Table of Contents. 1. OpenFOAM: Overview. 2. Mesh generation. 3. OpenFOAM
runs. Original tutorial case as it is. Original tutorial case using parallel. 4.
CEE 618 Scientific Parallel Computing (Lecture 10) Computational Fluid Mechanics using OpenFOAM: Cavity (2)
Albert S. Kim Department of Civil and Environmental Engineering University of Hawai‘i at Manoa 2540 Dole Street, Holmes 383, Honolulu, Hawaii 96822
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Table of Contents
1
OpenFOAM: Overview
2
Mesh generation
3
OpenFOAM runs Original tutorial case as it is Original tutorial case using parallel
4
Lab work
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OpenFOAM: Overview
Tool chain of Open-source CFD, OpenFOAM
In our case, blockMesh & gmsh → OpenFOAM → Paraview 3 / 20
OpenFOAM: Overview
Specific Procedures 1
Mesh generation (gmsh) 1 2 3
2
OpenFOAM simulation 1
2 3 4 5
3
Generate or modify geometry (.geo) file Open geometry file and customize it if necessary Generate mesh (.msh) file
Convert .msh file (from gmsh) to OpenFOAM form using gmshToFOAM set boundary conditions set initial conditions adjust simulation parameters run serial/parallel simulation using PBS
Paraview visualization 1 2 3
transfer compressed data file from server to your local computer start Paraview and load .foam file (which has zero byte). generate plots, e.g., color plot for pressure, vector plot for velocity vectors, and streamlines 4 / 20
Mesh generation
gmsh tutorials
1
Manual1
2
Gmsh tutorial2
3
Gmsh-cavity tutorial3
1 2 3
http://albertsk.files.wordpress.com/2011/12/gmsh.pdf http://albertsk.files.wordpress.com/2012/12/gmsh_tutorial.pdf http://albertsk.files.wordpress.com/2012/12/gmsh-cavity-tutorial.pdf 5 / 20
OpenFOAM runs
Original tutorial case as it is
Simulation steps using cavity example 1 2
3
4
Log in fractal.eng.hawaii.edu using your private ssh-key. Make OpenFOAM-Cases directory under your home dir.: $t mkdirt OpenFOAM-Cases Go to OpenFOAM-Cases and make/go to ‘cavity’ dir.: $t cdt OpenFOAM-Cases $t mkdirt cavity $t cdt cavity Copy cavity files: $t cpt -rt ˜ /OpenFOAM/OpenFOAM-2.1.1/tutorials/incompressible/icoFoam/cavity/*t ./
5
6
Run OpenFOAM simulation: (for large scale simulation, use PBS) $ touch cavity.foam $ blockMesh $ icoFoam Zip simulation directory to a file cavitydata.zip: $t cdt .. $t zipt -rt cavitydata.zipt cavity 6 / 20
OpenFOAM runs
Original tutorial case as it is
blockMesh & icoFoam 1
The mesh generator supplied with OpenFOAM, blockMesh, generates meshes from a description specified in an input dictionary, blockMeshDict located in the constant/polyMesh directory for a given case.
2
As ./constant/polyMesh/blockMeshDict exists, $t blockMesh
3
This will generate ’faces’, ’neighbour’, ’owner’, ’points’ under ./constant/polyMesh/.
4
Although blockMesh is a solid mesh generator, it is difficult for beginners.
5
Initially, the flow will be assumed laminar and will be solved on a uniform mesh using the icoFoam solver for laminar, isothermal, incompressible flow. 7 / 20
OpenFOAM runs
Original tutorial case as it is
Before and After ’blockMesh’
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OpenFOAM runs
Original tutorial case as it is
9 / 20
OpenFOAM runs
Original tutorial case as it is
running ’icoFoam’
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OpenFOAM runs
Original tutorial case as it is
Paraview-Visualization
Figure: Pressure, velocity, and streamlines
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OpenFOAM runs
Original tutorial case using parallel
Parallel running of ‘icoFoam’ after ‘blockMesh’ 1 2 3
Generate ‘decomposeParDict’ file under ‘system’. numberOfSubdomains = nx × ny × nz : 4 = 2 × 2 × 1 We will use the ‘simple’ method. ‘delta’ is the cell skewed number, default=0.001. http://www.openfoam.org/docs/user/running-applications-parallel.php#x12-820003.4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
/*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*− C++ −*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*\ | ========= | | | \\ / F ield | OpenFOAM : The Open Source CFD Toolbox | | \\ / O peration | Version : 2.1.1 | | \\ / A nd | Web: www. OpenFOAM . org | | \\/ M anipulation | | \*−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−*/ FoamFile { version 2.0; format ascii ; class dictionary ; location " system " ; object decomposeParDict ; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // numberOfSubdomains 4 ; method simpleCoeffs { n delta }
simple ;
( 2 2 1 ); 0.001; 12 / 20
OpenFOAM runs
Original tutorial case using parallel
decomposePar → mpirun → reconstructPar
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OpenFOAM runs
Original tutorial case using parallel
decomposePar → mpirun → reconstructPar 1
Four directories are generated: processor0, processor1, processor2, and processor3.
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OpenFOAM runs
Original tutorial case using parallel
decomposePar → mpirun → reconstructPar 1
format: mpirunany.sht t -parallel
2
PBS script is below.
1 2 3 4 5 6 7 8 3
# ! / b i n / bash #PBS − l w a l l t i m e =01:00:00 #PBS −q batch #PBS − l nodes =04: ppn=1 #PBS −N PRL−icoFoam #PBS −V cd $PBS_O_WORKDIR mpirunany . sh icoFoam − p a r a l l e l
Note that node=04 because numberOfSubdomains=4 = 2 × 2 × 1.
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OpenFOAM runs
Original tutorial case using parallel
decomposePar → mpirun → reconstructPar
After the parallel run is finished, under each of ‘processori’ directory, created directories are: 0, 0.1, 0.2, 0.3, 0.4, 0.5, and constant. Type/Enter: $t reconstructPar
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OpenFOAM runs
Original tutorial case using parallel
decomposePar → mpirun → reconstructPar
Directories of 0.1, ..., and 0.5 are ‘reconstructed’ in the case directory.
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OpenFOAM runs
Original tutorial case using parallel
Visualization 1
Paraview visualization is same as the previous discussion.
Figure: Pressure, velocity, and streamlines
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OpenFOAM runs
Original tutorial case using parallel
OpenFOAM: dimension setting 1
OpenFOAM dimension setting4
2
Examples p dimensions [0 2 -2 0 0 0 0]: m2 s−2 = m2 /s2 p=
Force kg m s−2 m2 = 2 = 2 3 Area × Density m kg/m s
U dimensions [0 1 -1 0 0 0 0]; m1 s−1 = m/s nu [ 0 2 -1 0 0 0 0 ] 0.01; m2 s−1 = m2 /s ν=kinematic viscosity = absolute viscosity / density 4
http://www.openfoam.org/docs/user/basic-file-format.php 19 / 20
Lab work
Labwork: Non-cubic cavity
1
2
3
Use Gmsh to generate a mesh. You can edit .geo file for the cubic cavity, load it to gmsh, and generate a mesh. Use OpenFoam for flow simulation. Run in (a) serial mode and (b) parallel mode using 4 (or more) processors. Use Paraview for visualization and movie making. 20 / 20
