Adaptive Mesh Refinement With a Moving Mesh using...

Adaptive Mesh Refinement With a Moving Meshusing sprayDyMFoam

Andreas Nygren

Chalmers University of TechnologyDivision of Combustion

8-9th of DecemberOpenFoam Course

Andreas Nygren OpenFoam Course - December 8-9 2015

Introduction

Motivation

• To properly resolve the physics, fine meshes are needed inregions of interest.

• It is computationally expensive to make the whole mesh veryfine.

• For automotive applications moving meshes are used to modelpiston movement.


Introduction

Learning Outcomes

Today you will learn how to:

• How to combine the dynamicRefineFvMesh class withthedynamicMotionSolverFvMesh class

• Modify sprayDyMFoam to calculate and output the gradientof the velocity field to be used as basis for the adaptive meshrefinement.

• How to set-up a case with mesh motion and on-line adaptivemesh refinement.


Introduction

Dynamic Mesh Libraries in OpenFOAM

dynamicFvMesh

• dynamicMotionSolverFvMesh• dynamicRefineFvMesh• solidBodyMotionFvMesh• dynamicInkJetFvMesh

topoChangerFvMesh

• linearValveFvMesh• linearValveLayersFvMesh• mixerFvMesh• movingConeTopoFvMesh• rawTopoChangerFvMesh


Introduction

Dynamic Mesh Libraries in OpenFOAM

dynamicFvMesh

• dynamicMotionSolverFvMesh• dynamicRefineFvMesh• solidBodyMotionFvMesh• dynamicInkJetFvMesh

topoChangerFvMesh

• linearValveFvMesh• linearValveLayersFvMesh• mixerFvMesh• movingConeTopoFvMesh• rawTopoChangerFvMesh

Focus on simple mesh motion with mesh refinement!


Mesh Refinement with Motion

First off!

• Combine dynamicRefineFvMesh anddynamicMotionSolverFvMesh

• Create a library for both mesh motion and refinement



Copy and rename

Start by copying dynamicRefineFvMesh to your own folder

OF30x

mkdir -p $FOAM_RUN/../src/motionRefinementFvMesh/

cd $FOAM_RUN/../src/motionRefinementFvMesh/

cp -r $FOAM_SRC/dynamicFvMesh/dynamicRefineFvMesh .

mv dynamicRefineFvMesh dynamicMotionSolverRefineFvMesh

cd dynamicMotionSolverRefineFvMesh

mv dynamicRefineFvMesh.C dynamicMotionSolverRefineFvMesh.C

mv dynamicRefineFvMesh.H dynamicMotionSolverRefineFvMesh.H



Renaming Inside Files

• Function calls and includes etc need to be renamed to thenew class name

• Use the sed command!

sed commandsed -i s/dynamicRefineFvMesh/dynamicMotionSolverRefineFvMesh/g dynamicMotionSolverRefineFvMesh.C

sed -i s/dynamicRefineFvMesh/dynamicMotionSolverRefineFvMesh/g dynamicMotionSolverRefineFvMesh.H

• A Convenient and safe way to change the name



Edit dynamicMotionSolverRefineFvMesh.H

Class Declaration for motionSolvernamespace Foam

{

// Add Class Declaration for the Motion Solver Class

class motionSolver;

Declare a pointer to the motionSolver

class dynamicMotionSolverRefineFvMesh

:

public dynamicFvMesh

{

//Add declaration for pointer to Motion Solver

autoPtr motionPtr_;

protected:



Edit dynamicMotionSolverRefineFvMesh.C

Includes for the Motion Solver#include "dynamicMotionSolverRefineFvMesh.H"

#include "addToRunTimeSelectionTable.H"

#include "surfaceInterpolate.H"

#include "volFields.H"

#include "polyTopoChange.H"

#include "surfaceFields.H"

#include "syncTools.H"

#include "pointFields.H"

#include "sigFpe.H"

#include "cellSet.H"

// Add the Following Includes to the Header:

#include "motionSolver.H"

#include "mapPolyMesh.H"

#include "pointField.H"



Edit dynamicMotionSolverRefineFvMesh.C

Pointer to the motionSolver object in the ConstructordynamicFvMesh(io),

//define a pointer to the motionSolver Object in the Constructor:

motionPtr_(motionSolver::New(*this)),

meshCutter_(*this),

dumpLevel_(false),

nRefinementIterations_(0),

protectedCell_(nCells(), 0)

function call to move pointsbool Foam::dynamicMotionSolverRefineFvMesh::update()

{

// Add a function call to the motionSolver

// to move points before refinement.

dynamicFvMesh::movePoints(motionPtr_->newPoints());



Create a Make folder

Copy the Make folder from dynamicFvMesh

cd ..

cp -r $FOAM_SRC/dynamicFvMesh/Make .

Edit Make/files

dynamicMotionSolverRefineFvMesh/dynamicMotionSolverRefineFvMesh.C

LIB = $(FOAM_USER_LIBBIN)/libmotionRefinementFvMesh



Make/options link with dynamicFvMesh

EXE_INC = \

-I$(LIB_SRC)/triSurface/lnInclude \

-I$(LIB_SRC)/meshTools/lnInclude \

-I$(LIB_SRC)/dynamicMesh/lnInclude \

-I$(LIB_SRC)/dynamicFvMesh/lnInclude \

-I$(LIB_SRC)/finiteVolume/lnInclude

LIB_LIBS = \

-ltriSurface \

-lmeshTools \

-ldynamicMesh \

-ldynamicFvMesh \

-lfiniteVolume



Clean and Compile!

Makewclean

wmake


Mesh Refinement Based on a Gradient

• It is known that the mesh should be refined where thegradient of a field is high.

• We can base our mesh refinement on the gradient of a fieldrather than the field itself.

• We just need to calculate the gradient of the field every timestep

• An easy way of doing this is to just modify the solver



Copying The Files

Copy and rename sprayDyMFoammkdir -p $FOAM_RUN/../applications/solvers/mySprayDyMFoam

cd $FOAM_RUN/../applications/solvers/mySprayDyMFoam

cp $FOAM_SOLVERS/lagrangian/sprayFoam/createClouds.H .

cp $FOAM_SOLVERS/lagrangian/sprayFoam/createFields.H .

cp $FOAM_SOLVERS/lagrangian/sprayFoam/rhoEqn.H .

cp $FOAM_SOLVERS/lagrangian/sprayFoam/UEqn.H .

cp $FOAM_SOLVERS/lagrangian/sprayFoam/sprayDyMFoam/pEqn.H .

cp $FOAM_SOLVERS/lagrangian/sprayFoam/sprayDyMFoam/sprayDyMFoam.C .

cp -r $FOAM_SOLVERS/lagrangian/sprayFoam/sprayDyMFoam/Make .

mv sprayDyMFoam.C mySprayDyMFoam.C



Initialize The Gradient Field

Add to createFields.H

// Initialize After U!

volScalarField UGrad

(

IOobject

(

"UGrad",

runTime.timeName(),

mesh,

IOobject::READ_IF_PRESENT,

IOobject::AUTO_WRITE

),

mag(fvc::grad(U))

);



Modify the Solver

Add gradient calculation

// Store momentum to set rhoUf for introduced faces.

volVectorField rhoU("rhoU", rho*U);

// Add the calculation of the velocity

// gradient before the mesh changes

UGrad = mag(fvc::grad(U));

// Do any mesh changes

mesh.update();



Create Make/files, Make/options and compile

Make/files - Change Name

mySprayDyMFoam.C

EXE = $(FOAM_USER_APPBIN)/mySprayDyMFoam

Make/options - Change the Path to Two Folders

-I$(FOAM_SOLVERS)/lagrangian/reactingParcelFoam \

-I$(FOAM_SOLVERS)/compressible/rhoPimpleFoam/rhoPimpleDyMFoam \

Clean and Compile!

wclean

wmake


Case Set-Up

Aachen-Bomb case

• Static Spray combustionchamber

• sprayFoam tutorial case• We can modify it to run

with dynamicMotionSolver-RefineFvMesh


Case Set-Up

• Download the aachenBombMotionRefine case.• It has been modified so that the spray chamber will shrink

during run-time.

• It serve to illustrate the simultaneous mesh motion andrefinement.

• This is not a ”real spray simulation”. The mesh is to coarse.• We will now go through the modifications and then run the

case.


Case Set-Up

Add patches for movingWall

patches

(

wall walls

(

(2 6 5 1)

(0 4 7 3)

(0 1 5 4)

(7 6 2 3)

)

wall fixedWall

(

(4 5 6 7)

)

wall movingWall

(

(0 1 2 3)

)

);


Case Set-Up

Modify inital files to correspond to new patches

boundaryField

{

walls

{

type zeroGradient;

}

fixedWall

{

type zeroGradient;

}

movingWall

{

type zeroGradient;

}

}


Case Set-Up

Moving Wall velocity for U

movingWall

{

type movingWallVelocity;

value uniform (0 0 0);

}


Case Set-Up

pointMotion

dimensions [ 0 1 -1 0 0 0 0 ];

internalField uniform 0;

boundaryField

{

movingWall

{

type uniformFixedValue;

uniformValue 1;

value uniform 1;

}

walls

{

type slip;

}

fixedWall

{

type uniformFixedValue;

uniformValue 0;

value uniform 0;

}

}

• Special Inital File• Prescribe velocity for mesh

points at movingWall


Case Set-Up

dynamicMeshDict - Motion Coeffs

dynamicFvMesh dynamicMotionSolverRefineFvMesh;

motionSolverLibs ( "libfvMotionSolvers.so" );

solver

velocityComponentLaplacian;

velocityComponentLaplacianCoeffs

{

component

y;

diffusivity

inverseDistance (movingWall);

}


Case Set-Up

dynamicMeshDict - Refinement CoeffsdynamicMotionSolverRefineFvMeshCoeffs

//dynamicRefineFvMeshCoeffs

{

// How often to refine

refineInterval 1;

// Field to be refinement on

field

UGrad;

// Refine field inbetween lower..upper

lowerRefineLevel 10000;

upperRefineLevel 70000;

// If value < unrefineLevel unrefine

unrefineLevel

1;

// Have slower than 2:1 refinement

nBufferLayers

1;

// Refine cells only up to maxRefinement levels

maxRefinement

2;

// Stop refinement if maxCells reached

maxCells

160000;

// Flux field and corresponding velocity field. Fluxes on changed

// faces get recalculated by interpolating the velocity. Use none

// on surfaceScalarFields that do not need to be reinterpolated.

correctFluxes

(

(phi_0 U_0)

(phi U)


Results

Figure: Inital Temperature Field andMesh

Figure: Temperature Field and Meshafter 0.006 seconds


IntroductionMesh Refinement with MotionMesh Refinement Based on a GradientCase Set-UpResults

Adaptive Mesh Refinement With a Moving Mesh using...

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