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-   -   temperature going negative behind a bluff body (https://www.cfd-online.com/Forums/phoenics/52120-temperature-going-negative-behind-bluff-body.html)

 Sourabh November 23, 2006 07:56

temperature going negative behind a bluff body

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

 Carlos November 28, 2006 19:34

Re: temperature going negative behind a bluff body

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.

 Sourabh November 29, 2006 00:21

Re: temperature going negative behind a bluff body

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

 Carlos November 29, 2006 06:13

Re: temperature going negative behind a bluff body

Mesh is crucial but you may have to control MAX and MIN values of density, for instance.

Carlos.

 Sourabh November 29, 2006 07:08

Re: temperature going negative behind a bluff body

i reduced CFL no. that helped the rarefaction i think , thank you.

 nahid November 7, 2007 03:49

Re: temperature going negative behind a bluff body *NM*

 patti December 1, 2007 19:50

Re: temperature going negative behind a bluff body

You can set minimum allowed temperature(s) in MENU/Numerics/Limits on variables Patti

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