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-   -   CAVITATION "no CONVERGENCE in non-cavitating flow" (http://www.cfd-online.com/Forums/fluent/32554-cavitation-no-convergence-non-cavitating-flow.html)

ROOZBEH November 19, 2003 03:01

CAVITATION "no CONVERGENCE in non-cavitating flow"
 
Hi;

I want to model cavitation. I recently work with Fluent6.1.22. At the beginning of solution I work with a non-vavitating condition(high outlet pressure 50bar with my operating velocity 13m/s). If I turn on only the flow equations, the solutions converges; But at the same non-cavitating condition, if I add cavitation equation to the other equation,I do not have convergency(turbulence eq. converges but continuity do not converges) I did not have at least this problem with fluent6.0.12 !!!!!!! What settings are required for cavitating flow in this new version?

Thanks.

silver November 19, 2003 04:21

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
hi cav3d software can help you . I have no experience with Fluent . It may be able to help you . but resemlit of this actbitec help the convegency of other acctual cases may occur in nature or even in non-cavitating condition .

Dr. silverpole

.


mateus November 20, 2003 04:09

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
Hi!

On pressure outlet you have gauge pressure set to 50 bar? what's your operating pressure - 1 bar? As you know the sistem pressure is operating pressure + gauge pressure. It's good (in terms of convergence) to set operating pressure to a value about 1/2 of sistem pressure...I would set the operating pressure to 25 bar and gauge pressure on outlet to 25 bar...

Hope that this will help you...

Regards

MATEUS

mateus November 20, 2003 04:14

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
Hi again!

As mentioned in documentation (22.5.3) you can also change the amg solver setings... You find this at Solve-controls-multigrid...

regards

MATEUS

ROOZBEH November 22, 2003 03:19

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
Hi;

Thank you very much dear mateus! I will test with your suggestions. Oh, what did you mean about "sistem pressure"? Is it "absolut pressure" ?


ROOZBEH November 22, 2003 03:59

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
Hi; Can I ask you what pressure discretization schem should I use(I use PRESTO!) ? What pressure-velocity schem(I use SIMPLE)? I use under relaxation factor .2 for pressure,continuity,momentum,vaporization mass, vof and .5 for turbulence. When I run my case with a high pressure outlet, approximatly whole of domain have pressure with a value equal to max value! and a not good convergence of continuity equation.

ROOZBEH November 22, 2003 04:03

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
Hi again; Please excuse me. Where I should locate the reference point of operating pressure. I put it near leading edge of hydrofoil(CLE). Thanks

silver November 26, 2003 14:41

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
hi could you check the software I suggest ?

bye

Dr.silverpole

mateus November 28, 2003 05:00

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
Hi Roozbeh!

The presto scheme and simple algorithm look fine to me. The residuals look also in order. The thing I woul recomend is to move your reference point for operating pressure away from the hydrofoil - in the region where the flow conditions are constant...

Are you working on steady or unsteady simulation now?

Good luck

MATEUS

ROOZBEH December 1, 2003 03:51

Re: CAVITATION "no CONVERGENCE in non-cavitating f
 
Dear;

This software is not available for me. I will be happy to work with cav3d software for an experience.

Regards

Roozbeh Mousavi


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