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Lagrangian: Rewrite of the particle tracking algorithm to function in

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terms of the local barycentric coordinates of the current tetrahedron,
rather than the global coordinate system.

Barycentric tracking works on any mesh, irrespective of mesh quality.
Particles do not get "lost", and tracking does not require ad-hoc
"corrections" or "rescues" to function robustly, because the calculation
of particle-face intersections is unambiguous and reproducible, even at
small angles of incidence.

Each particle position is defined by topology (i.e. the decomposed tet
cell it is in) and geometry (i.e. where it is in the cell). No search
operations are needed on restart or reconstruct, unlike when particle
positions are stored in the global coordinate system.

The particle positions file now contains particles' local coordinates
and topology, rather than the global coordinates and cell. This change
to the output format is not backwards compatible. Existing cases with
Lagrangian data will not restart, but they will still run from time
zero without any modification. This change was necessary in order to
guarantee that the loaded particle is valid, and therefore
fundamentally prevent "loss" and "search-failure" type bugs (e.g.,
2517, 2442, 2286, 1836, 1461, 1341, 1097).

The tracking functions have also been converted to function in terms
of displacement, rather than end position. This helps remove floating
point error issues, particularly towards the end of a tracking step.

Wall bounded streamlines have been removed. The implementation proved
incompatible with the new tracking algorithm. ParaView has a surface
LIC plugin which provides equivalent, or better, functionality.

Additionally, bug report <https://bugs.openfoam.org/view.php?id=2517>
is resolved by this change.
This commit is contained in:
Will Bainbridge
2017-04-28 08:03:44 +01:00
committed by Andrew Heather
parent dd3be135de
commit 743dea87d2
91 changed files with 3209 additions and 2443 deletions
Download Patch File Download Diff File Expand all files Collapse all files

104
src/functionObjects/field/streamLine/streamLineParticle.C
View File

@ -2,7 +2,7 @@
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration |
\\ / A nd | Copyright (C) 2011-2016 OpenFOAM Foundation
\\ / A nd | Copyright (C) 2011-2017 OpenFOAM Foundation
\\/ M anipulation |
-------------------------------------------------------------------------------
License
@ -26,35 +26,8 @@ License
#include "streamLineParticle.H"
#include "vectorFieldIOField.H"
// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
namespace Foam
{
// defineParticleTypeNameAndDebug(streamLineParticle, 0);
}
// * * * * * * * * * * * * * Private Member Functions * * * * * * * * * * * //
Foam::scalar Foam::streamLineParticle::calcSubCycleDeltaT
(
trackingData& td,
const scalar dt,
const vector& U
) const
{
particle testParticle(*this);
bool oldKeepParticle = td.keepParticle;
bool oldSwitchProcessor = td.switchProcessor;
scalar fraction = testParticle.trackToFace(position()+dt*U, td);
td.keepParticle = oldKeepParticle;
td.switchProcessor = oldSwitchProcessor;
// Adapt the dt to subdivide the trajectory into substeps.
return dt*fraction/td.nSubCycle_;
}
Foam::vector Foam::streamLineParticle::interpolateFields
(
const trackingData& td,
@ -129,7 +102,6 @@ Foam::streamLineParticle::streamLineParticle
{
if (readFields)
{
//if (is.format() == IOstream::ASCII)
List<scalarList> sampledScalars;
List<vectorList> sampledVectors;
@ -169,31 +141,22 @@ Foam::streamLineParticle::streamLineParticle
bool Foam::streamLineParticle::move
(
trackingData& td,
const scalar trackTime
const scalar
)
{
streamLineParticle& p = static_cast<streamLineParticle&>(*this);
td.switchProcessor = false;
td.keepParticle = true;
scalar tEnd = (1.0 - stepFraction())*trackTime;
scalar maxDt = mesh_.bounds().mag();
const scalar maxDt = mesh().bounds().mag();
while
(
td.keepParticle
&& !td.switchProcessor
&& lifeTime_ > 0
)
while (td.keepParticle && !td.switchProcessor && lifeTime_ > 0)
{
// set the lagrangian time-step
scalar dt = maxDt;
// Cross cell in steps:
// - at subiter 0 calculate dt to cross cell in nSubCycle steps
// - at the last subiter do all of the remaining track
for (label subIter = 0; subIter < td.nSubCycle_; subIter++)
for (label subIter = 0; subIter < max(1, td.nSubCycle_); subIter++)
{
--lifeTime_;
@ -219,37 +182,27 @@ bool Foam::streamLineParticle::move
if (td.trackLength_ < GREAT)
{
// No sub-cycling. Track a set length on each step.
dt = td.trackLength_;
//Pout<< " subiteration " << subIter
// << " : fixed length: updated dt:" << dt << endl;
}
else if (subIter == 0 && td.nSubCycle_ > 1)
else if (subIter == 0)
{
// Adapt dt to cross cell in a few steps
dt = calcSubCycleDeltaT(td, dt, U);
// Sub-cycling. Cross the cell in nSubCycle steps.
particle copy(*this);
copy.trackToFace(maxDt*U, 1);
dt *= (copy.stepFraction() - stepFraction())/td.nSubCycle_;
}
else if (subIter == td.nSubCycle_ - 1)
{
// Do full step on last subcycle
// Sub-cycling. Track the whole cell on the last step.
dt = maxDt;
}
scalar fraction = trackToFace(position() + dt*U, td);
dt *= fraction;
tEnd -= dt;
stepFraction() = 1.0 - tEnd/trackTime;
if (tEnd <= ROOTVSMALL)
{
// Force removal
lifeTime_ = 0;
}
trackToFace(dt*U, 0, td);
if
(
face() != -1
onFace()
|| !td.keepParticle
|| td.switchProcessor
|| lifeTime_ == 0
@ -260,17 +213,16 @@ bool Foam::streamLineParticle::move
}
}
if (!td.keepParticle || lifeTime_ == 0)
{
if (lifeTime_ == 0)
{
// Failure exit. Particle stagnated or it's life ran out.
if (debug)
{
Pout<< "streamLineParticle : Removing stagnant particle:"
<< p.position()
<< " sampled positions:" << sampledPositions_.size()
<< endl;
Pout<< "streamLineParticle: Removing stagnant particle:"
<< position() << " sampled positions:"
<< sampledPositions_.size() << endl;
}
td.keepParticle = false;
}
@ -282,29 +234,25 @@ bool Foam::streamLineParticle::move
if (debug)
{
Pout<< "streamLineParticle : Removing particle:"
<< p.position()
Pout<< "streamLineParticle: Removing particle:" << position()
<< " sampled positions:" << sampledPositions_.size()
<< endl;
}
}
// Transfer particle data into trackingData.
//td.allPositions_.append(sampledPositions_);
td.allPositions_.append(vectorList());
vectorList& top = td.allPositions_.last();
top.transfer(sampledPositions_);
forAll(sampledScalars_, i)
{
//td.allScalars_[i].append(sampledScalars_[i]);
td.allScalars_[i].append(scalarList());
scalarList& top = td.allScalars_[i].last();
top.transfer(sampledScalars_[i]);
}
forAll(sampledVectors_, i)
{
//td.allVectors_[i].append(sampledVectors_[i]);
td.allVectors_[i].append(vectorList());
vectorList& top = td.allVectors_[i].last();
top.transfer(sampledVectors_[i]);
@ -428,18 +376,11 @@ void Foam::streamLineParticle::readFields(Cloud<streamLineParticle>& c)
);
c.checkFieldIOobject(c, sampledPositions);
// vectorFieldIOField sampleVelocity
// (
// c.fieldIOobject("sampleVelocity", IOobject::MUST_READ)
// );
// c.checkFieldIOobject(c, sampleVelocity);
label i = 0;
forAllIter(Cloud<streamLineParticle>, c, iter)
{
iter().lifeTime_ = lifeTime[i];
iter().sampledPositions_.transfer(sampledPositions[i]);
// iter().sampleVelocity_.transfer(sampleVelocity[i]);
i++;
}
}
@ -461,24 +402,17 @@ void Foam::streamLineParticle::writeFields(const Cloud<streamLineParticle>& c)
c.fieldIOobject("sampledPositions", IOobject::NO_READ),
np
);
// vectorFieldIOField sampleVelocity
// (
// c.fieldIOobject("sampleVelocity", IOobject::NO_READ),
// np
// );
label i = 0;
forAllConstIter(Cloud<streamLineParticle>, c, iter)
{
lifeTime[i] = iter().lifeTime_;
sampledPositions[i] = iter().sampledPositions_;
// sampleVelocity[i] = iter().sampleVelocity_;
i++;
}
lifeTime.write();
sampledPositions.write();
// sampleVelocity.write();
}