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temperature going negative behind a bluff body

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Old   November 23, 2006, 07:56
Default temperature going negative behind a bluff body
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Sourabh
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I am trying solve a problem of high mach flow over a bluff body, when i switch on laminar code, temperature goes negative (suddenly) near wall behind the body, can anybody suggest me why it happens and any remedies or so?

Sourabh
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Old   November 28, 2006, 19:34
Default Re: temperature going negative behind a bluff body
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Carlos
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Sourabh,

I have a converged example with high mach number that I may send to you. Please send me your e-mail address.

About the negative temperatures: are you using Celsius or Kelvin? Negative temperatures are not always a wrong answer, especially in those occasions you have larges rarefactions.

You may also be experiencing convergence problems and you might use dense meshes to get the correct phenomenum.

If you send me your q1 file, I may try to have a look.

Regards,

Carlos.
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Old   November 29, 2006, 00:21
Default Re: temperature going negative behind a bluff body
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Sourabh
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I think u r right, i have a problem of large rarefaction, can it be avoided by use of dense meshes or are there any other treatments?

Sourabh
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Old   November 29, 2006, 06:13
Default Re: temperature going negative behind a bluff body
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Carlos
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Mesh is crucial but you may have to control MAX and MIN values of density, for instance.

Carlos.
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Old   November 29, 2006, 07:08
Default Re: temperature going negative behind a bluff body
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Sourabh
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i reduced CFL no. that helped the rarefaction i think , thank you.
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Old   November 7, 2007, 03:49
Default Re: temperature going negative behind a bluff body *NM*
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nahid
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Old   December 1, 2007, 19:50
Default Re: temperature going negative behind a bluff body
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patti
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You can set minimum allowed temperature(s) in MENU/Numerics/Limits on variables Patti
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