# CAV and VOF

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 October 3, 2007, 23:11 CAV and VOF #1 Eli Guest   Posts: n/a Hi guys, I am calculating the cavitation of LPG Pump, and my question is: What is difference between CAV and VOF? and other question, what exactly happen when free surface option turn on. Must free surface turned on for calculating cavitation in pump operation. thank you a lot an advance for your response, regards

 October 8, 2007, 08:50 Re: CAV and VOF #2 Anton Lyaskin Guest   Posts: n/a CAV represents vapour of liquid, VOF represents liquid. VOF appears only if you run cavitation simulation with free surface option. For pump operation simulation it's usualy not necessary to turn it on (this will depend upon particlar case, actually) - it makes sence only if you have big cavitation caverns, fully filled with vapour, while in the pump you'd rather have small "subscale" (i.e. smaller than your cell size) bubbles. You can make a simulation without free surface, and then check - if you have big areas with high values of CAV, then it makes sence to turn on free surface option, because these areas will results in big cavitation caverns. With free surface option they will be modelled in a "usual free-surface way", with interface tracking and etc.

 October 11, 2007, 03:56 Re: CAV and VOF #3 Eli Guest   Posts: n/a thanks a lot Mr. Anton I really appreciate your help, one more question guys: In my model the Reynolds number is equal to 23150, so I used K-Epsilon/High-Reynolds turbulence model, for cavitation model there are three models Barotropic, BTF and Rayleigh. First I calculated cavitation with Barotropic, Rayleigh models ,and results are almost same in these two models. But result is totally different with BTF model from other cavitation models. which cavitation model is usually used in this kind of PUMP calculation. Any suggestions are welcome! Regards

 October 11, 2007, 06:22 Re: CAV and VOF #4 Anton Lyaskin Guest   Posts: n/a BTF is the most appropriate for the case, when big cavitation caverns tend to appear. But there is no general rule which model should be applied for which case. It will depend upon pump design, flow rate and many other factors. If you have some experimental results, it's better to compare with them. Otherwise you should look for papers on cavitation modeling for pumps and choose one with the design closest to yours.

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