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

tut "Drop curve for cavitating Flow in the Pump"

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 22, 2012, 23:28
Default tut "Drop curve for cavitating Flow in the Pump"
  #1
Member
 
leo
Join Date: Jun 2012
Posts: 98
Rep Power: 5
sjtusyc is on a distinguished road
Today i have done the tutorial "Drop curve for cavitating Flow in the Pump".
Because the cavitation is taken into consideration, it is a multiphase problem.
In the domain settings, the homogeneous model is selected.
The documentation explain"The homogeneous model is selected because the interphase rate is large in the pump.This results in all fluids sharing a common flow field and turbulence."
I do not get it.
can someone explain to me ?
Thank you.
And whether the free surface model should be used?
Leo
sjtusyc is offline   Reply With Quote

Old   June 23, 2012, 06:29
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
One of the tutorial examples does a cavitating flow. Have a look at it for how to set up cavitation.

Homogeneous means that the different phases shaer a variable field, for instance velocity. If the velocity field is homogeneous then the two phases share the same velocity fields. The alternative is that each phase has its own velocity field and they interact with interphase slip on the differential velocity.
ghorrocks is offline   Reply With Quote

Old   June 23, 2012, 10:03
Default
  #3
Member
 
leo
Join Date: Jun 2012
Posts: 98
Rep Power: 5
sjtusyc is on a distinguished road
Glenn,thank you for your reply,
As my understanding, the homogeneous model is used under two conditions.
1)the phases are clearly stratified.
2)the drag dominated the flow with the absence of body force.eg.tiny particle in continuous phase.
The essence of the homogeneous model is the the transported quantities are shared,so,only one set of the PDES are needed ,that makes great simplification.
sjtusyc is offline   Reply With Quote

Old   June 23, 2012, 10:18
Default
  #4
Member
 
leo
Join Date: Jun 2012
Posts: 98
Rep Power: 5
sjtusyc is on a distinguished road
1)Glenn ,if we want to solve the control equations of the homogeneous model.We need additional control equation which controls the volume fraction.Right?How to set up that equation?
2)And the homogeneous model is always used with the free surface model.How to handle transition area?Is the homogeneous model is suitable for that area,if there is significant slip?
3)why need the free surface model as all the transported quantities can be given by the homogeneous model.what is free surface for?
sjtusyc is offline   Reply With Quote

Old   June 24, 2012, 07:18
Default
  #5
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
1) Several tutorial examples use multiphase modelling, some with free surface models. Have a look how they set it up.
2) No, homogeneous model can be used in either free surface or zero interphase slip flows, as your previous post says. What transition area are you referring to?
3) Do the tutorials and things will become clearer.
ghorrocks is offline   Reply With Quote

Old   June 24, 2012, 22:54
Default
  #6
Member
 
leo
Join Date: Jun 2012
Posts: 98
Rep Power: 5
sjtusyc is on a distinguished road
Thank you,i will turn to tutorial for help.
Last question, if two phases are stratified.eg:air is above the water,open channel flow.
Does there exist a interphase slip between the phases?
As the knowledge learned from the fluid dynamics,no slip right.right?So homogeneous +free surface is available.
Homogeneous model for shared variable field. free surface model for to capture good interface shape feature.
sjtusyc is offline   Reply With Quote

Old   June 24, 2012, 22:58
Default
  #7
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,662
Rep Power: 84
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
That is the usual approach. But have a look at the tutorial for the normal setup of a cavitating flow.
ghorrocks is offline   Reply With Quote

Old   June 24, 2012, 23:02
Default
  #8
Member
 
leo
Join Date: Jun 2012
Posts: 98
Rep Power: 5
sjtusyc is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
That is the usual approach. But have a look at the tutorial for the normal setup of a cavitating flow.
Thank you sincerely
sjtusyc is offline   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


Similar Threads
Thread Thread Starter Forum Replies Last Post
fluid flow fundas ram Main CFD Forum 5 June 17, 2000 21:31
Help: Poiseulle flow benchmariking Mohammad Kermani Main CFD Forum 1 November 12, 1999 17:15
Flow visualization vs. Calculated flow patterns Francisco Saldarriaga Main CFD Forum 1 August 2, 1999 23:18
Question on 3D potential flow Adrin Gharakhani Main CFD Forum 13 June 21, 1999 05:18
computation about flow around a yawed cone Tylor Xie Main CFD Forum 0 June 9, 1999 07:33


All times are GMT -4. The time now is 13:31.