Foam::scalar Foam::VariableHardSphere<CloudType>::sigmaTcR
(
const typename CloudType::parcelType& pP,
const typename CloudType::parcelType& pQ
) const
{
const CloudType& cloud(this->owner());
label typeIdP = pP.typeId();
label typeIdQ = pQ.typeId();
scalar dPQ =
0.5
*(
cloud.constProps(typeIdP).d()
+ cloud.constProps(typeIdQ).d()
);
scalar omegaPQ =
0.5
*(
cloud.constProps(typeIdP).omega()
+ cloud.constProps(typeIdQ).omega()
);
scalar cR = mag(pP.U() - pQ.U());
if (cR < VSMALL)
{
return 0;
}
scalar mP = cloud.constProps(typeIdP).mass();
scalar mQ = cloud.constProps(typeIdQ).mass();
scalar mR = mP*mQ/(mP + mQ);
// calculating cross section = pi*dPQ^2, where dPQ is from Bird, eq. 4.79
scalar sigmaTPQ =
pi*dPQ*dPQ
*pow(2.0*physicoChemical::k.value()*Tref_/(mR*cR*cR), omegaPQ - 0.5)
/exp(Foam::lgamma(2.5 - omegaPQ));
return sigmaTPQ*cR;
}
void Foam::VariableHardSphere<CloudType>::collide
(
typename CloudType::parcelType& pP,
typename CloudType::parcelType& pQ
)
{
CloudType& cloud(this->owner());
label typeIdP = pP.typeId();
label typeIdQ = pQ.typeId();
vector& UP = pP.U();
vector& UQ = pQ.U();
Random& rndGen(cloud.rndGen());
scalar mP = cloud.constProps(typeIdP).mass();
scalar mQ = cloud.constProps(typeIdQ).mass();
vector Ucm = (mP*UP + mQ*UQ)/(mP + mQ);
scalar cR = mag(UP - UQ);
scalar cosTheta = 2.0*rndGen.scalar01() - 1.0;
scalar sinTheta = sqrt(1.0 - cosTheta*cosTheta);
scalar phi = twoPi*rndGen.scalar01();
vector postCollisionRelU =
cR
*vector
(
cosTheta,
sinTheta*cos(phi),
sinTheta*sin(phi)
);
UP = Ucm + postCollisionRelU*mQ/(mP + mQ);
UQ = Ucm - postCollisionRelU*mP/(mP + mQ);
}
void Foam::MaxwellianThermal<CloudType>::correct
(
typename CloudType::parcelType& p,
const wallPolyPatch& wpp
)
{
vector& U = p.U();
scalar& Ei = p.Ei();
label typeId = p.typeId();
label wppIndex = wpp.index();
label wppLocalFace = wpp.whichFace(p.face());
vector nw = p.normal();
nw /= mag(nw);
// Normal velocity magnitude
scalar U_dot_nw = U & nw;
// Wall tangential velocity (flow direction)
vector Ut = U - U_dot_nw*nw;
CloudType& cloud(this->owner());
Random& rndGen(cloud.rndGen());
while (mag(Ut) < SMALL)
{
// If the incident velocity is parallel to the face normal, no
// tangential direction can be chosen. Add a perturbation to the
// incoming velocity and recalculate.
U = vector
(
U.x()*(0.8 + 0.2*rndGen.scalar01()),
U.y()*(0.8 + 0.2*rndGen.scalar01()),
U.z()*(0.8 + 0.2*rndGen.scalar01())
);
U_dot_nw = U & nw;
Ut = U - U_dot_nw*nw;
}
// Wall tangential unit vector
vector tw1 = Ut/mag(Ut);
// Other tangential unit vector
vector tw2 = nw^tw1;
scalar T = cloud.boundaryT().boundaryField()[wppIndex][wppLocalFace];
scalar mass = cloud.constProps(typeId).mass();
scalar iDof = cloud.constProps(typeId).internalDegreesOfFreedom();
U =
sqrt(physicoChemical::k.value()*T/mass)
*(
rndGen.GaussNormal()*tw1
+ rndGen.GaussNormal()*tw2
- sqrt(-2.0*log(max(1 - rndGen.scalar01(), VSMALL)))*nw
);
U += cloud.boundaryU().boundaryField()[wppIndex][wppLocalFace];
Ei = cloud.equipartitionInternalEnergy(T, iDof);
}
void Foam::MixedDiffuseSpecular<CloudType>::correct
(
typename CloudType::parcelType& p
)
{
vector& U = p.U();
scalar& Ei = p.Ei();
label typeId = p.typeId();
const label wppIndex = p.patch();
const polyPatch& wpp = p.mesh().boundaryMesh()[wppIndex];
label wppLocalFace = wpp.whichFace(p.face());
const vector nw = p.normal();
// Normal velocity magnitude
scalar U_dot_nw = U & nw;
CloudType& cloud(this->owner());
Random& rndGen(cloud.rndGen());
if (diffuseFraction_ > rndGen.scalar01())
{
// Diffuse reflection
// Wall tangential velocity (flow direction)
vector Ut = U - U_dot_nw*nw;
while (mag(Ut) < small)
{
// If the incident velocity is parallel to the face normal, no
// tangential direction can be chosen. Add a perturbation to the
// incoming velocity and recalculate.
U = vector
(
U.x()*(0.8 + 0.2*rndGen.scalar01()),
U.y()*(0.8 + 0.2*rndGen.scalar01()),
U.z()*(0.8 + 0.2*rndGen.scalar01())
);
U_dot_nw = U & nw;
Ut = U - U_dot_nw*nw;
}
// Wall tangential unit vector
vector tw1 = Ut/mag(Ut);
// Other tangential unit vector
vector tw2 = nw^tw1;
scalar T = cloud.boundaryT().boundaryField()[wppIndex][wppLocalFace];
scalar mass = cloud.constProps(typeId).mass();
direction iDof = cloud.constProps(typeId).internalDegreesOfFreedom();
U =
sqrt(physicoChemical::k.value()*T/mass)
*(
rndGen.scalarNormal()*tw1
+ rndGen.scalarNormal()*tw2
- sqrt(-2.0*log(max(1 - rndGen.scalar01(), vSmall)))*nw
);
U += cloud.boundaryU().boundaryField()[wppIndex][wppLocalFace];
Ei = cloud.equipartitionInternalEnergy(T, iDof);
}
else
{
// Specular reflection
if (U_dot_nw > 0.0)
{
U -= 2.0*U_dot_nw*nw;
}
}
}
void Foam::LarsenBorgnakkeVariableHardSphere<CloudType>::collide
(
typename CloudType::parcelType& pP,
typename CloudType::parcelType& pQ
)
{
CloudType& cloud(this->owner());
label typeIdP = pP.typeId();
label typeIdQ = pQ.typeId();
vector& UP = pP.U();
vector& UQ = pQ.U();
scalar& EiP = pP.Ei();
scalar& EiQ = pQ.Ei();
Random& rndGen(cloud.rndGen());
scalar inverseCollisionNumber = 1/relaxationCollisionNumber_;
// Larsen Borgnakke internal energy redistribution part. Using the serial
// application of the LB method, as per the INELRS subroutine in Bird's
// DSMC0R.FOR
scalar preCollisionEiP = EiP;
scalar preCollisionEiQ = EiQ;
direction iDofP = cloud.constProps(typeIdP).internalDegreesOfFreedom();
direction iDofQ = cloud.constProps(typeIdQ).internalDegreesOfFreedom();
scalar omegaPQ =
0.5
*(
cloud.constProps(typeIdP).omega()
+ cloud.constProps(typeIdQ).omega()
);
scalar mP = cloud.constProps(typeIdP).mass();
scalar mQ = cloud.constProps(typeIdQ).mass();
scalar mR = mP*mQ/(mP + mQ);
vector Ucm = (mP*UP + mQ*UQ)/(mP + mQ);
scalar cRsqr = magSqr(UP - UQ);
scalar availableEnergy = 0.5*mR*cRsqr;
scalar ChiB = 2.5 - omegaPQ;
if (iDofP > 0)
{
if (inverseCollisionNumber > rndGen.scalar01())
{
availableEnergy += preCollisionEiP;
if (iDofP == 2)
{
scalar energyRatio = 1.0 - pow(rndGen.scalar01(), (1.0/ChiB));
EiP = energyRatio*availableEnergy;
}
else
{
scalar ChiA = 0.5*iDofP;
EiP = energyRatio(ChiA, ChiB)*availableEnergy;
}
availableEnergy -= EiP;
}
}
if (iDofQ > 0)
{
if (inverseCollisionNumber > rndGen.scalar01())
{
availableEnergy += preCollisionEiQ;
if (iDofQ == 2)
{
scalar energyRatio = 1.0 - pow(rndGen.scalar01(), (1.0/ChiB));
EiQ = energyRatio*availableEnergy;
}
else
{
scalar ChiA = 0.5*iDofQ;
EiQ = energyRatio(ChiA, ChiB)*availableEnergy;
}
availableEnergy -= EiQ;
}
}
// Rescale the translational energy
scalar cR = sqrt(2.0*availableEnergy/mR);
// Variable Hard Sphere collision part
scalar cosTheta = 2.0*rndGen.scalar01() - 1.0;
scalar sinTheta = sqrt(1.0 - cosTheta*cosTheta);
scalar phi = twoPi*rndGen.scalar01();
vector postCollisionRelU =
cR
*vector
(
cosTheta,
sinTheta*cos(phi),
sinTheta*sin(phi)
);
UP = Ucm + postCollisionRelU*mQ/(mP + mQ);
UQ = Ucm - postCollisionRelU*mP/(mP + mQ);
}