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-   -   CAVITATION "no CONVERGENCE in non-cavitating flow" (https://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...

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...

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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