CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Cavitation Modelling Options

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   August 10, 2012, 22:10
Default Cavitation Modelling Options
  #1
Member
 
Join Date: Jan 2012
Location: Edmonton, CA
Posts: 87
Rep Power: 14
Torque_Converter is on a distinguished road
Send a message via AIM to Torque_Converter
I'm working on properly modelling cavitation and I know I have some options, but some very incomplete data. I was hoping I could get some of your guys expert guidance on which way to go.

I would like to model the oil vapor as an ideal gas, but I do not know the molar mass, in fact I have NO clue. With the other properties I have some idea. I know density, mean particle size, dynamic viscosity, and saturation pressure at 90 C, the temperature of isothermal operation.

I know instead of ideal gas I could program in properties vs. pressure. If I somehow make an educated guess at this, would it be better than attempting to use ideal gas, or not? If so, how would I write CEL code for rho(P) for example? I haven't seen much in the literature.

Also, if anyone has any insights on the vapor properties of an oil with density at 90 C of about 800 kg/m^3 it would be of great help.

Thanks all

P.S. any additional tips on cavitation modelling you can add that I may not have asked about would also be greatly appreciated to build the best model I can.
Torque_Converter is offline   Reply With Quote

Old   August 12, 2012, 09:09
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I would not bother modelling the vapour as an ideal gas. Its properties are so far away from an ideal gas as to be not worht the effort.

I assume you are currently assuming a fixed density vapour. Before doing anything on variabel density vapours I would do a sensitivity analysis to determine if it makes any difference. Try doubling and halving the vapour density and see if it makes any difference to the results. If it makes no difference then I think you will find variable density is insignificant and so not worth implementing.
ghorrocks is offline   Reply With Quote

Old   August 12, 2012, 13:08
Default
  #3
Member
 
Join Date: Jan 2012
Location: Edmonton, CA
Posts: 87
Rep Power: 14
Torque_Converter is on a distinguished road
Send a message via AIM to Torque_Converter
That sounds like a good strategy to go forward on. I have a feeling that changing the constant density won't do much.

What seems to be lacking is the drop off in torque production at higher RPMs.

The reason I was grasping for some perfect cavitation/vapor modelling is because I have this device that I just can't get. I thought I had nailed every other factor (geometry, boundary conditions, liquid properties, speed/conditions of test). I guess cavitation, while present in the model, is unlikely to resolve my problems by taking a guess at what might be slightly more accurate, or very likely, no more accurate.
Torque_Converter is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Cavitation modelling madcfd STAR-CCM+ 1 June 1, 2012 23:12
Cavitation modelling in inducer! Rafael FLUENT 1 July 25, 2011 03:25
Cavitation modelling in inducer! Rafael FLUENT 0 June 26, 2007 13:09
Cavitation modelling !!! ROOZBEH Fidelity CFD 5 May 21, 2004 02:39
CAVITATION (STEADY MODELLING) ROOZBEH FLUENT 2 January 21, 2004 03:47


All times are GMT -4. The time now is 11:57.