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-   -   UDF sourse term for VOF equation (http://www.cfd-online.com/Forums/fluent/31281-udf-sourse-term-vof-equation.html)

ROOZBEH April 14, 2003 07:22

UDF sourse term for VOF equation
 
Hi,all users; I want to model supercavitation. But the cavitation molel of fluent can model only the inseption of cavitation and it is not enough for me. I mant to model the development of the cavitation. In the VOF equation of fluent, there is not a source term. therefore it can not model the mass transfer due a multiphase flow. I have written a UDF to add an appropriate mass source term to the mass equation of each phase,according to the suggestion of the fluent6 help. And I have compiled my UDF successfully. But durring the initialization I resived an "access violation" error. I have read fluent6 help and understood that I must refer each variable of each phase to a subthrad or subdomain. Please get me a guidline about it.

mateus April 14, 2003 12:18

Re: UDF sourse term for VOF equation
 
Which Fluent are you using? What geometry? I had some very good results using cavitation model in Fluent 6.1.18. Previous version was very unstable - it was impossible to get any converged results out of it. Regards MATEUS

roozbeh April 15, 2003 11:20

Re: UDF sourse term for VOF equation
 
Dear; I have Fluent 6.0.12. My geometry is a cylinder with a hemispherical head. If you read the help of Fluent6.0.12, you will see that this version of Fluent can not model the development of the cavity from its inception state.And can not model its collaps. If you search you found many papers about sheet cavitation, for example "Mr Inanc Senocak", "Mr Kunz et al." ets. Their source terms add to the VOF equation ,approximatly like together and differ from the source term used by fluent in its cavitation option. I want to use an interface tracking method. The mixture option in Fluent that includes cavitation option do not track the interface between the phases. In the cavitation option of Fluent the existance of cavity ,has no effect on the pressure contribution about the body. This causes it can not model the development of cavity and the collaps. Thank you.

mateus April 15, 2003 11:36

Re: UDF sourse term for VOF equation
 
Hi! Yes I agree. I have tried to implement the Barotropic cavitation model in Fluent but with no sucess. I think the model was developed by Reboud. They get very good results. regards MATEUS

ROOZBEH April 17, 2003 08:51

Re: UDF sourse term for VOF equation
 
Hi; Have Reboud used Fluent to model. Please get me some information about his works , or mail me his papers.

mateus April 22, 2003 06:56

Re: UDF sourse term for VOF equation
 
hi! I think Reboud used Numeca, but he had source code. I have only printed articles. I can only give you tese...

Coutier-Delgosha O., Fortes-Patella R., Rebound J.L.: Evaluation of turbulence model influence on the numerical simulations os unsteady cavitation; Proceedings of ASME FEDSM 01, 2001 ASME Fluids Engineering Division Summer Meeting, New Orleans, Louisiana, May 29-June 1, 2001

Lohrnberg H., Stoffel B., Fortes-Patella R., Rebound J.L.: Numerical and experimental investigations on the cavitation flow in cascade of hydrofoils; Procedings of the Fourth International Symposium on Cavitation, California Institute of Technology, Pasadena, California, USA, 20-23 June, 2001

I don't know anibody who came up with good results without source code. You can also look for PhD work of Habr - he used star-cd (also with source code): Gekopelte simulation hydraulischer gesamtsysteme unter einbeziehung von cfd.

and Sauer J.: Instation\"{a}r kavitierende Str\"{o}mungen - Ein neues Modell, basierend auf Front Capturing (VoF) und Blasendynamik - PhD Thesis; Universit\"{a}t Karlsruhe (TH), Karlsruhe, 2000 this one uses bubbledynamics model - similar to fluent

I can also send you some results that i got...

regards mateus


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