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

What is proper boundary condition to model Pump inlet in a multiphase simulation?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 24, 2017, 12:56
Default What is proper boundary condition to model Pump inlet in a multiphase simulation?
  #1
Senior Member
 
sluzzer
Join Date: Jul 2014
Posts: 129
Rep Power: 5
shivasluzz is on a distinguished road
A vented tank is connected to a scavenge pump (gear pump). If there is no liquid or insufficient liquid, then the pump will suck the air also.
I don't want to model the pump. Instead I like to give an appropriate boundary condition at the end of pipe which is connected to the pump.
What boundary condition I should apply here? Mass flow rate or Pressure or any other method?
Thanks
shivasluzz is offline   Reply With Quote

Old   June 25, 2017, 19:05
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,881
Rep Power: 107
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
Sounds like a constant volume flow rate would be a suitable boundary condition. You can impose this using a defined velocity at the boundary.
ghorrocks is offline   Reply With Quote

Old   June 26, 2017, 00:16
Default
  #3
Senior Member
 
sluzzer
Join Date: Jul 2014
Posts: 129
Rep Power: 5
shivasluzz is on a distinguished road
During testing of the pumps, I observed if we change the diameter of inlet (auction) pipe, the outlet flow rate is varying.

So I think constant flow rate boundary condition is not the right choice to simulate the actual condition.

My understanding is that the flow in the suction pipe is due to the pressure difference between the pressure at tank and the pressure at the inlet of pump. However, the flow rate in the outlet of pipe is constant and it does not varies with change in pipe diameter.

However I don't know how it behaves when it turns into multiphase.

I have the test data of inlet pressure when the pump is tested only in single phase (oil). Can I use the same inlet pressure value for the multiphase simulation?




Sent from my iPhone using CFD Online Forum mobile app
shivasluzz is offline   Reply With Quote

Old   June 26, 2017, 19:15
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,881
Rep Power: 107
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
The basic rule of boundary conditions is: You have to know the flow conditions at a boundary to define a boundary condition there. If you do not know the flow conditions at a boundary then you can't put a boundary there - so you need to move the boundary somewhere you do know the flow conditions, or you need to get more data until you know the boundary condition.
ghorrocks 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
Multiphase flow - incorrect velocity on inlet Mike_Tom CFX 6 September 29, 2016 01:27
Suitable inlet boundary condition for a compressible flow simulation siw FLUENT 12 September 12, 2016 08:08
Radiation in semi-transparent media with surface-to-surface model? mpeppels CFX 10 June 16, 2015 15:48
Low Mixing time Problem Mavier CFX 5 April 29, 2013 00:00
RPM in Wind Turbine Pankaj CFX 9 November 23, 2009 05:05


All times are GMT -4. The time now is 16:08.