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-   -   using UDF in Fluent for unsteady cavitation (http://www.cfd-online.com/Forums/main/15911-using-udf-fluent-unsteady-cavitation.html)

Pejman October 22, 2008 11:11

using UDF in Fluent for unsteady cavitation
 
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(ρ)*Cμ*k^2/ε

f(ρ)=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

Pejman October 22, 2008 11:13

Re: using UDF in Fluent for unsteady cavitation
 
By the way I have seen this solution in 2 papers but they have not described anything else!

mettler October 22, 2008 11:22

Re: using UDF in Fluent for unsteady cavitation
 
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.

Pejman October 22, 2008 16:16

Re: using UDF in Fluent for unsteady cavitation
 
Thanks Mettler for your information. Do I have to identify the variables or the software recognize them already?

mettler October 22, 2008 16:22

Re: using UDF in Fluent for unsteady cavitation
 
I would imagine you are going to have to identify them the same way Fluent does..

sandy October 23, 2008 07:27

Re: using UDF in Fluent for unsteady cavitation
 
The following link might help you http://www.fluentusers.com/fluent/do.../udf/node3.htm

Pejman November 6, 2008 11:18

Re: using UDF in Fluent for unsteady cavitation
 
Thanks Sandy, but I can not use it, since I can not register!


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