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using UDF in Fluent for unsteady cavitation

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Old   October 22, 2008, 11:11
Default using UDF in Fluent for unsteady cavitation
  #1
Pejman
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Hi,

I am working on 3D cavitation modeling of a hydrofil using Fluent 6.2.16 . The problem I have countered is that the k-epsilon RNG model itself can not simulate the unsteady behavior of cavitation. It just simulate the inception of the cavities. And then the flow becomes steady withoud any Re-entrant jet or cloud cavitation separation.

To solve this problem, I have to define a UDF that correct this problem by this way:

μt=f(&rho*Cμ*k^2/ε

f(&rho=ρv+((ρm ' ρv)^10)/((ρl ' ρv)^9)

Can anybody help me to define a UDF for it? Actually I don't know anything about UDF's in Fluent. Just give me a hint or tell me the works I have to do.

Thanks

Pejman
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Old   October 22, 2008, 11:13
Default Re: using UDF in Fluent for unsteady cavitation
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Pejman
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By the way I have seen this solution in 2 papers but they have not described anything else!
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Old   October 22, 2008, 11:22
Default Re: using UDF in Fluent for unsteady cavitation
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mettler
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from what I can remember, you have to convert that into a C+(?) code..compile it etc. Then, within Fluent you call it up. You have to make sure that you pass the correct variables thru.
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Old   October 22, 2008, 16:16
Default Re: using UDF in Fluent for unsteady cavitation
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Pejman
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Thanks Mettler for your information. Do I have to identify the variables or the software recognize them already?
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Old   October 22, 2008, 16:22
Default Re: using UDF in Fluent for unsteady cavitation
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mettler
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I would imagine you are going to have to identify them the same way Fluent does..
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Old   October 23, 2008, 07:27
Default Re: using UDF in Fluent for unsteady cavitation
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sandy
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The following link might help you http://www.fluentusers.com/fluent/do.../udf/node3.htm
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Old   November 6, 2008, 11:18
Default Re: using UDF in Fluent for unsteady cavitation
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Pejman
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Thanks Sandy, but I can not use it, since I can not register!
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