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

VOF and BED ROUGHNESS

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 6, 2004, 10:40
Default VOF and BED ROUGHNESS
  #1
Nial Horton
Guest
 
Posts: n/a
Dear friends,

i am a research assistant using gambit and fluent to study shallow flow in the river ehen in the lake district.

i have been using a fixed lid approach with the k-epsilon model and have found it very difficult to accurately describe the bed roughness. it says in the user manual for fluent that "it is not physically meaningful to have a mesh size such that the wall-adjacent cell is smaller than the roughness height. For best results, make sure that the distance from the wall to the centroid of the wall-adjacent cell is greater than the roughness height".

My cell size was created from a edge mesh size of 0.1 so i was hoping that you may be able to tel me a range of roughness sizes that would be suitable to investigate.

Secondly, due to the depths being studied it is becoming less and less practical to use the fixed lid method and i have studied the use of the VOF model. i split the inlet and outlet into two by specifying a normal distance from the bed and creating an isovalue region and now have patched the water and air into the respective volumes but i cannot get the simulation to converge between 10 and 20 iterations even when using a very small step size.

anything u can suggest to remedy this problem would be amazingly helpful

thank you very much for your time

Nial
  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
urgent... multiphase cfd model of packed bed reactor.( VOF MODEL using) balu@gold6 FLUENT 4 July 26, 2012 10:37
a problem of incompressible two phases(water and gas) with VOF Method zhangweisnoopy Main CFD Forum 9 August 12, 2011 08:25
CFD for Rotating Bed MP Main CFD Forum 3 January 4, 2003 11:30
VOF, liquid Velocity CFD MAN FLUENT 2 November 24, 2002 01:19


All times are GMT -4. The time now is 06:32.