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Old   April 27, 2004, 11:52
Default method for best approximation?
  #1
Laszlo
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I would like to ask your help to select the best method for solving a flow problem.

There is an air channel 10mm x 2mm x 1mm and it is heated in a part of a channel. The air speed is between 0m/s and 50 m/s.

I would like to modell the effect of the heating to the velocity field and to the turbulence.

Do you think it will good approximate the real circumstances if I set the air material properties the following way: I set density as "ideal-gas" and set both viscosity and thermal conductivity as "kinetic-theory"?

What do you think which turbulence method gives the best approximation?

Thank you for your answer!
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Old   April 28, 2004, 01:48
Default Re: method for best approximation?
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FJ
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Hi,

In your case, the mesh needs to be very fine near all walls and the material property is set as a actual gas. "ideal-gas-law" is the good appoximation and the other properties should be a function of temperature or "kinetic theory" as your remarks.

I think "LES" is the best model.

Thanks

FJ
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Old   April 28, 2004, 10:22
Default Re: method for best approximation?
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Laszlo
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Thank you for your answer!

I will read books on turbulence soon... Maybe you know a simply answer so I put on the question.

If there is an real flow thing and I want to modell it with Fluent how do I know the best parameters for turbulence specification (at inlet velocity parametrisation)? And if I select intensity and length scale, which values gives the best approximations to the real circumstances? Could you give me some suggestions please?

Thank you in advance!
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Old   April 28, 2004, 18:35
Default Re: method for best approximation?
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co2
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Laszlo:

answer to your question is in the online help for fluent 6.1

please read chapter 6. Boundary Conditions

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Old   April 29, 2004, 04:17
Default Re: method for best approximation?
  #5
Laszlo
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Your answer was useful! Thanks! In velocity inlet part I read I shouldn't use velocity inlet with compressible flows.

At chapter 6.2.2. there is a calculation method for Turbulence Length Scale in duct flow. It was helpful too.

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