DEFINE_UDS_UNSTEADY for Multiphase,apu,su meaning

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 December 7, 2006, 13:22 DEFINE_UDS_UNSTEADY for Multiphase,apu,su meaning #1 Anton Guest   Posts: n/a Hello Everybody! Do you have experience with DEFINE_UDS_UNSTEADY for _multiphase_ flows? In the FLUENT UDF manual, paragraph 2.7.4, we see the approximaton for the unsteady term for UDS: [unsteady term] = = -( (rho*phi)^(n) - (rho*phi)^(n-1) )/delta_t * delta_V = = apu + su, where apu = -rho * phi^(n) * delta_V / delta_t, su = -rho * phi^(n-1) * delta_V / delta_t. ^ here means the time step, not the power, of course. on the other hand, the natural idea to discretize the unsteady term is: apu = -rho^(n) * phi^(n) * delta_V / delta_t, su = -rho^(n-1) * phi^(n-1) * delta_V / delta_t. FLUENT's default is apu = -rho^(n-1) * phi^(n) * delta_V / delta_t, su = -rho^(n-1) * phi^(n-1) * delta_V / delta_t, though. The question is why does FLUENT take density values for calculating apu from the previous time step and not from the current time step? Thank you very much in advance!!

 December 11, 2006, 11:14 Re: DEFINE_UDS_UNSTEADY for Multiphase,apu,su mean #2 Anton Guest   Posts: n/a okay, i've found it out by myself. This is addressed in "FLUENT defects", ID 38858. It says it is an error in the FLUENT and it is fixed in version 6.3.1. cheers!

 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 dontknow Main CFD Forum 2 August 30, 2010 10:12 zhaoxinyu Fluent UDF and Scheme Programming 0 March 31, 2010 08:04 shyam FLUENT 1 July 29, 2008 06:25 Sangamesh CD-adapco 0 May 15, 2007 05:15 cfdbeginner CFX 0 November 27, 2003 10:02

All times are GMT -4. The time now is 23:25.

 Contact Us - CFD Online - Top