CEE 618 Scientific Parallel Computing (Lecture 10)

Transcription

1 1 / 20 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

2 2 / 20 Table of Contents 1 OpenFOAM: Overview 2 Mesh generation 3 Original tutorial case as it is Original tutorial case using parallel 4 Lab work

3 OpenFOAM: Overview Tool chain of Open-source CFD, OpenFOAM 3 / 20 In our case, blockmesh & gmsh OpenFOAM Paraview

4 OpenFOAM: Overview Specific Procedures 1 Mesh generation (gmsh) 1 Generate or modify geometry (.geo) file 2 Open geometry file and customize it if necessary 3 Generate mesh (.msh) file 2 OpenFOAM simulation 1 Convert.msh file (from gmsh) to OpenFOAM form using gmshtofoam 2 set boundary conditions 3 set initial conditions 4 adjust simulation parameters 5 run serial/parallel simulation using PBS 3 Paraview visualization 1 transfer compressed data file from server to your local computer 2 start Paraview and load.foam file (which has zero byte). 3 generate plots, e.g., color plot for pressure, vector plot for velocity vectors, and streamlines 4 / 20

5 5 / 20 gmsh tutorials Mesh generation 1 Manual 1 2 Gmsh tutorial 2 3 Gmsh-cavity tutorial

6 Original tutorial case as it is Simulation steps using cavity example 1 Log in fractal.eng.hawaii.edu using your private ssh-key. 2 Make OpenFOAM-Cases directory under your home dir.: $ mkdir OpenFOAM-Cases 3 Go to OpenFOAM-Cases and make/go to cavity dir.: $ cd OpenFOAM-Cases $ mkdir cavity $ cd cavity 4 Copy cavity files: $ cp -r /OpenFOAM/OpenFOAM-2.1.1/tutorials/incompressible/icoFoam/cavity/*./ 5 Run OpenFOAM simulation: (for large scale simulation, use PBS) $ touch cavity.foam $ blockmesh $ icofoam 6 Zip simulation directory to a file cavitydata.zip: $ cd.. $ zip -r cavitydata.zip cavity 6 / 20

7 7 / 20 blockmesh & icofoam Original tutorial case as it is 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, $ 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.

8 8 / 20 Before and After blockmesh Original tutorial case as it is

9 Original tutorial case as it is 9 / 20

10 10 / 20 running icofoam Original tutorial case as it is

11 11 / 20 Paraview-Visualization Original tutorial case as it is Figure: Pressure, velocity, and streamlines

12 Original tutorial case using parallel Parallel running of icofoam after blockmesh 1 Generate decomposepardict file under system. 2 numberofsubdomains = n x n y n z: 4 = We will use the simple method. delta is the cell skewed number, default= / * * C++ * * \ 2 ========= 3 \ \ / F i e l d OpenFOAM: The Open Source CFD Toolbox 4 \ \ / O p e r a t i o n Version : \ \ / A nd Web: org 6 \ \ / M a n i p u l a t i o n 7 \ * * / 8 FoamFile 9 { 10 version 2. 0 ; 11 format a s c i i ; 12 class dictionary ; 13 location " system " ; 14 object decomposepardict ; 15 } 16 / / * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * / / numberofsubdomains 4; method simple ; simplecoeffs 23 { 24 n ( ) ; 25 d e l t a 0.001; 26 } 12 / 20

13 13 / 20 Original tutorial case using parallel decomposepar mpirun reconstructpar

14 14 / 20 Original tutorial case using parallel decomposepar mpirun reconstructpar 1 Four directories are generated: processor0, processor1, processor2, and processor3.

15 15 / 20 Original tutorial case using parallel decomposepar mpirun reconstructpar 1 format: mpirunany.sh <Foam-Command> -parallel 2 PBS script is below. 1 #! / bin / bash 2 #PBS l w a l l t i m e =01:00:00 3 #PBS q batch 4 #PBS l nodes =04: ppn=1 5 #PBS N PRL icofoam 6 #PBS V 7 cd $PBS_O_WORKDIR 8 mpirunany. sh icofoam p a r a l l e l 3 Note that node=04 because numberofsubdomains=4 =

16 16 / 20 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: $ reconstructpar

17 17 / 20 Original tutorial case using parallel decomposepar mpirun reconstructpar Directories of 0.1,..., and 0.5 are reconstructed in the case directory.

18 18 / 20 Visualization Original tutorial case using parallel 1 Paraview visualization is same as the previous discussion. Figure: Pressure, velocity, and streamlines

19 19 / 20 OpenFOAM: dimension setting Original tutorial case using parallel 1 OpenFOAM dimension setting 4 2 Examples p dimensions [ ]: m 2 s 2 = m 2 /s 2 p = Force kg m s 2 = Area Density m 2 kg/m 3 = m2 s 2 U dimensions [ ]; m 1 s 1 = m/s nu [ ] 0.01; m 2 s 1 = m 2 /s ν=kinematic viscosity = absolute viscosity / density 4

20 Lab work Labwork: Non-cubic cavity 20 / 20 1 Use Gmsh to generate a mesh. You can edit.geo file for the cubic cavity, load it to gmsh, and generate a mesh. 2 Use OpenFoam for flow simulation. Run in (a) serial mode and (b) parallel mode using 4 (or more) processors. 3 Use Paraview for visualization and movie making.