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

Weak rotational flow - Convergence Problems

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 6, 2009, 03:48
Default Weak rotational flow - Convergence Problems
  #1
New Member
 
Dag Stromsvag
Join Date: Apr 2009
Posts: 6
Rep Power: 17
Daggemann is on a distinguished road
Hi,

I am simulating seawater flow in a subsea particle filtration unit, with weak to moderate rotating flow induced by stationary curved fins.

I get convergence using all k-epsilon models using SIMPLE pressure.velocity coupling, but when switching to k-omega (standard and SST) the solution only converge for 1st Order Upwind. When switching to higher order schemes the residual oscilliates around a specific point quite far from the convergence criteria of 0.001. It is mainly the continuity residual that struggles.

I have tried under-relaxation and PISO, but they dont do the job.

As inlet condition I have velocity inlet, and the outlet is an outflow. Most of the flow is laminar, but a certain region is turbulent so I figured I had to use turbulent modelling.

Is there any basic steps I can apply in order to figure out the problem, and is it possible that the k-omega turbulence modelling law just doesn't apply in this case?

ty
Daggemann is offline   Reply With Quote

Old   May 8, 2009, 10:45
Default
  #2
Member
 
Ralf Schmidt
Join Date: Mar 2009
Location: Austria
Posts: 67
Rep Power: 17
Ralf Schmidt is on a distinguished road
Hi!

I have no experience with water, but it could be, that there are problems with your grid - see also: http://www.cfd-online.com/Forums/flu...cillation.html

If just some region is turbulent, you might use a "laminar zone" in this regions to suppresses all turbulence (in the fluid BC).

Another option would be, to change the gradient option (-> define -> models -> solver) . I have no idea, what is really behind this settings, but they helped me sometimes...

Hope, that helps a little.
Ralf
__________________
CFD - nothing but Colourful Fluid Dynamics
Ralf Schmidt is offline   Reply With Quote

Reply


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
Flow meter Design CD adapco Group Marketing Siemens 3 June 21, 2011 09:33
convergence problems using SBF=1 Fonzie CFX 1 March 23, 2007 09:46
Convergence problems with SSG turbulence model Ram CFX 1 June 19, 2006 11:08
Convergence problems Emilien FLUENT 3 May 3, 2002 09:43
convergence problems david aquilina Siemens 4 October 27, 2000 10:18


All times are GMT -4. The time now is 06:14.