CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CD-adapco

CAV and VOF

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   October 3, 2007, 23:11
Default 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
  Reply With Quote

Old   October 8, 2007, 08:50
Default 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.
  Reply With Quote

Old   October 11, 2007, 03:56
Default 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
  Reply With Quote

Old   October 11, 2007, 06:22
Default 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.
  Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 17:15.