# using UDF in Fluent for unsteady cavitation

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 October 22, 2008, 11:11 using UDF in Fluent for unsteady cavitation #1 Pejman Guest   Posts: n/a 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 âˆ' ρv)^10)/((ρl âˆ' 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

 October 22, 2008, 11:13 Re: using UDF in Fluent for unsteady cavitation #2 Pejman Guest   Posts: n/a By the way I have seen this solution in 2 papers but they have not described anything else!

 October 22, 2008, 11:22 Re: using UDF in Fluent for unsteady cavitation #3 mettler Guest   Posts: n/a 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.

 October 22, 2008, 16:16 Re: using UDF in Fluent for unsteady cavitation #4 Pejman Guest   Posts: n/a Thanks Mettler for your information. Do I have to identify the variables or the software recognize them already?

 October 22, 2008, 16:22 Re: using UDF in Fluent for unsteady cavitation #5 mettler Guest   Posts: n/a I would imagine you are going to have to identify them the same way Fluent does..

 October 23, 2008, 07:27 Re: using UDF in Fluent for unsteady cavitation #6 sandy Guest   Posts: n/a The following link might help you http://www.fluentusers.com/fluent/do.../udf/node3.htm

 November 6, 2008, 11:18 Re: using UDF in Fluent for unsteady cavitation #7 Pejman Guest   Posts: n/a Thanks Sandy, but I can not use it, since I can not register!

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