# UDF for wall boundary condition

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

 October 21, 2009, 02:29 UDF for wall boundary condition #1 New Member   Suren L S Join Date: Oct 2009 Posts: 2 Rep Power: 0 Greetings. I am in need of some technical advice here. I am trying to simulate a cavity-filling flow. My geometry (2D) is a simple rectangle, and the two longest edges are the top and bottom wall. The other two edges are the 'velocity inlet' and 'pressure outlet' respectively, and the flow is from left to right. The cavity is initially filled with air and a viscous polymer enters via the velocity inlet at a fixed velocity. I am using a transient, segregated, laminar solver, with the VOF scheme to model the filling process. In addition I am also solving the energy equation and using a power law model to model the viscosity of the polymer. Right now, the solution converges, and the results are decent except for one particular problem. The layer closest to the wall remains as air and the polymer does not displace it at a reasonable rate - this results in a rather skewed flow front profile. I have read literature on this problem and some researchers have overcome this by using two sets of wall-slip conditions. No-slip for the viscous polymer and traction-free for the air. I am trying to do this as well, but am having quite a bit of trouble implementing this as a UDF. I would appreciate any help. Thanks. Suren

 October 23, 2009, 07:40 #2 Senior Member   Max Join Date: Mar 2009 Posts: 133 Rep Power: 8 Hello Suren, i think a no-slip BC is correct for both phases and should not be altered in any way. I would suggest to define surface tension and an appropriate wall contact angle to make your polymer the wetting phase. This should displace air from the adjacent wall cells effectively and in a physically sensible way. cheers

 October 28, 2009, 04:32 #3 New Member   Suren L S Join Date: Oct 2009 Posts: 2 Rep Power: 0 thanks a bunch for your suggestion. It should definitely be helpful to my work. Cheers

 Tags udf, uds, walls boundary conditions

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Nasir FLUENT 0 September 15, 2008 21:54 Jubs FLUENT 0 February 13, 2007 01:26 Sridhar FLUENT 3 July 13, 2001 19:18 Flav FLUENT 4 June 28, 2001 09:52 Jonas Larsson FLUENT 4 March 21, 2000 19:51

All times are GMT -4. The time now is 19:20.