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1st order slip, Fluent, Urgent

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Old   November 3, 2013, 21:55
Default 1st order slip, Fluent, Urgent
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Karan Bansal
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Can anyone help me with how to implement first order slip condition to simulate rarefied gas flow (Kn = 0.3-0.7) in Ansys Fluent 13. If there is a tutorial available online? Could not find any.

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Old   November 4, 2013, 09:59
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Fluent has a boundary condition called "low-pressure boundary slip" that corresponds to a first order slip boundary condition for rarefied flows.
It is only available for laminar simulations.
Searching in the fluent manual for the name of this boundary condition will bring up all the information you need.

Nevertheless, a Knudsen number of 0.3...0.7 is way beyond the slip flow regime so the results will be poor.
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Old   November 4, 2013, 17:08
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Hello Flotus,

Thanks for your reply. The low pressure condition does not ask for any accomodation factor or any other parameter (like the velocity gradient at the all). Does Fluent define all those values by itself ?

Also from what i know, it is valid for flow over flat plates only (or maybe some airfoils with low curvature). I want simulations for a wavy wall (sinusoidal wave function). Do i need to write UDF for this ?

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Old   November 4, 2013, 18:28
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Accomodation factors and the other settings for the boundary condition become available in the materials tab as soon as the boundary condition is activated.
You are right, the derivation of this boundary condition implies a flat wall (curvature radius >> mean free path).
If you want the "correct" boundary condition for curved walls, a UDF is the only way.
However, even the slip boundary condition for curved walls implies a Knudsen number in the slip flow regime.
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