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turbulent expanding gases

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Old   March 30, 2009, 02:10
Default turbulent expanding gases
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Philip Kunz
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Hello, I am new to CFD and OpenFOAM. I am a software engineering student. I am taking a computer modeling and simulation class and for some reason I chose to do a CFD for the final project. I don't understand the math and I don't know what to do.

I have OpenFOAM running including Paraview. I have done some of the tutorials but I just don't know what to do. I have created the mesh that I would like to use.

Here's the code for it

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 .99619 0)
    (0.5 .99619 0)
    (0.5 1.00381 0)
    (0 1.00381 0)
    (0 .99619 .1)
    (0.5 .99619 .1)
    (0.5 1.00381 .1)
    (0 1.00381 .1)

    (0.5 0 0)
    (2.5 0 0)
    (2.5 2 0)
    (0.5 2 0)
    (0.5 0 .1)
    (2.5 0 .1)
    (2.5 2 .1)
    (0.5 2 .1)
);

blocks
(
    hex (0 1 2 3 4 5 6 7) (20 1 1) simpleGrading (1 1 1)
    hex (8 9 10 11 12 13 14 15) (20 20 1) simpleGrading (1 1 1)
);

edges
(
);

patches
(
    wall chamber
    (
    (0 4 7 3)
    )

    wall barrel
    (
    (3 7 6 2)
    (1 5 6 2)
    (0 1 5 4)
    )
    empty gunFrontAndBack
    (
    (0 3 2 1)
    (4 5 6 7)
    )
    empty airFrontAndBack
    (
    (8 9 10 11)
    (12 13 14 15)
    )

);
mergePatchPairs 
(
);

// ************************************************************************* //
I need gas to start expanding from the patch named "chamber". The idea for the model is a gun firing. I also need to appy this to a mesh that has a generic siliencer on hte end of the barrel. I don't know what kind of physics, math, etc to use. The only part I could ficure out was hot to make the mesh.

Please, any help is much appreciated.
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Old   April 1, 2009, 11:02
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Philip Kunz
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well.. since no one has responded. Can anyone tell me if this can even be done.

Would the blockDict i posted work? if not how do i change it? what rules must it conform to? all the systems I have seen use a square or curer environment. Do I need to do it like that in this case?

would rhoTurbFoam be used for this case?

I really need help I don't understand anything related to this other than programming. I have aken Physics enough to understand some electromagnetics, toque, inertia sound etc. But i don't know anything about gases beyong AP Chemistry, and even then that was 3 years ago.

This project is due Tuesday April 7th. I did not wait this long because of procrastination of because /i fogot. It was because I did not find out about openfoam until last week, and all other CFD programs I wanted to use previously were shot down.
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Old   April 17, 2009, 20:24
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Philip Kunz
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I have gotten a lot of work done on this, but I don't know how to continue.

I have been in contact with a student at Lehigh University who is getting his PhD in CFD focusing on incompressible flows. But he can't really give me anymore help ecause he doesn't know how openFoam works.

I don't know how to work in a moving mass such as a bullet, so I figured I would just work off of the assumption that once the bullet exits the barrel then it has no more effect on the gases. Thus I would set the initial pressure inside the barrel!

The Courant number starts out high and goes up exponentially and eventually it fails saying "Exceeded max number of iterations"

I don't have a tutorial that actually tells me what the different fields are for rhoTurbFoam. So I don't know how to change anything to actually produce results.

I've attached the blockMeshDict, setFieldsDict, u and p files. as for the omega, episilon, R, T and k files, I just copied the ones procided in the "tutorials/rhoTurbFoam/cavity/0" folder and copied stuff for each of the boundary types.

I have multiple different boundaries because it was easier to break it into parts like that when building the mesh. if that is the problem then let me know.

I have not changed any of the files provided in the rhoTurbFoam tutorials aside from the field dictionaries in the "0" folder
Attached Files
File Type: txt blockMeshDict.txt (11.8 KB, 3 views)
File Type: txt setFieldsDict.txt (1.1 KB, 4 views)
File Type: txt U.txt (1.9 KB, 2 views)
File Type: txt p.txt (1.6 KB, 3 views)
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