Get necessary data at the boundaries
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const volVectorField::GeometricBoundaryField& Ub = U.boundaryField();
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const surfaceVectorField::GeometricBoundaryField& Sb =
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mesh_.Sf().boundaryField();
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surfaceScalarField::GeometricBoundaryField& phib = phi.boundaryField();
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// Correct flux at boundaries depending on patch type. Note: it is possible
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// that we missed some important boundary conditions that need special
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// considerations when calculating the flux. Maybe we can reorganise this in
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// future by relying on distinction between = and == operators for
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// fvsPatchFields. However, that would require serious changes at the
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// moment. VV, 23/Dec/2016.
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forAll (phib, patchI)
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{
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if (Ub[patchI].fixesValue())
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{
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// This is fixed value patch, flux needs to be recalculated
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// with respect to the boundary condition
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phib[patchI] == (Ub[patchI] & Sb[patchI]);
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}
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else if
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(
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isA<slipFvPatchVectorField>(Ub[patchI])
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|| isA<symmetryFvPatchVectorField>(Ub[patchI])
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)
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{
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// This is slip or symmetry, flux needs to be zero
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phib[patchI] == 0.0;
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}
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}
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}
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// * * * * * * * * * * * * * * * * Constructors * * * * * * * * * * * * * * //
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Foam::solutionControl::solutionControl(fvMesh& mesh, const word& algorithmName)
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@ -273,7 +360,7 @@ Foam::solutionControl::~solutionControl()
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// * * * * * * * * * * * * * * * Member Functions * * * * * * * * * * * * * //
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void Foam::solutionControl::calcTimeConsistentFlux
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void Foam::solutionControl::calcTransientConsistentFlux
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(
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surfaceScalarField& phi,
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const volVectorField& U,
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@ -284,7 +371,7 @@ void Foam::solutionControl::calcTimeConsistentFlux
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// Store necessary fields for time consistency if they are not present
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if (!aCoeffPtr_ && !faceUPtr_)
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{
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aCoeffPtr_ = new volScalarField
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aCoeffPtr_ = new surfaceScalarField
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(
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IOobject
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(
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@ -316,20 +403,22 @@ void Foam::solutionControl::calcTimeConsistentFlux
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{
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FatalErrorIn
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(
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"tmp<surfaceScalarField> solutionControl::timeConsistentFlux"
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"void solutionControl::calcTransientConsistentFlux"
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"\n("
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"\n surfaceScalarField& phi,"
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"\n const volVectorField& U,"
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"\n const volScalarField& rAU"
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"\n const volScalarField& rAU,"
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"\n const fvVectorMatrix& ddtUEqn"
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"\n)"
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) << "Either aCoeffPtr_ or faceUPtr_ is allocated while the"
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<< " other is not. This must not happen."
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<< endl
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<< " other is not."
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<< nl
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<< " This must not happen in transient simulation. Make sure"
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<< " that functions aiding consistency are called in the right"
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<< " order (first flux and then velocity reconstruction)."
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<< exit(FatalError);
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}
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// Now that we are sure that pointers are valid and the fields are there, we
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// can do the calculation of the flux, while storing necessary data for
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// future velocity reconstruction.
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// Algorithm:
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// 1. Update flux and aCoeff due to ddt discretisation
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// 2. Update flux and aCoeff due to under-relaxation
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@ -337,11 +426,12 @@ void Foam::solutionControl::calcTimeConsistentFlux
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// remains consistent
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// Get fields that will be updated
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volScalarField& aCoeff = *aCoeffPtr_;
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surfaceScalarField& aCoeff = *aCoeffPtr_;
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surfaceVectorField& faceU = *faceUPtr_;
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// Update face interpolated velocity field. Note: handling of oldTime faceU
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// fields happens in ddt scheme when calling ddtConsistentPhiCorr
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// fields happens in ddt scheme when calling ddtConsistentPhiCorr inside
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// addDdtFluxContribution
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faceU = fvc::interpolate(U);
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// Interpolate original rAU on the faces
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@ -353,76 +443,90 @@ void Foam::solutionControl::calcTimeConsistentFlux
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// Calculate the ordinary part of the flux (H/A)
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phi = (faceU & mesh_.Sf());
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// Initialize aCoeff to 1
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aCoeff = dimensionedScalar("one", dimless, 1.0);
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// STAGE 1: consistent ddt discretisation handling
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// Add consistent flux contribution due to ddt discretisation
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phi += fvc::ddtConsistentPhiCorr(faceU, U, rAUf);
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// Calculate aCoeff according to ddt discretisation
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aCoeff = 1.0 + ddtUEqn.A()*rAU;
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addDdtFluxContribution(phi, aCoeff, faceU, U, rAUf, ddtUEqn);
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// STAGE 2: consistent under-relaxation handling
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// Get under-relaxation factor used in this iteration
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const dimensionedScalar alphaU = this->relaxFactor(U);
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// Helper variable
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const dimensionedScalar urfCoeff = (1.0 - alphaU)/alphaU;
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// Add consistent flux contribution due to possible under-relaxation
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phi += urfCoeff*fvc::interpolate(aCoeff)*phi.prevIter();
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// Add under-relaxation contribution to aCoeff
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aCoeff += urfCoeff*aCoeff;
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// Note: this is not 100% entirely consistent with the way FOAM handles
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// under-relaxation. In fvMatrix::relax() member function, the diagonal
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// dominance is first assured by limiting the diagonal and the matrix is
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// then relaxed. However, this is a very minor inconsistency, especially
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// since this term vanishes when non-linear iterations converge to a tight
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// tolerance (achieving steady state in SIMPLE or converging PISO/PIMPLE in
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// each time step). VV, 23/Dec/2016.
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addUnderRelaxationFluxContribution(phi, aCoeff, U);
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// STAGE 3: scale the flux and correct it at the boundaries
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// Scale the flux
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phi /= fvc::interpolate(aCoeff);
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// Get necessary data at the boundaries
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const volVectorField::GeometricBoundaryField& Ub = U.boundaryField();
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const surfaceVectorField::GeometricBoundaryField& Sb =
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mesh_.Sf().boundaryField();
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surfaceScalarField::GeometricBoundaryField& phib = phi.boundaryField();
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// Correct flux at boundaries depending on patch type. Note: it is possible
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// that we missed some important boundary conditions that need special
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// considerations when calculating the flux. Maybe we can reorganise this in
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// future by relying on distinction between = and == operators for
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// fvsPatchFields. However, that would require serious changes at the
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// moment. VV, 23/Dec/2016.
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forAll (phib, patchI)
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{
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if (Ub[patchI].fixesValue())
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{
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// This is fixed value patch, flux needs to be recalculated
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// with respect to the boundary condition
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phib[patchI] == (Ub[patchI] & Sb[patchI]);
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}
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else if
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(
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isA<slipFvPatchVectorField>(Ub[patchI])
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|| isA<symmetryFvPatchVectorField>(Ub[patchI])
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)
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{
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// This is slip or symmetry, flux needs to be zero
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phib[patchI] == 0.0;
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}
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}
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phi /= aCoeff;
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correctBoundaryFlux(phi, U);
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}
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void Foam::solutionControl::reconstructVelocity
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void Foam::solutionControl::calcSteadyConsistentFlux
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(
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surfaceScalarField& phi,
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const volVectorField& U
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) const
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{
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// Store aCoeff field for time consistency if it is not present. Note: faceU
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// does not need to be stored
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if (!aCoeffPtr_ && !faceUPtr_)
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{
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aCoeffPtr_ = new surfaceScalarField
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(
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IOobject
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(
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"aCoeff",
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mesh_.time().timeName(),
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mesh_,
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IOobject::NO_READ,
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IOobject::NO_WRITE
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),
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mesh_,
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dimensionedScalar("zero", dimless, 0.0)
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);
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}
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else if (faceUPtr_)
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{
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FatalErrorIn
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(
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"void solutionControl::calcSteadyConsistentFlux"
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"\n("
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"\n surfaceScalarField& phi,"
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"\n const volVectorField& U,"
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"\n const volScalarField& rAU"
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"\n)"
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) << "faceUPtr_ is allocated."
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<< nl
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<< " This must not happen in steady simulation. Make sure"
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<< " that the right functions aiding consistency are called in the"
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<< " right order (first flux and then velocity reconstruction)."
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<< exit(FatalError);
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}
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// Algorithm:
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// 1. Update flux and aCoeff due to under-relaxation
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// 2. Scale the flux with aCoeff, making sure that flux at fixed boundaries
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// remains consistent
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// Get aCoeff field
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surfaceScalarField& aCoeff = *aCoeffPtr_;
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// Store previous iteration for the correct handling of under-relaxation
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phi.storePrevIter();
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// Calculate the ordinary part of the flux (H/A)
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phi = (fvc::interpolate(U) & mesh_.Sf());
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// Initialize aCoeff to 1
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aCoeff = dimensionedScalar("one", dimless, 1.0);
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// STAGE 1: consistent under-relaxation handling
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addUnderRelaxationFluxContribution(phi, aCoeff, U);
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// STAGE 2: scale the flux and correct it at the boundaries
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phi /= aCoeff;
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correctBoundaryFlux(phi, U);
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}
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void Foam::solutionControl::reconstructTransientVelocity
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(
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volVectorField& U,
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const fvVectorMatrix& ddtUEqn,
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@ -444,15 +548,16 @@ void Foam::solutionControl::reconstructVelocity
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{
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FatalErrorIn
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(
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"void solutionControl::reconstructVelocity"
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"void solutionControl::reconstructTransientVelocity"
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"\n("
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"\n volVectorField& U,"
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"\n const volVectorField& ddtUEqn,"
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"\n const volScalarField& rAU,"
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"\n const volScalarField& p"
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"\n const surfaceScalarField& phi"
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"\n) const"
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) << "faceUPtr_ not calculated. Make sure you have called"
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<< " calculateTimeConsistentFlux(...) before calling this function."
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<< " calcTransientConsistentFlux(...) before calling this function."
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<< exit(FatalError);
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}
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surfaceVectorField& faceU = *faceUPtr_;
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@ -474,15 +579,31 @@ void Foam::solutionControl::reconstructVelocity
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}
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const Foam::volScalarField& Foam::solutionControl::aCoeff() const
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void Foam::solutionControl::reconstructSteadyVelocity
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(
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volVectorField& U,
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const volScalarField& rAU,
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const volScalarField& p
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) const
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{
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// Reconstruct the velocity field
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U -= rAU*fvc::grad(p);
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U.correctBoundaryConditions();
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// Note: no need to store and update faceU field for steady state run
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}
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const Foam::surfaceScalarField& Foam::solutionControl::aCoeff() const
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{
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if (!aCoeffPtr_)
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{
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FatalErrorIn
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(
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"const volScalarField& solutionControl::aCoeff() const"
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"const surfaceScalarField& solutionControl::aCoeff() const"
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) << "aCoeffPtr_ not calculated. Make sure you have called"
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<< " calculateTimeConsistentFlux(...) before calling aCoeff()."
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<< " calcTransientConsistentFlux(...) or "
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<< " calcSteadyConsistentFlux(...) before calling aCoeff()."
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<< exit(FatalError);
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}
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@ -145,7 +145,7 @@ protected:
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) const;
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// Time and under-relaxation consistency
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// Time and under-relaxation consistency helper functions
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//- Get relaxation factor for velocity field. Overriden in
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// pimpleControl since different relaxation factor may be used for
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@ -155,6 +155,34 @@ protected:
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const volVectorField& U
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) const;
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//- Add consistent flux contribution arising from time derivative
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// term. Note: aCoeff is parameter for clarity
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void addDdtFluxContribution
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(
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surfaceScalarField& phi,
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surfaceScalarField& aCoeff,
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const surfaceVectorField& faceU,
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const volVectorField& U,
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const surfaceScalarField& rAUf,
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const fvVectorMatrix& ddtUEqn
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) const;
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//- Add consistent flux contribution arising from the
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// under-relaxation. Note: aCoeff is parameter for clarity
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void addUnderRelaxationFluxContribution
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(
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surfaceScalarField& phi,
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surfaceScalarField& aCoeff,
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const volVectorField& U
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) const;
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//- Correct flux at the boundaries
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void correctBoundaryFlux
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(
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surfaceScalarField& phi,
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const volVectorField& U
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) const;
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private:
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@ -163,7 +191,7 @@ private:
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// Fields necessary for time and under-relaxation consistency
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//- A coeff (A^~) arising from consistency formulation
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mutable volScalarField* aCoeffPtr_;
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mutable surfaceScalarField* aCoeffPtr_;
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//- Face velocity needed for consistent formulation
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mutable surfaceVectorField* faceUPtr_;
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@ -230,16 +258,14 @@ public:
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inline bool consistent() const;
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// Time and under-relaxation consistency. Note: these functions could be
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// made virtual and specific to SIMPLE, PISO and PIMPLE, but we will
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// make them general in sense they account for arbitrary ddt scheme
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// and arbitrary under-relaxation (e.g. if someone runs SIMPLE in
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// transient mode or PISO with under-relaxation)
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// Time and under-relaxation consistency.
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// Note: argument matching U parameter needs to be equal U = H/A, where
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// H and A come from convection-difussion equation only (without time
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// derivative term)
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//- Calculate and return time consistent flux (before pressure
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// equation). At point of call, U = H/A where H and A come from
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// convection-diffusion equation only.
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void calcTimeConsistentFlux
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//- Calculate consistent flux for transient solvers (before pressure
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// equation).
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void calcTransientConsistentFlux
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(
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surfaceScalarField& phi,
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const volVectorField& U,
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|
|
@ -247,10 +273,17 @@ public:
|
|||
const fvVectorMatrix& ddtUEqn
|
||||
) const;
|
||||
|
||||
//- Reconstruct velocity (after pressure equation). At point of
|
||||
// call, U = H/A where H and A come from convection-diffusion
|
||||
// equation only
|
||||
void reconstructVelocity
|
||||
//- Calculate consistent flux for steady state solvers (before
|
||||
// pressure equation).
|
||||
void calcSteadyConsistentFlux
|
||||
(
|
||||
surfaceScalarField& phi,
|
||||
const volVectorField& U
|
||||
) const;
|
||||
|
||||
//- Reconstruct velocity for transient solvers (after pressure
|
||||
// equation and flux reconstruction).
|
||||
void reconstructTransientVelocity
|
||||
(
|
||||
volVectorField& U,
|
||||
const fvVectorMatrix& ddtUEqn,
|
||||
|
|
@ -259,8 +292,17 @@ public:
|
|||
const surfaceScalarField& phi
|
||||
) const;
|
||||
|
||||
//- Reconstruct velocity for steady state solvers (after pressure
|
||||
// equation and flux reconstruction).
|
||||
void reconstructSteadyVelocity
|
||||
(
|
||||
volVectorField& U,
|
||||
const volScalarField& rAU,
|
||||
const volScalarField& p
|
||||
) const;
|
||||
|
||||
//- Const access to aCoeff (needed for pressure equation)
|
||||
const volScalarField& aCoeff() const;
|
||||
const surfaceScalarField& aCoeff() const;
|
||||
|
||||
|
||||
// Evolution
|
||||
|
|
|
|||
Reference in a new issue