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July 27, 2009, 00:04 |
Inviscid Supersonic Flow Simulation
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#1 |
New Member
Alan Harrland
Join Date: Mar 2009
Posts: 21
Rep Power: 17 |
Hi everyone.
I am currently undertaking a Phd in hypersonics, and I am required to perform some supersonic CFD simulations in OpenFOAM. I am quite new to this, so I have a few (and I am sure I will have plenty more) questions. Initially I am simulating a wedge in a supersonic flow. I have based my initial model on the wedge15Ma5 tutorial case in rhopSonicFoam. My first question is when playing around with the wedge tutorial, if I increase the Mach number the solution rapidly diverges (courant number increases exponentially until the solver crashes). I altered the mach number in the 0/U file (changed it from 5 to 10, and also tried other values in between this range). Any ideas why this is happening? My second question is what are the differences between rhoSonicFoam and rhopSonicFoam? I know that rhop is density pressure solver, but what does this mean? Am I using the right solvers in this case? What are their limitations etc? If anyone could point me in the right direction as to where I could find this information, that would be great. Thanks, Alan. |
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July 27, 2009, 04:08 |
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#2 | |||
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36 |
Quote:
Did you reduce the time step or enable the automatic time stepping to respect the CFL condition? I run it with Co = 1. However for better results stay under 0.5. Quote:
You might want to consider also rhoCentralFoam, which is based on a Riemann-free type of scheme developed by Turganov and Tadmor (the reference to the paper is in the code). I tried it on the same tutorial, and with the same changes I suggested above it runs OK. Quote:
Best,
__________________
Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. |
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July 27, 2009, 04:36 |
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#3 |
New Member
Alan Harrland
Join Date: Mar 2009
Posts: 21
Rep Power: 17 |
Thanks Alberto, I had tried adjusting the time step, but it still diverged. Now that I have put adaptive time step on, it doesn't diverge. Thanks again for that.
I'm having a bit of trouble with a mesh I am generating based on this tutorial. I am essentially trying to model a cone in a supersonic flow. My blockMeshDict file is: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 1.5 | | \\ / A nd | Web: http://www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 1; vertices ( (0 0 -0.05) (1 0 -0.05) (1.5 0 -0.05) (3 0 -0.05) (1 0.85 -0.05) (1.5 0.85 -0.05) (1 1 -0.05) (1 1.15 -0.05) (1.5 1.15 -0.05) (0 2 -0.05) (1 2 -0.05) (1.5 2 -0.05) (3 2 -0.05) (3 0.85 -0.05) (3 1.15 -0.05) (0 0 0.05) (1 0 0.05) (1.5 0 0.05) (3 0 0.05) (1 0.85 0.05) (1.5 0.85 0.05) (1 1 0.05) (1 1.15 0.05) (1.5 1.15 0.05) (0 2 0.05) (1 2 0.05) (1.5 2 0.05) (3 2 0.05) (3 0.85 0.05) (3 1.15 0.05) ); blocks ( hex (0 1 10 9 15 16 25 24) (100 200 1) simpleGrading (1 1 1) hex (1 2 5 4 16 17 20 19) (50 85 1) simpleGrading (1 1 1) prism (8 7 6 23 22 21) (50 15 1) simpleGrading (1 1 1) prism (6 4 5 21 19 20) (50 15 1) simpleGrading (1 1 1) hex (7 8 11 10 22 23 26 25) (50 85 1) simpleGrading (1 1 1) hex (2 3 14 5 17 18 29 20) (150 85 1) simpleGrading (1 1 1) hex (5 14 13 8 20 29 28 23) (150 30 1) simpleGrading (1 1 1) hex (8 13 12 11 23 28 27 26) (150 85 1) simpleGrading (1 1 1) ); edges ( ); patches ( patch inlet ( (0 15 24 9) ) patch outlet ( (3 18 29 14) (14 29 28 13) (13 28 27 12) ) symmetryPlane bottom ( (0 1 16 15) (1 2 17 16) (2 3 18 17) ) symmetryPlane top ( (9 10 25 24) (10 11 26 25) (11 12 27 26) ) patch obstacle ( (6 8 23 21) (6 21 20 5) (5 20 23 8) ) ); mergePatchPairs ( ); // ************************************************************************* // Code:
inconsistent point locations between block pair 1 and 3 probably due to inconsistent grading. Any ideas as to what I am doing wrong Thanks again very much for your help! |
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