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========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Copyright (C) 2015-2026 OpenFOAM Foundation
\\/ M anipulation |
-------------------------------------------------------------------------------
License
This file is part of OpenFOAM.
OpenFOAM is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
Class
Foam::patchDistMethods::advectionDiffusion
Description
Calculation of approximate distance to nearest patch for all cells and
boundary by solving the Eikonal equation in advection form with diffusion
smoothing.
If the diffusion coefficient is set to 0 this method is exact in principle
but the numerical schemes used are not rendering the scheme approximate, but
more accurate than the Poisson method. Also many models relying on the
distance to the wall benefit from this field being smooth and monotonic so
the addition of diffusion smoothing improves both the convergence and
stability of the solution of the Eikonal equation and the behavior of the
models using the distance field generated. However, it is not clear what
the optimum value for the diffusion coefficient epsilon should be; a
default value of 0.1 is provided but higher values may be preferable under
some circumstances.
Convergence is accelerated by first generating an approximate solution
using one of the simpler methods, e.g. Poisson. The method used for
this prediction step is specified in the 'advectionDiffusionCoeffs'
sub-dictionary, see below.
References:
\verbatim
P.G. Tucker, C.L. Rumsey, R.E. Bartels, R.T. Biedron,
"Transport equation based wall distance computations aimed at flows
with time-dependent geometry",
NASA/TM-2003-212680, December 2003.
\endverbatim
Example of the wallDist specification in fvSchemes:
\verbatim
laplacianSchemes
{
.
.
laplacian(yPsi) Gauss linear corrected;
laplacian(yWall) Gauss linear corrected;
.
.
}
wallDist
{
method advectionDiffusion;
// Optional entry enabling the calculation
// of the normal-to-wall field
nRequired false;
advectionDiffusion
{
method Poisson;
epsilon 0.1;
tolerance 1e-3;
maxIter 10;
}
}
\endverbatim
Also the solver specification for yWall is required in fvSolution, e.g.
for simple cases:
\verbatim
yPsi
{
solver PCG;
preconditioner DIC;
tolerance 1e-4;
relTol 0;
}
yWall
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-4;
relTol 0;
}
relaxationFactors
{
equations
{
.
.
yWall 1;
.
.
}
}
or for more complex cases:
yPsi
{
solver GAMG;
smoother GaussSeidel;
tolerance 1e-4;
relTol 0;
}
yWall
{
solver GAMG;
smoother symGaussSeidel;
tolerance 1e-4;
relTol 0;
}
relaxationFactors
{
equations
{
.
.
yWall 0.7;
.
.
}
}
\endverbatim
See also
Foam::patchDistMethod::Poisson
Foam::patchDistMethod::meshWave
Foam::wallDist
SourceFiles
advectionDiffusionPatchDistMethod.C
\*---------------------------------------------------------------------------*/
#ifndef advectionDiffusionPatchDistMethod_H
#define advectionDiffusionPatchDistMethod_H
#include "patchDistMethod.H"
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
namespace Foam
{
namespace patchDistMethods
{
/*---------------------------------------------------------------------------*\
Class advectionDiffusion Declaration
\*---------------------------------------------------------------------------*/
class advectionDiffusion
:
public patchDistMethod
{
// Private Data
//- Sub-dictionary of coefficients
dictionary coeffs_;
//- Run-time selected method to predict the distance-to-wall field
autoPtr<patchDistMethod> pdmPredictor_;
//- Diffusion coefficient multiplying y*laplacian(y)
scalar epsilon_;
//- Convergence tolerance for the iterations of the advection-diffusion
// equation to correct the distance-to-patch and normal-to-patch fields
scalar tolerance_;
//- Maximum number of iterations of the advection-diffusion equation
// to correct the distance-to-patch and normal-to-patch fields
int maxIter_;
//- Flag to indicate the predictor step has been executed
bool predicted_;
public:
//- Runtime type information
TypeName("advectionDiffusion");
// Constructors
//- Construct from coefficients dictionary, mesh
// and fixed-value patch set
advectionDiffusion
(
const dictionary& dict,
const fvMesh& mesh,
const labelHashSet& patchIDs
);
//- Disallow default bitwise copy construction
advectionDiffusion(const advectionDiffusion&) = delete;
// Member Functions
//- Correct the given distance-to-patch field
virtual bool correct(volScalarField& y);
//- Correct the given distance-to-patch and normal-to-patch fields
virtual bool correct(volScalarField& y, volVectorField& n);
// Member Operators
//- Disallow default bitwise assignment
void operator=(const advectionDiffusion&) = delete;
};
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
} // End namespace patchDistMethods
} // End namespace Foam
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
#endif
// ************************************************************************* //
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