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Help: operating pressure for deflagration

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Old   October 18, 2010, 10:42
Default Help: operating pressure for deflagration
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Hello, everybody,

I am doing simulation of deflagration in a tunnel (flame propagation of premixed mixture). The mixture is ignited at one closed end of the tunnel. First, the Mach number <0.1, however,the flow velocity increase fast with time, and the Mach number also increase to a number larger then 0.1.

The reaction flow is treated as compressible flow.

The problem is how should I set the operating pressure in FLUENT6.3.26?
It's suggested in Fluent that when Mach number <0.1, operating pressure=mean flow pressure, while when Mach number >0.1, operating pressure=0 or mean flow pressure.

So what can I do.?
By the way, I use the density-based solver, so I can not use the floating operating pressure.

Thanks very much!

Last edited by fireman; October 18, 2010 at 11:54.
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Old   October 19, 2010, 10:07
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sreenivasa rao gubba
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Hi

check if you can overide by writing an udf in fluent? It is my guess only.

Sree
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Old   October 19, 2010, 10:14
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hi, Sree

Thank you. but I can not find the udf choice of operating pressure.
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Old   October 19, 2010, 11:01
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sreenivasa rao gubba
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hi Fireman

Can you clearly define, what do you mean by operating pressure. Do you want to set the entire domain at a pressrure equal to the experimental pressure? Do you want to devide your domain and setup two different pressure? Just eloborate a bit please.

Sree
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Old   October 19, 2010, 11:43
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hi Sree,

The operating pressure in fluent is used to reduce the roundoff error for low-Mach flow.

I want to setup the operating pressure equal to the mean flow pressure of the whole domain.
Or I need setup the operating pressure=mean flow pressure when Mach No.<0.1, operating pressure=0 when Mach No.>0.1

Now I don't know how to realize either of the two settings described above.

Thank you very much
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