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Old   August 18, 2014, 23:00
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j3r
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Hi Wenjie,

Yes, it seems to work fine for me now. Was actually not that complicated once I figured out the syntax. Basically you can just copy the VHS sub-model, rename everything to VSS in the .C and .H file and in the .C file adjust the collision diameter and deflection angle according to the VSS model. Just check Bird or this paper for the details:
http://scitation.aip.org/content/aip....1063/1.858184

Of course you will also have to adjust some of the other files so that you can e.g. write alpha for each molecule into your dsmcProperties file and that dsmc knows that there is a new binary collision model (was in makeInflowModel.C or so I think). But which ones I would also have to look up, it's been a while since I worked on it. When you compile your code the error messages will tell you what is missing, e.g. if there are unknown variables that you have to define in another file or so.

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j3r
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Old   August 19, 2014, 04:29
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wenjie
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Quote:
Originally Posted by j3r View Post
Hi Wenjie,

Yes, it seems to work fine for me now. Was actually not that complicated once I figured out the syntax. Basically you can just copy the VHS sub-model, rename everything to VSS in the .C and .H file and in the .C file adjust the collision diameter and deflection angle according to the VSS model. Just check Bird or this paper for the details:
http://scitation.aip.org/content/aip....1063/1.858184

Of course you will also have to adjust some of the other files so that you can e.g. write alpha for each molecule into your dsmcProperties file and that dsmc knows that there is a new binary collision model (was in makeInflowModel.C or so I think). But which ones I would also have to look up, it's been a while since I worked on it. When you compile your code the error messages will tell you what is missing, e.g. if there are unknown variables that you have to define in another file or so.

Regards,
j3r
Thanks j3r, that's also what I thought. According to Bird's book, I should only change the deflection angle and the collision diameter to include alpha, the rest should be the same. Since in my case the diffusion is important, VSS is indeed necessary. I will also try to post my results here.

Cheers,
Wenjie
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Old   August 19, 2014, 07:00
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j3r
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Hi Wenjie,

Yes, that's right. Even though there are different equations to calculate the collision cross section. But they should all result in same value (more or less).

You will probably also be interested in this paper:
http://www.sciencedirect.com/science...09250913007252

Regards,
j3r
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