CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > Siemens > STAR-CCM+

Open Channel Flow Boundary Conditions

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 30, 2011, 16:50
Default Open Channel Flow Boundary Conditions
  #1
New Member
 
Join Date: Mar 2009
Posts: 14
Rep Power: 17
TWaung is on a distinguished road
Hi,

I am trying to model a simple open channel flow with an energy extraction device in the channel.

I am having difficulty specifying the inlet and outlet boundary conditions. Due to the presence of the energy extraction device (like an actuator disk modeled using a momentum source or porous region) , there is a head drop across the device.

I would like to set the water elevation at one boundary and then let the water elevation sort itself out at the other boundary.

I started with a velocity inlet and pressure outlet. I set the volume fraction ratios at the outlet using a field function. Then I set a constant inlet velocity ( I wasn't sure what to do with the VOF settings for the inlet). The resulting water elevations outlet were way off of the target...

Does anyone have suggestions on how to go about setting the inlet and outlet boundary conditions?

Here are some of the settings I am using

Physics Models:
- Implicit Unsteady
- K-e turbulence
- Eulerian Multiphase
- VOF
Phases
- Air, Water

Thanks for any suggestions!
TWaung is offline   Reply With Quote

Old   October 5, 2011, 20:56
Default
  #2
Senior Member
 
Join Date: Oct 2009
Location: Germany
Posts: 636
Rep Power: 22
abdul099 is on a distinguished road
Velocity inlet is fine. But what the hell do you mean, you are unsure about the VOF settings there? Don't you know your inlet conditions? Just specify a velocity profile and volume fractions and go ahead.
It should also be possible to try a pressure outlet as inlet condition when you're unsure about the inlet velocity. In this case, apply an appropriate pressure field (with hydrostatic pressure) and the volume fractions.

I'm not sure about a pressure outlet as outlet condition, as you have to specify conditions. The pressure boundary also allows an inflow when necessary, so it could occur and you have to specify values which often should be the result, no boundary condition. The water level at the outlet will be influenced from your outlet condition, especially from the pressure field you applied on the outlet. Therefore the result might be different due to your boundary condition, but that's no issue of the solver.
I think, I would try a get around this by choosing a flow split outlet (but I haven't tried, so better check it).
abdul099 is offline   Reply With Quote

Old   October 7, 2011, 01:37
Default
  #3
New Member
 
Join Date: Mar 2009
Posts: 14
Rep Power: 17
TWaung is on a distinguished road
Thanks for suggesting using the flow split outlet! That seems to be working well.
TWaung 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
Open Channel Flow ElanMorin FLUENT 4 February 25, 2015 17:26
Open channel flow motaba Main CFD Forum 4 March 26, 2011 04:22
Open Channel Flow Boundary Conditions. rahulrp FLUENT 0 December 1, 2010 08:32
VOF modelling open channel river flow Matthew Roberts FLUENT 6 July 31, 2009 13:52
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 16:55


All times are GMT -4. The time now is 03:03.