[Haider-2018-OpenFOAM_course] OpenFOAM for beginners.pdf

Introduction Code Simulations Programming Tutorials Conclusions Appendix

OpenFOAM course for beginners:Hands-on training

Jibran Haider

Zienkiewicz Centre for Computational Engineering (ZCCE),College of Engineering, Swansea University, UK

https://www.jibranhaider.weebly.com

12 th September 2018

September 12, 2018Jibran Haider (PhD Computational Mechanics) OpenFOAM course for beginners 1

www.jibranhaider.weebly.com


Disclaimer

“This offering is not approved or endorsed by

OpenCFD Limited, producer and distributor of the

OpenFOAM software and owner of the

OPENFOAM R© and OpenCFD R© trade marks.”

Jibran Haider (PhD Computational Mechanics) OpenFOAM course for beginners 2


Outline

1 Introduction

2 The OpenFOAM code

3 OpenFOAM simulations

4 Programming in OpenFOAM

5 Hands-on training session

6 Conclusions

7 Appendix



Outline

1 IntroductionMy backgroundCourse detailsOpenFOAM preliminaries

2 The OpenFOAM code




6 Conclusions

7 Appendix



Outline


2 The OpenFOAM code




6 Conclusions

7 Appendix



Experience in computational mechanics

Year Topic Software Institution

[2009] CFD and experimental study of flow overcylindrical fins.

FLUENT NUST

[2012] Numerical simulation of sloshingphenomena in complex tanks.

FLOW-3D Universität Stuttgart & DLR

[2013]Modeling of phase change phenomenathrough a liquid-vapor interface inmicrogravity.

OpenFOAM Universität Stuttgart & DLR

[2014] A first order hyperbolic framework for largestrain fast solid dynamics.

OpenFOAM Swansea University & UPC



Outline


2 The OpenFOAM code




6 Conclusions

7 Appendix



Course details

Objectives

• Introduce the basics of OpenFOAM.

• Signify the advantages of using OpenFOAM.

• Utilise the power of Linux by extensive use of shell commands.

• By the end of the course, candidates should be able to run OpenFOAM simulations.

Desirable traits

• Basic level of programming in C++.

• Familiarization with Linux interface.

• Fundamentals of Computational Fluid Dynamics (CFD).

During this course we will be using

• OpenFOAM Foundation release (version 6).

• ParaView (version 5.4.0).



Outline


2 The OpenFOAM code




6 Conclusions

7 Appendix



What is OpenFOAM?

Summary

• An open source software package.

• Released under the GNU General Public License.

• Abbreviation of Open Field Operation And Manipulation.

• An efficient library of C++ modules.

• Based on the cell centered Finite Volume Method.

• Extensive CFD and Multi-physics capabilities.

• Cross-platform installation.

OpenFOAM forks

• OpenFOAM Foundation release (official standard release).

• OpenFOAM + (official development release).

• FOAM-extend (community driven development branch).

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This blog post [link] provides plenty of free references available on the web which might be a goodstarting point for learning OpenFOAM.


http://jibranhaider.weebly.com/blog/useful-references-for-openfoam-users


Key features of OpenFOAM

OpenFOAM is a C++ library of highest quality of programming for solving

computational continuum mechanics problems utilising all the features of

Objected Oriented Programming (OOP).

Key features of OOP

• Abstraction

• Inheritance

• PolymorphismObjects of different classes respond differently to functions of the same name.Also includes operator overloading.

Template metaprogramming

• C++ provides template classes.

• General features of the template class are passed on to any other class created from it.

• This reduces code duplication.



Why OpenFOAM?

OpenFOAMCommercial Software

(ANSYS, ABAQUS etc.)

1. Cost effectiveness X ×2. Parallel computing X X3. Source code X ×4. Redistribution of code X ×5. Collaborative development X ×6. Documentation × X7. GUI / user friendliness × X

X Motivates collaborative and project-driven development.

X According to the GNU GPL v3, OpenFOAM is free to download, install, use, modify and distribute.



Development of OpenFOAM

1989 Project was initially started under the title of FOAM at Imperial college, London.The idea was to create a simulation platform more powerful than FORTRAN. Dueto its object oriented features C++ was chosen as the programming language.

10th Dec 2004 OpenCFD Ltd was founded and first version (v1.0) of OpenFOAM was releasedunder the GNU GPL license.

8th Aug 2011 OpenCFD was acquired by Silicon Graphics International (SGI).

15th Aug 2012 OpenCFD became a wholly owned subsidiary of ESI group.

6th Aug 2018 OpenFOAM v6 was released.

Henry Weller and Hrvoje Jasak are the main initial contributors to its development.

Several developers from all over the globe have contributed to its development.

OPENFOAM R© is a registered trade mark of OpenCFD Limited, producer and distributor of theOpenFOAM software.



Simulation workflow

- blockMesh- snappyHexMesh

- Gmsh- Engrid

- Netgen- Tetgen

- SALOME - Blender

- ANSYS- Star-CCM+- SOLIDWORKS

Preprocessing Solver Postprocessing

- Incompressible- Compressible- Multiphase- Combustion- Heat transfer

- Molecular dynamics- Electromagnetics- Solid mechanics

- OpenFOAM utilities

- ParaView- OpenDX- SALOME

- VISIT- Netfabb- Gnuplot

- ANSYS- Tecplot- EnSight

- FieldView

OpenFOAM Other open source Commercial

- OpenFOAM utilities



Conventions used in this presentation

OpenFOAM terminologiesOpenFOAM_terminology

OpenFOAM command for applicationsOpenFOAM_application

Commands on terminal<< command_name



Environment variables & aliases

Environment variables are preconfigured to important OpenFOAM directories.

<< env | grep ˆFOAM_

FOAM_SOLVERS=/ opt / openfoam6 / a p p l i c a t i o n s / so lve rsFOAM_EXT_LIBBIN=/ opt / Th i rdPar ty −6/p la t fo rms / l inux64GccDPInt32 / l i bFOAM_APPBIN=/ opt / openfoam6 / p la t fo rms / l inux64GccDPInt32Opt / b inFOAM_TUTORIALS=/ opt / openfoam6 / t u t o r i a l s. . . . .

Aliases make use of environment variables to navigate inside OpenFOAM sources.

<< cat $WM_PROJECT_DIR/etc/config.sh/aliases

. . . . .62 a l i a s src= ’ cd $FOAM_SRC ’63 a l i a s l i b = ’ cd $FOAM_LIBBIN ’64 a l i a s app= ’ cd $FOAM_APP ’. . . . .



Outline

1 Introduction

2 The OpenFOAM codeCode structureApplicationsSolversUtilities




6 Conclusions

7 Appendix



Outline

1 Introduction





6 Conclusions

7 Appendix



Installation directory I

$WM_PROJECT_DIR

applications

solvers

test

utilities

tutorials

src

bin

doc

etc

platforms

wmake

1. applications:alias: app = ’cd $FOAM_APP’.This directory contains the source files of all theexecutables created using the C++ libraries. It containsthe following directories:

1.1 solvers:alias: sol = ’cd $FOAM_SOLVERS’.Source code to solve a particular continuummechanics problem.

1.2 test :Sample codes to help understand the usage ofOpenFOAM libraries.

1.3 Utilities:alias: util = ’cd $FOAM_UTILITIES’.Source code to perform pre- and post-processingtasks involving data manipulation and algebraicmanipulations.



Installation directory II

$WM_PROJECT_DIR

applications

tutorials

src

finiteVolume

OpenFOAM

turbulenceModels

. . .

bin

doc

etc

platforms

wmake

2. tutorials:alias: tut = ’cd $FOAM_TUTORIALS’.Contains tutorials that demonstrate the usage of allsolvers and most of the utilities.

3. src:alias: src = ’cd $FOAM_SRC’.It contains several subdirectories which include thesource code for all libraries. The important folders are:

3.1 finiteVolume:alias: foamfv = ’cd $FOAM_SRC/finiteVolume’.Includes classes for finite volume space/timediscretisation, boundary conditions etc.

3.2 OpenFOAM:This core library includes important definitions.

3.3 turbulenceModels:Contains libraries for turbulence models.



Installation directory III

$WM_PROJECT_DIR

applications

tutorials

src

bin

doc

etc

platforms

wmake

4. bin:This directory contains shell scripts such as paraFoam,foamLog etc.

5. doc:It contains all the documentation relevant to the version ofOpenFOAM including:5.1 User and Programmer’s guides5.2 Doxygen generated documentation5.3 OpenFOAM coding style guide

6. etc:It contains global OpenFOAM dictionaries and setup files.

7. platforms:The binaries generated during the compilation of theapplications and the dynamic libraries are stored here.

8. wmake:Compiler settings are included in this directory includingoptimisation flags. It also contains wmake, a special makecommand which understands the OpenFOAM file structure.



User’s working directory

The path to user’s working directory is stored in $WM_PROJECT_USER_DIR.

Check the path of working directory

<< echo $WM_PROJECT_USER_DIR

/ home / j i b r a n /OpenFOAM/ j i b r a n−6

Create the run directory

<< mkdir -p $FOAM_RUN

Check the path of ’run’ directory

<< echo $FOAM_RUN

/ home / j i b r a n /OpenFOAM/ j i b r a n −6/run



Outline

1 Introduction





6 Conclusions

7 Appendix



Directory structure

<application>

appName.C

*.H

Make

files

options

1. appName.C:Contains the main source code of the application.

2. *.H:The necessary header files needed to compile the application.The solvers include createFields.H file which declares andinitialises the field variables.

3. Make:This directory contains the compilation instructions andincludes the following files:

3.1 files:List of source files (*.C) needed to compile theapplication and the executable name.

3.2 options:Specifies the directories to search for the includedheader files (*.H) and libraries needed to link theapplication against.



Outline

1 Introduction





6 Conclusions

7 Appendix



OpenFOAM solvers I

X Over 70+ OpenFOAM solvers.

Basic CFD solvers

Solver Description

1. laplacianFoam Solves a Laplace equation.

2. potentialFoam Solves for potential flow.

Incompressible flow

Solver Description

1. icoFoam Transient solver for incompressible, laminar flow of Newtonian fluids.

2. simpleFoam Steady state solver for incompressible, turbulent flow.

3. pisoFoam Transient solver for incompressible flow.



OpenFOAM solvers II

Compressible flow

Solver Description

1. rhoCentralFoamDensity based compressible flow solver based on cen-tral upwind scheme.

2. sonicFoamTransient solver for trans-sonic/supersonic, laminar/tur-bulent flow of a compressible gas.

Multiphase flow

Solver Description

1. interFoamSolver for 2 incompressible, isothermal and immis-cible fluids based on the VOF method.

2. interPhaseChangeFoamSolver for 2 incompressible, isothermal and immis-cible fluids with a phase change model.

3. multiPhaseEulerFoamSolver for multiple compressible fluid phases withheat transfer.



OpenFOAM solvers III

Other solvers

Solver Description

1. solidDisplacementFoamTransient solver for linear-elastic, small-strain solver de-formation of a solid body.

2. mdFoam Molecular dynamics solver for fluids.

3. buoyantSimpleFoamSteady state solver for buoyant, turbulent flow of com-pressible fluids.

Solver names describe their functionality

simple: SIMPLE algorithm used in steady-state solvers.

piso: PISO algorithm used in transient solvers αCFL < 1.

pimple: PIMPLE algorithm used in transient solvers.

DyM: Supports dynamic mesh (eg. mesh refinement, moving meshes).



icoFoam solver

Main solver file<< find $FOAM_SOLVERS -name icoFoam.C | xargs cat -n

. . . . .27 Desc r i p t i on28 Trans ien t so l ve r for incompress ib le , laminar f low of Newtonian f l u i d s .. . . . .32 # inc lude " fvCFD .H" / / Header f i l e w i th a l l the FVM machinery33 # inc lude " p isoCon t ro l .H" / / F i l e s d e f i n i n g PISO c o n t r o l s. . . . .37 i n t main ( i n t argc , char ∗argv [ ] ) / / Beginning o f the main program38 39 # inc lude " setRootCase .H" / / Set path and case d i r e c t o r i e s40 # inc lude " createTime .H" / / I n i t i a l i s e t ime v a r i a b l e41 # inc lude " createMesh .H" / / I n i t i a l i s e the mesh to work w i th. . . . .52 while ( runTime . loop ( ) ) / / Time loop begins53 . . . . .115 runTime . w r i t e ( ) ; / / Wr i te r e s u l t s to t ime d i r e c t o r i e s. . . . .120 / / End t ime loop121122 In fo << "End \ n " << endl ;123124 return 0;125 . . . . .



Outline

1 Introduction





6 Conclusions

7 Appendix



OpenFOAM utilities I

X Over 80+ OpenFOAM utilities.

Mesh generation tools

Utility Description

1. blockMesh Multiblock mesh generator.

2. snappyHexMeshAutomatic split hexahedral mesher which refines and snaps tosurface producing hexahedral dominant cells.

Mesh conversion to OpenFOAM format

Utility Description

1. ansysToFoam ANSYS input mesh file exported from I-DEAS.

2. gambitToFoam GAMBIT mesh file.

3. gmshToFoam Reads .msh GMSH file.

4. ideasUnvToFoam I-DEAS unv format (eg. SALOME mesh).



OpenFOAM utilities II

Mesh manipulation tools

Utility Description

1. checkMesh Checks the quality of the mesh by providing a detailed output.2. renumberMesh Renumbers the cell list to reduce the bandwidth.3. refineMesh Refines mesh in multiple directions.4. autoRefineMesh Refines cells near to a surface.5. refineHexMesh Refines a hexahederal mesh by 2x2x2 cell splitting.

Post-processing tools

Utility Description

1. patchAverage Calculates average of a field over a patch.2. patchIntegrate Calculates integral of a field over a patch.3. probeLocations Outputs the field value at a particular location.4. foamCalc Utility for simple field calculations at specified times.5. writeCellCentres Output cell centres as a volScalarField.



OpenFOAM utilities III

Parallel processing tools

Utility Description

1. decomposeParDecomposes a mesh and fields of a case for parallelexecution.

2. reconstructParMeshReconstructs the decomposed mesh after parallel ex-ecution using only the geometric information.

Hands-on training:Some useful OpenFOAM utilities (See page 91)



Outline

1 Introduction

2 The OpenFOAM code

3 OpenFOAM simulationsTutorial directory structureMeshingProblem setupSolvingPost-processing



6 Conclusions

7 Appendix



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Tutorial directory structure I

<tutorial>

constant

polymesh

points

faces

owner

neighbour

boundary

... properties

system

0

1. constant :This directory contains the information which remains constantthroughout the simulation. It contains the following:

1.1 polymesh:Contains all the mesh information including:

(a) points → nodal positions

(b) faces → face connectivities

(c) owner → owner cell labels

(d) neighbour → neighbour cell labels

(e) boundary → boundary information

1.2 ... properties:Files which specify physical properties for a particularapplication eg. gravity, viscosity, thermal properties etc.



Tutorial directory structure II

<tutorial>

constant

system

controlDict

fvSchemes

fvSolution

0

p

U

2. system:This directory contains all the parameters associated with thesolution procedure. It contains at least the following files:

2.1 controlDict :Specifies the run control parameters such as start/endtime, time step, write interval etc.

2.2 fvSchemes:Contains the finite volume discretisation schemes usedfor the solution procedure such as spatial and temporaldiscretisations.

2.3 fvSolution:Contains equation solvers, algorithm controls andtolerances for the implicit solvers.

3. 0:The ’0’ directory corresponds to zero time. It contains theinitial and boundary conditions for variables (ie. pressure p,velocity U) in individual files.



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Meshing in OpenFOAM

• OpenFOAM only supports three dimensional meshes !!!

• 1D & 2D simulations are carried out by using appropriate ’empty ’ boundary conditions.

• Supports arbitrary polyhedral cells bounded by arbitrary polygonal faces.

Using blockMesh

• Simple mesh generator using blocks.

• Allows multiple blocks and curved edges.

• Not suitable to use for complex geometries.

Good practices

• Run ’checkMesh’ utility to monitor mesh quality.

• Check mesh in ParaView before starting the simulation using paraFoam command .

Hands-on training:

Meshing with blockMesh (See page 71)

Meshing with snappyHexMesh (See page 118)



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Selection of an appropriate OpenFOAM solver

Procedure

• Select an appropriate OpenFOAM solver (alias: sol) for the problem:<< ls $FOAM_SOLVERS

• Copy a suitable tutorial (alias: tut) to your run directory (alias: run).<< cp -r $FOAM_TUTORIALS/incompressible/icoFoam/cavity/cavity $FOAM_RUN

• Understand the inputs of the solver by reading the dictionaries of the tutorial.

• Modify the tutorial accordingly including geometry, meshing and problem setup.



OpenFOAM tutorial file syntax

A sub-dictionary is characterised by curly brackets ...

. . . . . / / Keyword e n t r i e s

A list is characterised by round brackets (...);

L i s t <Type> / / Type of l i s t<n> / / L i s t s i ze(. . . . . / / L i s t e n t r i e s) ;

A dimensionSet is characterised by square brackets [...]

[0 1 −1 0 0 0 0] / / [ Mass Length Time Temp. Quant i ty Current Luminos i ty ]



Initial conditions

Initial conditions must be specified for all variables inside ’0’ directory.

Standard initial conditions<< cat $FOAM_RUN/cavity/0/U

. . . . .17 dimensions [0 1 −1 0 0 0 0 ] ; / / Dimensions i n SI base u n i t s [ kg m s K mol A cd ]1819 i n t e r n a l F i e l d uni form (0 0 0) ; / / Ce l l values. . . . .

Non standard initial conditions

• setFields utility could also be utilised to initialise fields in OpenFOAM.

• The dictionary setFieldsDict provides the necessary inputs.

• funkySetFields utility of the swak4Foam library by B. Gschaider could also be utilised.

<< find $FOAM_TUTORIALS -name setFieldsDict



Boundary conditions I

• Boundary conditions must also be specified for all variables inside ’0’ directory.

• Geometry is broken down into patches where boundary conditions are applied.

Initial and boundary conditions<< cat $FOAM_RUN/cavity/0/U

. . . . .21 boundaryFie ld / / D i c t i o n a r y to spec i f y boundary cond i t i ons22 23 movingWall / / Boundary patch name24 25 type f ixedVa lue ; / / Boundary c o n d i t i o n type26 value uni form (1 0 0) ; / / Boundary values27 2829 f i xedWa l l s30 31 type noSl ip ;32 3334 frontAndBack35 36 type empty ; / / Boundary c o n d i t i o n type f o r 2D s imu la t i ons37 38 . . . . .



Boundary conditions II

Basic boundary conditions

BC type Data Example

1. fixedValue value U = (5, 10, 0)

2. fixedGradient gradient ∂T∂n = 3.5

3. zeroGradient _ ∂p∂n = 0

Non standard boundary conditions

• groovyBC library developed by B. Gschaider could be utilised without the need for programming.

• Custom boundary conditions can be programmed.



Time controls

controlDict dictionary<< cat $FOAM_RUN/cavity/system/controlDict

18 a p p l i c a t i o n icoFoam ; / / Name of so l ve r1920 star tFrom star tT ime ; / / Usefu l f o r r e s t a r t s imu la t i ons2122 s ta r tT ime 0; / / S t a r t i n g t ime2324 stopAt endTime ; / / Stopping c r i t e r i a2526 endTime 0 . 5 ; / / End t ime2728 de l taT 0.005; / / Time stepping ( De fau l t value o f 1 f o r steady s ta te so lve rs )2930 w r i t e C o n t r o l t imeStep ; / / C r i t e r i a f o r w r i t i n g r e s u l t s3132 w r i t e I n t e r v a l 20; / / I n t e r v a l f o r w r i t i n g r e s u l t s3334 purgeWri te 0 ; / / Disable r e w r i t i n g over t ime d i r e c t o r i e s3536 wr i teFormat a s c i i ; / / Format f o r w r i t i n g r e s u l t s3738 w r i t e P r e c i s i o n 6 ; / / P rec i s ion f o r w r i t i n g r e s u l t s3940 writeCompression o f f ; / / Disable compression f o r wr t i ng r e s u l t s4142 timeFormat general ; / / Format f o r w r i t i n g t ime d i r e c t o r i e s4344 t imePrec is ion 6 ; / / P rec i s ion f o r w r i t i n g t ime d i r e c t o r i e s4546 runTimeModi f iab le true ; / / Al lows m o d i f i c a t i o n o f s e t t i n g s dur ing the run



Solver controls I

fvSchemes dictionary<< cat $FOAM_RUN/cavity/system/fvSchemes

18 ddtSchemes19 20 defaul t Euler ; / / Time d i s c r e t i s a t i o n schemes21 23 gradSchemes / / Gradient eva lua t i on schemes24 25 defaul t Gauss l i n e a r ;26 grad ( p ) Gauss l i n e a r ;27 29 divSchemes / / D i s c r e t i s a t i o n o f the convect ive terms30 31 defaul t none ;32 d iv ( phi ,U) Gauss l i n e a r ;33 35 laplacianSchemes / / D i s c r e t i s a t i o n o f the Laplac ian term36 37 defaul t Gauss l i n e a r or thogonal ;38 40 in terpo la t ionSchemes / / Method of i n t e r p o l a t i o n41 42 defaul t l i n e a r ;43 45 snGradSchemes / / Surface normal g rad ien t scheme46 47 defaul t or thogonal ;48



Solver controls II

fvSolution dictionary<< cat $FOAM_RUN/cavity/system/fvSolution

18 so lve rs19 20 p21 22 so l ve r PCG; / / Solver to so lve the system23 p recond i t i one r DIC ; / / P recond i t i one r type24 to le rance 1e−06;25 r e l T o l 0 .05 ;26 28 pF ina l29 30 $p ;31 r e l T o l 0 ;32 34 U35 36 so l ve r smoothSolver ;37 smoother symGaussSeidel ;38 to le rance 1e−05;39 r e l T o l 0 ;40 41 4243 PISO / / PISO c o n t r o l s44 45 nCorrec tors 2 ;46 nNonOrthogonalCorrectors 0 ;. . . .49



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Running an OpenFOAM tutorial

Default procedure

• Copy OpenFOAM tutorial to you run directory.<< cp -r <tutorial_directory> $FOAM_RUN

<< cd <tutorial_name>

• Create mesh by using the blockMesh command.<< blockMesh

• Run simulation by using name of an OpenFOAM solver (eg. pisoFoam).<< pisoFoam

Procedure for complex tutorialsSome tutorials require an Allrun script to run and Allclean script to clear the tutorial directory.<< find $FOAM_TUTORIALS -name Allrun

Hands-on training:Two phase flow problem (See page 82)



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Post-processing OpenFOAM results

• OpenFOAM comes with builtin support for ParaView.

• ParaView is an open-source, multi-platform data analysis and visualisation application.

• Also possible to visualise OpenFOAM results with third-party applications.

• OpenFOAM results can be visualised using the paraFoam utility.<< paraFoam

ParaView toolbars

Main controls

Common filters

VCR controls Time controls

Active variable controls

Camera controls Axes control



Outline

1 Introduction

2 The OpenFOAM code


4 Programming in OpenFOAMOpenFOAM classesDimensional compatibilityMathematical operatorsMesh informationCode compilation


6 Conclusions

7 Appendix



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Basic classes

X Basic classes in OpenFOAM have been derived from more fundamental C++ classes.

X OpenFOAM classes are more advanced and have more functionality.

Some OpenFOAM classes

C++ class OpenFOAM class

1. int/long label

2. bool switch - Accepts true/false, on/off and yes/no.

3. string word

4. float/double scalar

5. — vector

6. — tensor - 3× 3 tensor with algebra



GeometricField class I

GeometricField class is templated around 3 arguments:

GeometricField < Type, PatchField, GeoMesh >

A ’Field ’ refers to a list of tensors along with a mesh.

• typedef is an alias for a class to improve readability.

• Used extensively in OpenFOAM particularly in relation to template classes.

The geometricField< Type > is renamed used typedef declarations to indicate where field variables arestored:

1. volField<Type> −→ Field defined at cell centres.

2. surfaceField<Type> −→ Field defined at cell faces.

3. pointField<Type> −→ Field defined at cell vertices.



GeometricField class II

(a) volField (b) surfaceField (c) pointField

Internal field:Defined at cell centersDefined at internal faces centersDefined at nodes

Boundary field:

Defined at boundary face centers



Equation mimicking

Classical incompressible Navier-Stokes equation

∂ρU∂t

+∇ · (ρUU)− µ∇2U = −∇p + b

Navier-Stokes equation in OpenFOAM

solve(

fvm : : ddt ( rho ,U)+ fvm : : d i v (U,U)− fvm : : l a p l a c i a n (mu,U)==− f vc : : grad ( p )+ b

) ;

1. typedef - fvm:

- Belongs the finiteVolumeMethod class.

- Performs an implicit evaluation and returns anfvMatrix .

2. typedef - fvc:

- Belongs to the finiteVolumeCalculus class.

- Performs an explicit calculation and returns ageometricField .



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Dimensional compatibility

X OpenFOAM is fully dimensional.

X Fields and properties have dimensions associated with them.

X Dimensional checking is performed to avoid meaningless operations.

X Units are defined using the dimensionSet class.

Dictionary in OpenFOAM

FoamFile

vers ion 2 . 0 ;format a s c i i ;class d i c t i o n a r y ;ob jec t t r a n s p o r t P r o p e r t i e s ;

/ / Thermal d i f f u s i v i t yDT DT [0 2 −1 0 0 0 0] 0 .01 ;

Sample OpenFOAM code

dimensionedTensor sigma(

" sigma " ,dimensionSet (1 ,−1 ,−2 ,0 ,0 ,0 ,0) ,tensor (1e6 ,0 ,0 ,0 ,10e6 ,0 ,0 ,0 ,5 e6 )

) ;



Standard dimensional units

QuantitySI Base Units

kg m s K mol A cd

1. Density 1 -3 0 0 0 0 0

2. Linear Momentum 1 -2 -1 0 0 0 0

3. Pressure 1 -1 -2 0 0 0 0

4. Force 1 1 -2 0 0 0 0

5. Lame’s Coefficients 1 -1 -2 0 0 0 0

6. Bulk Modulus 1 -1 -2 0 0 0 0

7. Young’s Modulus of Elasticity 1 -1 -2 0 0 0 0

8. Specific Heat Capacity 0 2 -2 -1 0 0 0

9. Thermal Conductivity 1 1 -3 -1 0 0 0



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Tensor operations

• Tensor operations available to all OpenFOAM tensor classes

Product operations

Product operator OpenFOAM notation Rank of a & b

1. Outer a ∗ b ≥ 12. Inner/dot a & b ≥ 13. Double inner/dot a && b ≥ 24. Cross aˆb = 1

Other operations

Product operator OpenFOAM notation

1. Magnitude mag (a)2. Square of magnitude magSqr (a)3. Square sqr (a)4. Power pow (a, n)



Tensor operations

Operations exclusive to tensors of rank 2

Operator OpenFOAM notation

1. Transpose A · T()

2. Diagonal diag (A)

3. Trace tr (A)

4. Symmetric part symm (A)

5. Skew-symmetric part skew (A)

6. Determinant det (A)

7. Cofactor cof (A)

8. Inverse inv (A)

Operations exclusive to tensors of rank 0

Operator OpenFOAM notation

1. Square root sqrt (s)

2. Exponential exp (s)

3. Natural log log (s)

4. Log base 10 log10 (s)

5. Sine sin (s)

6. Cosine cos (s)

7. Tangent tan (s)



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Mesh parameters

Important mesh parameters

Description Access function Data type

1. Total number of cells mesh.nCells() scalar

2. Total number of internal faces mesh.nInternalFaces() scalar

3. Cell volumes mesh.V() volScalarField

4. Face area normal vectors mesh.Sf() surfaceVectorField

5. Face area magnitudes mesh.magSf() surfaceVectorField

Coordinates

Coordinates Access function Data type

1. Cell center mesh.C() volVectorField2. Face center mesh.Cf() surfaceVectorField3. Nodal mesh.points() pointField

This blog post [link] contains useful mesh related information particularly mesh connectivities.


https://jibranhaider.weebly.com/blog/mesh-information-in-openfoam


Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



wmake compilation tool

X OpenFOAM uses its own compilation tool wmake.

X OpenFOAM applications and libraries require a Make directory.

X The Make directory contains the files and options files.

Make directories<< find $FOAM_SOLVERS -name Make | sort

<< cat -n$FOAM_TUTORIALS/stressAnalysis/solidEquilibriumDisplacementFoam/Make/files

<< cat -n$FOAM_TUTORIALS/stressAnalysis/solidEquilibriumDisplacementFoam/Make/options

CompilationThis is performed by executing the wmake command from the directory containing the Make folder.<< wmake



Outline

1 Introduction

2 The OpenFOAM code



5 Hands-on training sessionMeshing with blockMeshTwo-phase flow problemOpenFOAM utilitiesParallel computingSteady state flow problemMeshing with snappyHexMesh

6 Conclusions

7 Appendix



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Mesh creation using blockMesh utility

Find blockMesh files<< find $FOAM_TUTORIALS -name *blockMesh*

Arrange files according to size<< find $FOAM_TUTORIALS -name *blockMesh* | sort

Copy tutorial<< cp -r$FOAM_TUTORIALS/stressAnalysis/solidEquilibriumDisplacementFoam/beamEndLoad/$FOAM_RUN

<< cd $FOAM_RUN/beamEndLoad

<< tree

Generate mesh<< blockMesh | tee log.blockMesh

63 boundingBox : (0 0 0) (30 1 1)64 nPoints : 4265 nCel ls : 1266 nFaces : 5667 nIn terna lFaces : 16



Mesh quality using checkMesh utility

Check the mesh quality<< checkMesh > log.checkMesh

<< cat -n log.checkMesh

65 Checking geometry . . .66 Overa l l domain bounding box (0 0 0) (30 1 1)67 Mesh has 2 geometr ic ( non−empty / wedge ) d i r e c t i o n s (1 1 0)68 Mesh has 2 s o l u t i o n ( non−empty ) d i r e c t i o n s (1 1 0)69 A l l edges a l igned wi th or perpend icu la r to non−empty d i r e c t i o n s .70 Boundary openness (0 0 0) OK.71 Max c e l l openness = 0 OK.72 Max aspect r a t i o = 10 OK.73 Minimum face area = 0 . 5 . Maximum face area = 5. Face area magnitudes OK.74 Min volume = 2 . 5 . Max volume = 2 . 5 . To ta l volume = 30. Ce l l volumes OK.75 Mesh non−o r t h o g o n a l i t y Max : 0 average : 076 Non−o r t h o g o n a l i t y check OK.77 Face pyramids OK.78 Max skewness = 0 OK.79 Coupled po in t l o c a t i o n match ( average 0) OK.8081 Mesh OK.

Visualise the mesh<< paraFoam

Display the mesh using surface with edges option.



BlockMesh inputs I

Inputs for creating a mesh using blockMesh requires a blockMeshDict file

located in the system directory.

Study blockMeshDict file<< cat -n system/blockMeshDict

Modify blockMeshDict file to create a cube<< gedit system/blockMeshDict

17 convertToMeters 0.001; / / Sca l ing f o r convers ion to m i l l i m e t e r s

19 v e r t i c e s20 (21 (0 0 0) / / Vertex 022 (1 0 0) / / Vertex 123 (0 1 0) / / Vertex 224 (1 1 0) / / Vertex 325 (0 0 1) / / Vertex 426 (1 0 1) / / Vertex 527 (1 1 1) / / Vertex 628 (0 1 1) / / Vertex 729 ) ;

x

y

z0 1

2 3

4 5

67



BlockMesh inputs II

Defining cells

31 blocks32 (33 hex (0 1 3 2 4 5 6 7) / / Vertex l i s t f o r c rea t i on o f a hexahedral c e l l34 (5 5 5) / / No . o f c e l l s i n each d i r e c t i o n35 simpleGrading (1 .0 1.0 1 .0 ) / / Ce l l expansion r a t i o s36 ) ;

Ordering of vertices is critical when defining blocks!

33 hex ( 0 1 3 2 4 5 6 7 )

Plane 1 Plane 2

xyz

x

y

z0 1

2 3

4 5

67

Delete unused entries

38 edges39 (40 ) ;

81 mergePatchPairs82 (83 ) ;



BlockMesh inputs III

Modify boundary definition

38 boundary / / Contains d e f i n i t i o n o f boundary patches39 (40 s ides / / Boundary patch name41 42 type patch ;43 faces44 (45 (4 0 2 7) / / Boundary face d e f i n i t i o n s46 (1 5 6 3)47 (0 1 3 2)48 (4 5 6 7)49 ) ;50 51 bottom52 53 type patch ;54 faces55 (56 (0 1 5 4)57 ) ;58 59 top60 61 type patch ;62 faces63 (64 (2 3 6 7)65 ) ;66 67 ) ;



blockMesh and checkMesh utilities

Generate mesh<< blockMesh > log.blockMesh

<< cat -n log.blockMesh

61 boundingBox : (0 0 0) (0.001 0.001 0.001)62 nPoints : 21663 nCel ls : 12564 nFaces : 45065 nIn terna lFaces : 300

Check the mesh quality<< checkMesh > log.checkMesh

<< cat -n log.checkMesh

62 Checking geometry . . .66 Boundary openness (9.485e−17 9.485e−17 5.9557e−17) OK.67 Max c e l l openness = 8.27181e−17 OK.68 Max aspect r a t i o = 1 OK.69 Minimum face area = 4e−08. Maximum face area = 4e−08. Face area magnitudes OK.70 Min volume = 8e−12. Max volume = 8e−12. To ta l volume = 1e−09. Ce l l volumes OK.71 Mesh non−o r t h o g o n a l i t y Max : 0 average : 072 Non−o r t h o g o n a l i t y check OK.73 Face pyramids OK.74 Max skewness = 3.68629e−15 OK.75 Coupled po in t l o c a t i o n match ( average 0) OK.7677 Mesh OK.



Post-processing with paraFoam utility

Visualise (or try to visualise) the mesh<< paraFoam

−−> FOAM FATAL IO ERROR:Cannot f i n d pa tchF ie ld en t ry for s ides

f i l e : / home / j i b r a n /OpenFOAM/ j i b r a n −6/run / beamEndLoad / 0 / p . boundaryFie ld from l i n e 25 to l i n e 49.

From f u n c t i o n void Foam : : Geometr icField <Type , PatchFie ld , GeoMesh> : : Boundary : : readF ie ld ( constFoam : : DimensionedField <TypeR , GeoMesh>&, const Foam : : d i c t i o n a r y &) [ w i th Type = double ; PatchFie ld= Foam : : f vPa tchF ie ld ; GeoMesh = Foam : : volMesh ]

i n f i l e / home / ubuntu /OpenFOAM/OpenFOAM−6/src /OpenFOAM/ l n I n c l u d e / Geometr icBoundaryField .C at l i n e 191.

FOAM e x i t i n g

Delete 0 directory<< rm -r 0

Visualise the mesh<< paraFoam

Display the mesh using surface with edges option.



Exercise I: Meshing with blockMesh I

Increase the mesh density to 10×10×10 cells.

Hint

• You can edit the blockMeshDict file using your favourite text editor (eg. vi, gedit, nano).

<< vi system/blockMeshDict



Exercise I: Meshing with blockMesh II

Connect points 6 and 3 with an arc instead of a line.

Add the following after the blocks definition

38 edges39 (40 arc 6 3 (1 .3 1.3 0 .5 )41 ) ;

x

y

z0 1

2 3

4 5

67



What have we learnt in this tutorial?

X Mesh generation using blockMesh utility.

X Understand the structure of blockMeshDict file.

X Modify blockMeshDict file to our requirements.

X Determine the quality of mesh with checkMesh utility.

X Visualise the mesh with paraFoam utility.

X Understand OpenFOAM error messages displayed on the terminal.

X Use of tee command to simultaneously display and write output to a file.

X Use of the standard output stream < to redirect output to a file.

X Use of cat command to print and vi to modify contents of a file.



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Breaking of a dam

Simulate breaking of a dam using the two-phase flow solver in OpenFOAM.

The interFoam solver is based on the Volume Of Fluid interface capturing approach.

Problem description

• Transient two phase flow

• Incompressible, isothermal flow

• Immiscible fluids 0.292 m

0.584 m

0.584 m

0.1461 m 0.1459 m

0.024 m

0.048 m

WaterColumn

Air



interFoam solver

Description of solver<< find $FOAM_SOLVERS -name interFoam.C | xargs cat -n | sed -n"/Description/,/*/p"

27 Desc r i p t i on28 Solver for 2 incompressib le , i so therma l immisc ib le f l u i d s using a VOF29 ( volume of f l u i d ) phase−f r a c t i o n based i n t e r f a c e cap tu r ing approach ,30 wi th o p t i o n a l mesh motion and mesh topology changes i n c l u d i n g adapt ive31 re−meshing .

Find solver location<< locate interFoam.C

/ opt / openfoam6 / a p p l i c a t i o n s / so lve rs / mul t iphase / interFoam / interFoam .C

Copy damBreak tutorial<< cp -r $FOAM_TUTORIALS/multiphase/interFoam/laminar/damBreak/damBreak/$FOAM_RUN



interFoam solver

Change to damBreak directory<< cd $FOAM_RUN/damBreak

Study contents of tutorial<< tree

Generate mesh and view in ParaView<< blockMesh

<< checkMesh

<< paraFoam

Solve and view results<< interFoam

<< paraFoam

Display the mesh using surface with edges option.Select phase fraction (alpha.water) field to display.



Check problem setup

Initial phase fraction field<< cat 0/alpha.water.orig

19 i n t e r n a l F i e l d uni form 0;

Study contents of tutorial<< tree system

system|− blockMeshDict|− c o n t r o l D i c t|− decomposeParDict|− fvSchemes|− f v S o l u t i o n|− s e t F i e l d s D i c t

Description of setFields utility<< find $FOAM_UTILITIES -name setFields.C | xargs cat -n | sed -n"/Description/,/*/p"

24 Desc r i p t i on25 Set values on a se lec ted set o f c e l l s / patchfaces through a d i c t i o n a r y .



Initialise fields

Display contents of setFieldsDict<< cat -n system/setFieldsDict

18 de fau l tF ie l dVa lues19 (20 vo lSca la rF ie ldVa lue alpha . water 021 ) ;2223 reg ions24 (25 boxToCell26 27 box (0 0 −1) (0.1461 0.292 1) ;28 f i e l d V a l u e s29 (30 vo lSca la rF ie ldVa lue alpha . water 131 ) ;32 33 ) ;

Run setFieldsDict utility<< setFields

<< tree 0

<< head -50 0/alpha.water



Solution

Run the solver again<< interFoam

<< paraFoam

t = 0.0 s

t = 0.15 s t = 0.30 s t = 1.0 s



Exercise II: Breaking of a dam

Simulate the same scenario but with a refined mesh and save an animation.

Hint

• A utility "refineMesh" could be utilised.

• Time directories can be removed with << foamListTimes -rm.

• Please pay attention to the error messages displayed on your terminal.The solution is always there!!!

t = 0.15 s t = 0.30 s t = 1.0 s




X Running an OpenFOAM solver.

X Use find command to search description of OpenFOAM solvers and utilities.

X Use setFields utility to initialise fields.

X Output OpenFOAM solver data to a log file.

X Use refineMesh utility to increase mesh density.

X Understand OpenFOAM errors displayed on the terminal.

X Clear tutorial time directories with foamListTimes -rm.



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



In this tutorial we will learn about the usage of some useful

OpenFOAM utilities.



Alternative mesh formats I

How to use a mesh generated from ANSYS FLUENT for OpenFOAM simulations?

Search for a fluent mesh tutorial<< grep -r fluent $FOAM_TUTORIALS

/ opt / openfoam6 / t u t o r i a l s / incompress ib le / icoFoam / elbow / A l l r u n : r unApp l i ca t i on fluentMeshToFoam elbow .msh/ opt / openfoam6 / t u t o r i a l s / incompress ib le / icoFoam / elbow / A l l c l e a n : rm −r f f l u e n t I n t e r f a c e

Copy ’elbow’ tutorial<< cp -r $FOAM_TUTORIALS/incompressible/icoFoam/elbow/ $FOAM_RUN

<< cd $FOAM_RUN/elbow

<< tree

Convert FLUENT mesh to OpenFOAM format<< fluentMeshToFoam elbow.msh

<< checkMesh

<< paraFoam



Alternative mesh formats II

Other supported mesh formats<< ls $FOAM_UTILITIES/mesh/conversion

ansysToFoam foamMeshToFluent ideasUnvToFoam plot3dToFoam vtkUnstructuredToFoamcfx4ToFoam foamToStarMesh kivaToFoam sammToFoam writeMeshObjdatToFoam foamToSurface mshToFoam star3ToFoamfluent3DMeshToFoam gambitToFoam netgenNeutralToFoam star4ToFoamfluentMeshToFoam gmshToFoam Opt iona l tetgenToFoam



Cell labels

Convert to ParaView’s VTK format<< foamToVTK

<< tree

Read mesh in paraview<< paraview

File −→ Open −→ ’VTK/elbow_0.vtk’.Display the mesh using surface with edges.Color by cell ID.

X High bandwidth slows the performance of matrix solvers.

X Renumbering of cell labels can reduce the bandwidth in a solution matrix.



Renumber cell labels

Use ’renumberMesh’ utility<< renumberMesh

Mesh s ize : 918Before renumbering :

band : 735p r o f i l e : 103613

A f t e r renumbering :band : 29p r o f i l e : 11753

Wr i t i ng mesh to " 0.05 "

<< tree

VTK|− elbow_0 . v tk|− elbow_1 . v tk

Renumber cells<< renumberMesh -help

−ove rwr i t e ove rwr i t e e x i s t i n g mesh / r e s u l t s f i l e s



Visualise results

Display new cell labels<< foamToVTK

<< paraview&

File −→ Open −→ "VTK/elbow_1.vtk"Display the mesh using surface with edges and color by cell ID.

(a) Before (b) After




X Convert mesh from FLUENT to OpenFOAM compatible format using thefluentMeshToFoam utility.

X Convert mesh from OpenFOAM to VTK format using the foamToVTK utility.

X Use renumberMesh utility to decrease bandwidth.

X Search for a particular text using ‘grep’ command.

X See usage of an OpenFOAM command using ‘-help’ option.



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Compare the performance of a parallel run against a serial run

in OpenFOAM.



Problem setup

Copy damBreak tutorial<< run

<< cp -r $FOAM_TUTORIALS/multiphase/interFoam/laminar/damBreak/damBreak/ .

Refine the mesh for better comparison of run times for serial and parallel simulations

Mesh refinement<< mv damBreak damBreakFine_serial

<< cd damBreakFine_serial

<< gedit system/blockMeshDict

47 blocks48 (49 hex (0 1 5 4 12 13 17 16) (70 15 1) simpleGrading (1 1 1)50 hex (2 3 7 6 14 15 19 18) (60 15 1) simpleGrading (1 1 1)51 hex (4 5 9 8 16 17 21 20) (70 120 1) simpleGrading (1 2 1)52 hex (5 6 10 9 17 18 22 21) (8 120 1) simpleGrading (1 2 1)53 hex (6 7 11 10 18 19 23 22) (60 120 1) simpleGrading (1 2 1)54 ) ;

<< blockMesh



Serial run

Check mesh<< checkMesh

Overa l l number o f c e l l s o f each type :hexahedra : 18510

<< paraFoam

Duplicate case setup for parallel run<< cp -r $FOAM_RUN/damBreakFine_serial $FOAM_RUN/damBreakFine_parallel

Run the problem<< setFields

<< interFoam | tee log.serial

ExecutionTime = 330.7 s ClockTime = 331 s

Visualise results<< paraFoam



Domain decomposition I

• OpenFOAM uses domain decomposition for parallel runs.

• Geometry is broken down and allocated to separate processors.

• Decomposition requires a system/decomposeParDict file.

• Decomposition process is initiated by using the decomposePar utility.



Domain decomposition II

Check contents of decomposeParDict<< cd $FOAM_RUN/damBreakFine_parallel

<< cat -n system/decomposeParDict

18 numberOfSubdomains 4 ; / / No . o f subdomains f o r decomposit ion1920 method simple ; / / Method of decomposit ion2122 simpleCoef fs / / C o e f f i c i e n t s f o r s imple method23 24 n (2 2 1) ; / / Domain s p l i t i n x , y , z d i r e c t i o n s25 de l t a 0 .001; / / Ce l l skew f a c t o r ( De fau l t value = 0.001)26 2728 h i e r a r c h i c a l C o e f f s / / C o e f f i c i e n t s f o r h i e r a r c h i c a l method29 30 n (1 1 1) ;31 de l t a 0 .001;32 order xyz ; / / Order i n which the decomposit ion i s done33 3435 manualCoeffs36 37 da taF i l e " " ;38 3940 d i s t r i b u t e d no ; / / I f data i s d i s t r i b u t e d over severa l d isks4142 roo ts ( ) ;



Domain decomposition III

Find available processors<< nproc -all

16

Modify decomposeParDict if necessary<< gedit system/decomposeParDict

Modify the ’numberOfSubdomains’ and the domain split ’n’ accordingly:

18 numberOfSubdomains 9 ; / / No . o f subdomains f o r decomposit ion1920 method simple ; / / Method of decomposit ion2122 simpleCoef fs / / C o e f f i c i e n t s f o r s imple method23 24 n (3 3 1) ; / / Domain s p l i t i n x , y , z d i r e c t i o n s25 de l t a 0 .001; / / Ce l l skew f a c t o r ( De fau l t value = 0.001)26

Some decomposition methodologies1. simple −→ Used for simple geometries by using geometric decomposition.2. hierarchical −→ Similar to simple but with order of direction split.3. scotch −→ Used for complex geometries by minimising the number of processor boundaries.4. manual −→ User specified decomposition for each cell.



Domain decomposition IV

Initialise the problem<< blockMesh

<< setFields

<< checkMesh

Decompose domain for parallel execution<< decomposePar

<< tree

<< paraFoam -case processor0

(a) Processor 0 (b) Processor 1



Parallel run

• OpenFOAM uses the public domain openMPI implementation of the standardMessage Passing Interface (MPI).

• Syntax for parallel execution on a single node is as follows:<< mpirun -np <no_of_processors> <solver_name> -parallel

Parallel run<< foamJob -parallel -screen interFoam

<< gnome-system-monitor

Visualise results<< ls

<< tree processor0

<< paraFoam -case processor0

Simulation time for parallel run<< tail log



Reconstruct solution

reconstructPar utility can be used to reassemble the fields and mesh from thedecomposed parallel run.

Reconstruction of results<< reconstructPar

Visualise results<< ls

<< paraFoam



Exercise III: Parallel performance

Analyse parallel performance of the interFoam solver.

Clean script<< find $FOAM_TUTORIALS -name Allclean | sort

<< cp$FOAM_TUTORIALS/stressAnalysis/solidDisplacementFoam/plateHole/Allclean .

<< ./Allclean

Parallel speedup

Speedup ratio =Tserial

Tparallel

No. of processors Simulation time (s) Speedup

1. 1 ≈ 330 —–

2. 4 ≈ 108 3.055

3. 9 ≈ 80 4.125




X Setup decomposeParDict with appropriate number of processors.

X Use decomposePar utility to decompose to domain.

X Launch a parallel run on a single node using mpirun with ’-parallel’ option.

X Use reconstructPar utility to reassemble decomposed fields and mesh.



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Exercise IV: Selection of an OpenFOAM solver

Simulate the problem using an appropriate OpenFOAM solver.

Problem description

• Two dimensional, steady state flow.

• Incompressible and turbulent flow.

• Newtonion fluid with viscosity ν = 1× 10−5m2/s.

Case setup

InletU = 10 m/s

Oulet

p = 0 Pa

∂U∂n = 0

WallU = 0 m/s

2.06 m 0.84 m0.206 m

0.508 m 0.332 m




Hints

• Choose a relevant OpenFOAM solver.

• Select an appropriate tutorial as a starting point.

• Don’t start writing input files from scratch.

• Please pay attention to the error messages displayed on your terminal.

• Remember to define the problem variables correctly.

Geometry and meshing




Pressure distribution

Velocity vectors




Increase the initial velocity to [10, 10, 0] m/s

Velocity vectors




X Select an OpenFOAM solver based on the problem definition.

X Understand additional OpenFOAM errors displayed on the terminal.

X Modify parameters in the input files according to our needs.

X Create input files by copying an already existing similar file.

X Use the glyph filter in ParaView to plot vectors.



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Basics of snappyHexMesh I

Steps for creating a snappyHexMesh

1. Creation of a castellated mesh

(a) Background mesh (b) Refinement initiated

(c) Refinement completed (d) Cell removal



Basics of snappyHexMesh II

2. Snap to surface

(e) Region refinement (f) Snapping

3. Addition of layers

(g) Layer addition



Surface meshes I

Copy the motorbike tutorial<< run

<< cp -r $FOAM_TUTORIALS/incompressible/simpleFoam/motorBike .

<< cd motorike

<< tree constant

Obtain motorbike geometry<< cp $FOAM_TUTORIALS/resources/geometry/motorBike.obj.gzconstant/triSurface

<< gunzip motorBike.obj.gz

Visualise geometry<< paraview

File −→ Open −→ "constant/triSurface/motorBike.obj"Display surface with edges.



Surface meshes II

OpenFOAM utilities for surfaces<< surface[TAB][TAB]

surfaceAdd sur faceFea tu reEx t rac t surfaceMeshExport sur faceSp l i tByPatchsurfaceAutoPatch sur faceFeatures surfaceMeshImport sur faceSpl i tByTopo logysurfaceBooleanFeatures sur faceFind surfaceMeshInfo sur faceSp l i tNonMan i fo ldssurfaceCheck surfaceHookUp surfaceMeshTr iangulate surfaceSubsetsurfaceClean s u r f a c e I n e r t i a su r faceOr ien t surfaceToPatchsurfaceCoarsen surfaceLambdaMuSmooth surfacePointMerge sur faceTransformPointssur faceConver t surfaceMeshConvert su r faceRed is t r i bu teParsur faceFeatureConver t surfaceMeshConvertTest ing surfaceRefineRedGreen

Surface mesh information<< surfaceMeshInfo -help

<< surfaceMeshInfo constant/triSurface/motorBike.obj

nPoints : 132871nFaces : 331653area : 12.1486



Surface meshes III

Extract surface features from the geometry<< surfaceFeatureExtract

<< tree

View patches<< surfaceConvert constant/triSurface/motorBike.objconstant/triSurface/motorBike.vtk

<< paraview

File −→ Open −→ "constant/triSurface/motorBike.vtk"Display region.



Castellated mesh I

Meshing using snappyHexMesh utility requires a base background mesh to start with.

Notes

• Must only consist of hexahedral cells.

• The aspect ratio of cells should be close to 1 for optimal snapping process.

Create background mesh<< blockMesh



Castellated mesh II

Run snappyHexMesh in parallel<< decomposePar

<< foamJob -parallel -screen snappyHexMesh

<< less system/snappyHexMeshDict

Local mesh refinement

(a) Level 0 (b) Level 1 (c) Level 2 (d) Level 4

Reconstruct decomposed mesh<< reconstructParMesh -time 1

<< checkMesh

<< tree



Castellated mesh III



Snapping I

Cell faces are projected down onto the surface geometry.



Snapping II

Check the quality of snapping process.



Exercise V: Run motorBike tutorial I

• Clean tutorial: << ./Allclean

• Run tutorial: << ./Allrun



Exercise V: Run motorBike tutorial II



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



What have we learnt in this course?

Commands

X Effective usage of bash shell commands.

X Navigate through important directories by using environment variables and aliases.

Basics of OpenFOAM

X Understand the organisation of OpenFOAM installation directory structure.

X Understand the tutorial directory structure of OpenFOAM.

X A brief introduction to programming in OpenFOAM.



What have we learnt in this course?

Meshing

X Use blockMesh utility to generate simple meshes.

X Use snappyHexMesh utility for generating complex meshes.

X Use mesh conversion utilities in OpenFOAM to use meshes from external software.

Solving

X Use OpenFOAM solvers to run simulations.

X Use various OpenFOAM utilities for parallel simulations.

Visualising

X Use ParaView for post-processing results.



Outline

1 Introduction

2 The OpenFOAM code




6 Conclusions

7 Appendix



Basic Linux commands I

• cd <directory>

Change to a directory location.

• cd

Change to the home directory.

• cd ..

Go one level up from current directory.

• cd ../..

Go two levels up from current directory.

• mkdir <directory>

Create a directory.

• rm -r <directory>

Remove directory with all its contents.

• pwd

Print the present working directory path.

• ls <directory>

List contents of a directory.

• tree

Print the current directory structure.

• clear

Clears the terminal window.

• ps / topDisplays information about current runningprocesses.

• kill <PID>

Kills a process ID.

• <command> -help

See help for a particular command.

• man <command>

Manual for a particular command, press ’q’to quit.



Basic Linux commands II

• cp <directory1> <directory2>

Copy a directory from directory path 1 to 2.

• mv <file1> <file2>

Rename file1 to file2.

• vi <file>

Open a text file, press ’:i’ to insert text, ’:w’ to save, ’:q’ to quit, ’SHIFT+zz’ to save and quit.

• cat <file>

Print contents of the file..

• head -10 <file>

Print first 10 lines of a file.

• tail -50 <file>

Print last 50 lines of a file.



Useful Linux commands for OpenFOAM

• blockMesh -help

See usage of an OpenFOAM command.

• find $FOAM_TUTORIALS -name sampleDict

Search sampleDict file in ’$FOAM_TUTORIALS’ directory.

• find $FOAM_SRC -type f | xargs grep -l "::findNearestCell"

Search the definition of ’findNearestCell’ function in ’$FOAM_SRC’ directory.

• find $FOAM_SRC -type l | xargs grep -l typedef | xargs grep -l"volScalarField;"

Find the typedef , ’volScalarField ’ in ’$FOAM_SRC’ directory.

• find $FOAM_SOLVERS -name "*FvPatch*"

Find solver specific boundary conditions in ’$FOAM_SOLVERS’ directory.

• find $FOAM_SOLVERS -name *.C | xargs grep -l incompressible | xargs grep -lmultiphase

Find ’*.C’ files in ’$FOAM_SOLVERS’ directory which contain the words ’incompressible’ and’multiphase’.


[Haider-2018-OpenFOAM_course] OpenFOAM for beginners.pdf

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Transcript of [Haider-2018-OpenFOAM_course] OpenFOAM for beginners.pdf