243 lines
6.9 KiB
C++
243 lines
6.9 KiB
C++
if (ign.ignited())
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{
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// progress variable
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// ~~~~~~~~~~~~~~~~~
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volScalarField c = scalar(1) - b;
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// Unburnt gas density
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// ~~~~~~~~~~~~~~~~~~~
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volScalarField rhou = thermo.rhou();
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// Calculate flame normal etc.
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~
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volVectorField n = fvc::grad(b);
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volScalarField mgb = mag(n);
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dimensionedScalar dMgb = 1.0e-3*
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(b*c*mgb)().weightedAverage(mesh.V())
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/((b*c)().weightedAverage(mesh.V()) + SMALL)
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+ dimensionedScalar("ddMgb", mgb.dimensions(), SMALL);
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mgb += dMgb;
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surfaceVectorField SfHat = mesh.Sf()/mesh.magSf();
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surfaceVectorField nfVec = fvc::interpolate(n);
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nfVec += SfHat*(fvc::snGrad(b) - (SfHat & nfVec));
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nfVec /= (mag(nfVec) + dMgb);
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surfaceScalarField nf = (mesh.Sf() & nfVec);
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n /= mgb;
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# include "StCorr.H"
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// Calculate turbulent flame speed flux
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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surfaceScalarField phiSt = fvc::interpolate(rhou*StCorr*Su*Xi)*nf;
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scalar StCoNum = max
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(
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mesh.surfaceInterpolation::deltaCoeffs()
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*mag(phiSt)/(fvc::interpolate(rho)*mesh.magSf())
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).value()*runTime.deltaT().value();
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Info<< "Max St-Courant Number = " << StCoNum << endl;
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// Create b equation
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// ~~~~~~~~~~~~~~~~~
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fvScalarMatrix bEqn
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(
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fvm::ddt(rho, b)
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+ mvConvection->fvmDiv(phi, b)
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+ fvm::div(phiSt, b, "div(phiSt,b)")
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+ fvm::SuSp(-fvc::div(phiSt), b)
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- fvm::laplacian(turbulence->alphaEff(), b)
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);
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// Add ignition cell contribution to b-equation
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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# include "ignite.H"
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// Solve for b
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// ~~~~~~~~~~~
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bEqn.solve();
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Info<< "min(b) = " << min(b).value()
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<< " max(b) = " << max(b).value() << endl;
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// Calculate coefficients for Gulder's flame speed correlation
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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volScalarField up = uPrimeCoef*sqrt((2.0/3.0)*turbulence->k());
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//volScalarField up = sqrt(mag(diag(n * n) & diag(turbulence->r())));
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volScalarField epsilon = pow(uPrimeCoef, 3)*turbulence->epsilon();
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volScalarField tauEta = sqrt(thermo.muu()/(rhou*epsilon));
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volScalarField Reta = up/
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(
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sqrt(epsilon*tauEta) + dimensionedScalar("1e-8", up.dimensions(), 1e-8)
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);
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//volScalarField l = 0.337*k*sqrt(k)/epsilon;
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//Reta *= max((l - dimensionedScalar("dl", dimLength, 1.5e-3))/l, 0.0);
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// Calculate Xi flux
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// ~~~~~~~~~~~~~~~~~
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surfaceScalarField phiXi =
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phiSt
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- fvc::interpolate(fvc::laplacian(turbulence->alphaEff(), b)/mgb)*nf
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+ fvc::interpolate(rho)*fvc::interpolate(Su*(1.0/Xi - Xi))*nf;
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// Calculate mean and turbulent strain rates
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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volVectorField Ut = U + Su*Xi*n;
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volScalarField sigmat = (n & n)*fvc::div(Ut) - (n & fvc::grad(Ut) & n);
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volScalarField sigmas =
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((n & n)*fvc::div(U) - (n & fvc::grad(U) & n))/Xi
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+ (
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(n & n)*fvc::div(Su*n)
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- (n & fvc::grad(Su*n) & n)
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)*(Xi + scalar(1))/(2*Xi);
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// Calculate the unstrained laminar flame speed
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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volScalarField Su0 = unstrainedLaminarFlameSpeed()();
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// Calculate the laminar flame speed in equilibrium with the applied strain
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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volScalarField SuInf = Su0*max(scalar(1) - sigmas/sigmaExt, scalar(0.01));
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if (SuModel == "unstrained")
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{
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Su == Su0;
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}
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else if (SuModel == "equilibrium")
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{
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Su == SuInf;
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}
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else if (SuModel == "transport")
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{
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// Solve for the strained laminar flame speed
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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volScalarField Rc =
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(sigmas*SuInf*(Su0 - SuInf) + sqr(SuMin)*sigmaExt)
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/(sqr(Su0 - SuInf) + sqr(SuMin));
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fvScalarMatrix SuEqn
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(
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fvm::ddt(rho, Su)
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+ fvm::div(phi + phiXi, Su, "div(phiXi,Su)")
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+ fvm::SuSp(-fvc::div(phiXi), Su)
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==
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- fvm::SuSp(-rho*Rc*Su0/Su, Su)
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- fvm::SuSp(rho*(sigmas + Rc), Su)
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);
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SuEqn.relax();
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SuEqn.solve();
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// Limit the maximum Su
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// ~~~~~~~~~~~~~~~~~~~~
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Su.min(SuMax);
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Su.max(SuMin);
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}
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else
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{
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FatalError
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<< args.executable() << " : Unknown Su model " << SuModel
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<< abort(FatalError);
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}
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// Calculate Xi according to the selected flame wrinkling model
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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if (XiModel == "fixed")
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{
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// Do nothing, Xi is fixed!
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}
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else if (XiModel == "algebraic")
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{
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// Simple algebraic model for Xi based on Gulders correlation
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// with a linear correction function to give a plausible profile for Xi
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Xi == scalar(1) +
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(scalar(1) + (2*XiShapeCoef)*(scalar(0.5) - b))
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*XiCoef*sqrt(up/(Su + SuMin))*Reta;
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}
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else if (XiModel == "transport")
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{
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// Calculate Xi transport coefficients based on Gulders correlation
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// and DNS data for the rate of generation
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// with a linear correction function to give a plausible profile for Xi
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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volScalarField XiEqStar =
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scalar(1.001) + XiCoef*sqrt(up/(Su + SuMin))*Reta;
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volScalarField XiEq =
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scalar(1.001)
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+ (scalar(1) + (2*XiShapeCoef)*(scalar(0.5) - b))
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*(XiEqStar - scalar(1.001));
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volScalarField Gstar = 0.28/tauEta;
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volScalarField R = Gstar*XiEqStar/(XiEqStar - scalar(1));
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volScalarField G = R*(XiEq - scalar(1.001))/XiEq;
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//R *= (Gstar + 2*mag(dev(symm(fvc::grad(U)))))/Gstar;
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// Solve for the flame wrinkling
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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fvScalarMatrix XiEqn
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(
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fvm::ddt(rho, Xi)
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+ fvm::div(phi + phiXi, Xi, "div(phiXi,Xi)")
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+ fvm::SuSp(-fvc::div(phiXi), Xi)
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==
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rho*R
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- fvm::Sp(rho*(R - G), Xi)
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- fvm::Sp
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(
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rho*max
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(
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sigmat - sigmas,
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dimensionedScalar("0", sigmat.dimensions(), 0)
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),
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Xi
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)
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);
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XiEqn.relax();
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XiEqn.solve();
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// Correct boundedness of Xi
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// ~~~~~~~~~~~~~~~~~~~~~~~~~
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Xi.max(1.0);
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Info<< "max(Xi) = " << max(Xi).value() << endl;
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Info<< "max(XiEq) = " << max(XiEq).value() << endl;
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}
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else
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{
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FatalError
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<< args.executable() << " : Unknown Xi model " << XiModel
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<< abort(FatalError);
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}
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Info<< "Combustion progress = "
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<< 100*(scalar(1) - b)().weightedAverage(mesh.V()).value() << "%"
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<< endl;
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St = Xi*Su;
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}
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