Implementation of multiple deltaTs for the multi-region solver based - - PowerPoint PPT Presentation

Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Implementation of multiple deltaTs for the multi-region solver based on chtMultiRegionFoam

Yuzhu Pearl Li

Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, Stavanger, Norway

2016-12-5

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Outline

Outline

This work is to demonstrate the structure of chtMultiRegionFoam solver in FOAM-extend-4.0 and to implement modifications upon it. Introduction A walk through the solvers Multi-region loop modifications Verification: Try with the new solver Pressure coupled boundary condition Summary and future work

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Introduction

Introduction

Multi-physics(multi-region) problems chtMultiRegionFoam Solver modifications

*Note that the chtMultiRegionFoam in Foam-extend-4.0 has differences from the version in OpenFOAM-4.0. This work may not be able to directly applied to

• ther OpenFOAM versions.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Multi-physics(multi-region) problems

Multi-physics(multi-region) problems

Conjugate Heat Transfer Wave-Structure-Soil Interaction A multi-physics problem has multiple physical domains; the interaction between the domains are achieved by boundary condition update. For some multi-physics problems, it is not efficient to calculate the multiple regions with the same mesh size and time step.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Multi-physics(multi-region) problems

Conjugate heat transfer and wave-structure-soil interaction

The modification of the chtMultiRegionFoam is regarded as an initial step to develop a wave-structure-soil (WSS) interaction solver. chtMultiRegionFoam: heat transfer (Kappa, T) between fluid and solid regions. Wave-structure-soil Interaction: pressure transfer (p) from fluid to solid regions.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and chtMultiRegionFoam

chtMultiRegionFoam

What and why? The chtMultiRegionFoam is a multi-regional(multi-physics) solver working on fluid and solid regions. The chtMultiRegionFoam contains solvers for each domain and they are coupled by boundary condition update. The physical feature of the conjugate heat transfer is one-way coupling, from the high temperature regions to the low temperature regions. The chtMultiRegionFoam is a transient solver (while chtMultiRegionSimpleFoam is a steady-state solver).

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Solver modifications

Solver modifications

Based on chtMultiRegionFoam, Loop modification with multiple deltaTs (two approaches) Solver verifications by case study Pressure coupled boundary condition

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

A walk through the chtMultiRegionFoam solver

|----- chtMultiRegionFoam.C |----- fluid | |----- ... | |----- solveFluid.H |----- solid |----- ... |----- solveSolid.H |----- derivedFvPatchFields | |----- solidWallHeatFluxTemperature | |----- solidWallMixedTemperatureCoupled |----- regionProperties |----- include |----- readPIMPLEControls.H |----- Make

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

A walk through the chtMultiRegionFoam solver

chtMultiRegionFoam.C, the main source file, calls the needed files and solvers. regionProperties/ reads fluid and solid region names setted in the constant/regionProperties of the case files. fluid/ contains source files that solve equations forcontinuity momentum, enthalpy, pressure for the fluid regions. solid/ contains source files for solving heat conduction equation in solid regions. derivedFvPatchFields/ contains files that set new boundary conditions for the coupling between solid and fluid domains. include/ contains files to set/reset the multi-region time step. Make/ contains files for compilation purpose.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and chtMultiRegionFoam.C

chtMultiRegionFoam.C

The source file of chtMultiRegionFoam.C provides a main clue of how is the solver constructed. It can be viewed by f40NR cd $FOAM_SOLVERS/heatTransfer/chtMultiRegionFoam vi chtMultiRegionFoam.C

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and PIMPLE loop

The PIMPLE loop in chtMultiRegionFoam.C

for (int oCorr=0; oCorr<nOuterCorr; oCorr++) { forAll(fluidRegions, i) { Info<< "\nSolving for fluid region " << fluidRegions[i].name() << endl; #include "setRegionFluidFields.H" #include "readFluidMultiRegionPIMPLEControls.H" #include "solveFluid.H" } forAll(solidRegions, i) { Info<< "\nSolving for solid region " << solidRegions[i].name() << endl; #include "setRegionSolidFields.H" #include "readSolidMultiRegionPIMPLEControls.H" #include "solveSolid.H" } }

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and PIMPLE loop

PIMPLE loop

The chtMultiRegionFoam solver uses PIMPLE loop algorithm. PIMPLE algorithm is a combination of the pressure-implicit split-operator (PISO) and the semi-implicit method for pressure-linked equations (SIMPLE) algorithms. The PIMPLE parameters are set in the fvSolution in a case. For example,

PIMPLE { momentumPredictor

• ff;

nOuterCorrectors 1; nCorrectors 2; nNonOrthogonalCorrectors 1; pRefCell 0; pRefValue 0; }

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Fluid solver and solid solver

Fluid solver

The fluid solver solves: density rho pressure p, the derivative of pressure DpDt velocity U thermal energy h h = cp · dT (1) where cp is the specific heat capacity at a constant pressure.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Fluid solver and solid solver

Fluid solver includes four equations:

solveFluid.H

if (oCorr == 0) { #include "rhoEqn.H" //Solve the continuity for density. } #include "UEqn.H" //Solve the momentum equation #include "hEqn.H" //Solve the thermal energy // --- PISO loop for (int corr = 0; corr < nCorr; corr++) { #include "pEqn.H" //solve pressure } turb.correct(); rho = thermo.rho();

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Fluid solver and solid solver

Solid solver

The solid solver solvers temperature T. Variables that are needed for solving the temperature equation are: thermal conductivity (Kappa) specific heat capacity (cp) solid density (rho)

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Fluid solver and solid solver

Solid solver

The solid solver solves the TEqn for solid regions.

tmp<fvScalarMatrix> TEqn ( fvm::ddt(rho*cp, T)

• fvm::laplacian(Kappa, T)

); TEqn().relax(); TEqn().solve(); }

The corresponding mathematical formula for the TEqn is: ρ · cp ∂T ∂t − ∇(KT) = 0 (2) where K denotes Kappa.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Interface boundary coupling

Interface boundary coupling

The solidWallMixedTemperatureCoupled directory defines the mixed coupling boundary condition that the multi-regions are coupled via Dirichlet-Neumann partitioning strategy at the coupled interface: Dirichlet boundary condition: Γ1 = Γ2 (3) where the neighbour patches have the same field value. Neumann boundary condition: ∂Γ1 ∂n1 = ∂Γ2 ∂n2 (4) where the neighbour patches agree on the gradient of the field value.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Interface boundary coupling

Temperature coupled boundary condition

The temperature coupled boundary condition is declared and defined in the directory of derivedFvPatchFields/ solidWallMixedTemperatureCoupled/ : solidWallMixedTemperatureCoupledFvPatchScalarField.H solidWallMixedTemperatureCoupledFvPatchScalarField.C The source file of the boundary condition can be viewed by cd derivedFvPatchFields/solidWallMixedTemperatureCoupled/ vi solidWallMixedTemperatureCoupledFvPatchScalarField.C

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Loop modification: Implementation of multiple deltaTs to the PIMPLE loop

Goal: The goal of the multi-region loop modification is to introduce an extra time step for the solid regions, in addition to the original time step for the fluid regions. Reason: To improve the efficiency of the whole system when the time step requirements varies between different physical regions.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Two approaches

Two approaches of implementation

The first approach. Introduce a time step for the solid regions (solidRegionDeltaT) which is an integral multiple of the fluid region time step (deltaT), i.e. solidRegionDeltaT = n · deltaT (5) where n is an integer. The ’adjustTimeStep’ switch should be turned off.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The first approach

First approach: implementation overview

1 Rename the solver as chtMultiRegionMultiDeltaTFoam. 2 Create a new variable to control the solid region delta T called

• solidRegionDeltaT. The creating of this variable should be implemented

in solid/readSolidTimeControls.H.

3 A checking statement is written to check if the solidRegionDeltaT is

integral multiple of the deltaT. If not, the program will stop running instead of generating garbage results.

4 Based on the modification of step 3, in

chtMultiRegionMultiDeltaTFoam.C, Add #include <math.h> for the computation of the remainder between two floating numbers.

5 Modify the PIMPLE loop. 6 Run wmake in the top-level of the new solver.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The first approach

The modified PIMPLE loop

for (int oCorr=0; oCorr<nOuterCorr; oCorr++) { forAll(fluidRegions, i) { Info<< "\nSolving for fluid region "<< fluidRegions[i].name() << endl; #include "setRegionFluidFields.H" #include "readFluidMultiRegionPIMPLEControls.H" #include "solveFluid.H" } //To write the time variables in the log file. Info << "If statement remainder: " << fmod(runTime.value(), solidRegionDeltaT) << nl << "RunTime, solidDeltaT:" << nl << runTime.value() << ", " << solidRegionDeltaT << endl; //To check if the solid solver is to be run. if(fmod(runTime.value(), solidRegionDeltaT) < SMALL) { forAll(solidRegions, i) { Info<< "\nSolving for solid region " << solidRegions[i].name() << endl; #include "setRegionSolidFields.H" #include "readSolidMultiRegionPIMPLEControls.H" #include "solveSolid.H" } } } Yuzhu Pearl Li Implementation of multiple deltaTs based on chtMultiRegionFoam 2016-12-5 22 / 38

Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The first approach

The second approach

The second approach is to introduce two variables:

solidRegionDeltaTRef solidRegionRunTime Every time the runTime difference in equation (7) passes solidRegionDeltaTRef, the solid regions will be solved. runTime(i) − solidRegionRunTime(j-1) > solidRegionDeltaTRef (6) And then solidRegionRunTime(j) = runTime(i) (7)

The second approach will allow the adjustment of the time step.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The second approach

Second approach: implementation overview

1 Give the name to the new solver as

chtMultiRegionMultiDeltaTRefFoam.

2 Modifications in the Make/files. 3 Two new variables need to be created in

solid/readSolidTimeControls.H: solidRegionDeltaTRef and solidRegionRunTime.

4 Modify the PIMPLE loop in the main source file. 5 Compile the solver.

Detailed steps will be shown in the next slides.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The second approach

Implementation of multiple deltaTs to the multi-region solver

Give the name to the new solver as chtMultiRegionMultiDeltaTRefFoam.

mkdir -p $WM_PROJECT_USER_DIR/applications/solvers/multiphysics/ cd $WM_PROJECT_USER_DIR/applications/solvers/multiphysics/ cp -r $FOAM_SOLVERS/heatTransfer/chtMultiRegionFoam . mv chtMultiRegionFoam chtMultiRegionMultiDeltaTRefFoam cd chtMultiRegionMultiDeltaTRefFoam mv chtMultiRegionFoam.C chtMultiRegionMultiDeltaTRefFoam.C

Make sure that the binary file ends up in the user directory, following modifications need to be implemented in the make/files,

sed -i s/chtMultiRegionFoam/chtMultiRegionMultiDeltaTRefFoam/g Make/files sed -i s/FOAM_APPBIN/FOAM_USER_APPBIN/g Make/files

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The second approach

Implementation of multiple deltaTs to the multi-region solver

In solid/readSolidTimeControls.H.

vi solid/readSolidTimeControls.H

Add the following commands after the declaration of scalar maxDi:

scalar solidRegionDeltaTRef = runTime.controlDict(). lookupOrDefault<scalar>("solidRegionDeltaTRef", runTime.deltaT().value()); scalar solidRegionRunTime;

Add the Info statement also.

Info << "solidRegionDeltaTRef set to: " << solidRegionDeltaTRef << " s." << endl;

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The second approach

Implementation of multiple deltaTs to the multi-region solver

In chtMultiRegionMultiDeltaTRefFoam.C, before the line ’while (runTime.run())’, add solidRegionRunTime=0.0; Then, before ’runTime.write();’, replace the PIMPLE loop by the following codes (continue on the next page)

// --- PIMPLE loop for (int oCorr=0; oCorr<nOuterCorr; oCorr++) { forAll(fluidRegions, i) { Info<< "\nSolving for fluid region " << fluidRegions[i].name() << endl; #include "setRegionFluidFields.H" #include "readFluidMultiRegionPIMPLEControls.H" #include "solveFluid.H" } Yuzhu Pearl Li Implementation of multiple deltaTs based on chtMultiRegionFoam 2016-12-5 27 / 38

Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and The second approach

Implementation of multiple deltaTs to the multi-region solver

//To write the time step variables in the log file. Info << "RunTime-solidRegionRunTime: " << runTime.value()-solidRegionRunTime << nl << "RunTime, solidRegionRunTime, solidRegionDeltaTRef:" << nl << runTime.value() << ", " << solidRegionRunTime << ", " << solidRegionDeltaTRef << endl; //To check if the solid solver is to be run: if(runTime.value()-solidRegionRunTime > solidRegionDeltaTRef) { //set the solidRegionRunTime as current runTime and //store it in the variable for the next comparison solidRegionRunTime = runTime.value(); forAll(solidRegions, i) { Info<< "\nSolving for solid region " << solidRegions[i].name() << endl; #include "setRegionSolidFields.H" #include "readSolidMultiRegionPIMPLEControls.H" #include "solveSolid.H" } } }

Run wmake.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Try with the new solver

A quick hands-on: Try with the new solver:

Following the commands below to test the solver. Copy the tutorial case chtMultiRegionFoam/multiRegionHeater into run directory and rename it as multiRegionHeaterMultiDeltaTRef. f40NR mkdir -p $WM_PROJECT_USER_DIR/run/tutorials/test/chtMultiRegionFoam cd $WM_PROJECT_USER_DIR/run/tutorials/test/chtMultiRegionFoam cp -r $FOAM_TUTORIALS/heatTransfer/chtMultiRegionFoam/multiRegionHeater . mv multiRegionHeater multiRegionHeaterMultiDeltaTRef cd multiRegionHeaterMultiDeltaTRef In the system/controlDict, add the new created variable solidRegionDeltaTRef and set it to 0.01. Add the following line in to the controlDict file: solidRegionDeltaTRef 0.01; In the Allrun file, sed -i s/chtMultiRegionFoam/chtMultiRegionMultiDeltaTRefFoam/g Allrun

Then, type ./Allrun

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Verification and visualization

Verification

Check the log.chtMultiRegionMultiDeltaTRefFoam file. It shows that, the solid regions were run every time the RunTime-solidRegionRunTime is larger than 0.01. For example, at the first time step, the deltaT was adjusted to 0.101s, therefore, RunTime minus solidRegionRunTime was 0.101, larger than solidRegionDeltaTRef(0.01), so the solid regions were computed at this time step. deltaT = 0.1 Time = 0.101 Solving for fluid region bottomAir... Solving for fluid region topAir... RunTime-solidRegionRunTime: 0.101 RunTime, solidRegionRunTime, solidRegionDeltaTRef: 0.101, 0, 0.01 Solving for solid region heater... Solving for solid region leftSolid... Solving for solid region rightSolid...

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Verification and visualization

Visualization

To author’s knowledge, the multiRegionHeater tutorial case solved by chtMultiRegionFoam does not work well with paraview visualization in Foam-extend-4.0. Therefore, current way for solving such problem is to use paraview in OpenFOAM-4.0 instead. Open a new terminal, and source OpenFOAM-4.0 by: OF4x Then create files for each region for paraview post-processing by: touch multiRegionHeater{bottomAir}.OpenFOAM touch multiRegionHeater{heater}.OpenFOAM touch multiRegionHeater{leftSolid}.OpenFOAM touch multiRegionHeater{rightSolid}.OpenFOAM touch multiRegionHeater{topAir}.OpenFOAM Then paraview

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and Verification and visualization

Visualization

Meshes of the multiRegionHeater 3D view of multiRegionHeater Density of the topAir

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Pressure coupled boundary condition

A pressure coupled boundary condition for multi-physics solver was

• developed. It has not yet been applied into the solver at this stage.

solidWallPressureCoupled boundary condition was developed based on solidWallMixedTemperatureCoupled boundary condition. When pressure transfers from fluid to solid, it is only to do with the Dirichlet type boundary condition. Both sides agree on the pressure values: p1 = p2 (8) However, in the development, the Neumann type and Dirichlet-Neumann partitioning strategy is kept in case of future extension.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Pressure coupled boundary condition

The code of the new boundary condition solidWallPressureCoupled can be found in the attachments of this project. At current stage, the verification of such boundary condition cannot be done. To verify, more modifications to the solid solver need to be implemented.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Try with the Pressure coupled boundary condition

Replace the following condition in the field p in the tutorial case multiRegionHeater in Foam-extend-4.0, bottomAir_to_rightSolid { type buoyantPressure; value uniform 1e+05; } by bottomAir_to_rightSolid { type solidWallPressureCoupled; neighbourRegionName rightSolid; neighbourPatchName rightSolid_to_bottomAir; neighbourFieldName p; p p; value uniform 1e+05; }

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Try with the Pressure coupled boundary condition

However, after running, the case will stop with an error. It complains that: request for volScalarField p from objectRegistry rightSolid available objects of type volScalarField are 5 ( cp Kappa rho T rhosCps ) This is because a pressure field was not created for the solid regions. A volume field p needs to be created in order to use the pressure coupled boundary condition.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Summary and future work

The chtMultiRegionFoam has been studied and modified. The structure of the chtMultiRegionFoam solver was discussed. Two approaches of loop modifications were implemented and verified. A new boundary condition for pressure coupling was implemented. More work needs to be done:

The test and verification of the pressure coupled boundary condition. Solid solver modification for computing displacement and stress. Fluid solver modification for solving the incompressible two-phase fluids.

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Outline Introduction The chtMultiRegionFoam solver Loop modification Test the new solver Pressure coupled B.C. Summary and

Acknowledgement

I would like to thank Professor H˚ akan Nilson for providing the course of CFD with opensource software OpenFOAM and the continuous patience and support. Thanks to Gregor Cvijeti´ c for the technical help and very useful advices. Thanks to Turo V¨ alikangas for the knowledge sharing of the conjugate heat transfer solvers. I am immensely grateful to my supervisor Professor Muk Chen Ong from University of Stavanger. Many thanks to all the classmates in this course for we have shared a good time and knowledge with each other!

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