solver control

katiyon · March 30, 2010, 11:55

i have a simple 2D model which is so similar to BUMP2D (examples in CFX help), a multiphase domain, (free surface)
and i want to make a model of cylinder under seabed, actually i have problem with solver control in cfx-pre,
i don't now how many iterations should be set, what kind a advection scheme, and my biggest problem is
Fluid timescale control.

ghorrocks · March 30, 2010, 18:18

Here's some tips:

Most free surface simulations are run transient. Convergence is very difficult steady state.

Use any high order advection scheme. Either hybrid with a large blend factor or high resolution.

Use adaptive timestepping, homing in on 3-5 coeff loops per timestep. If convergence is tricky then maybe increase to 4-8 coeff loops per timestep.

JDA · April 21, 2010, 15:29

As far as iterations needed, if you have the luxury of running it as a batch file and logging out, you can check it periodically and see how it is progressing. I have done this on Windows and Linux/Unix machines. It's a little different in each operating system (and your system admins may have certain restrictions on CPUs or runlevel), but it's not tricky in any case. Once you have an idea of how many iterations your simulation needs, you can take some multiple of that for the max number of iterations to be courteous to other users.

March 30, 2010, 11:55	solver control	#1
katiyon New Member kate Join Date: Jul 2009 Location: iran Posts: 29 Rep Power: 16	i have a simple 2D model which is so similar to BUMP2D (examples in CFX help), a multiphase domain, (free surface) and i want to make a model of cylinder under seabed, actually i have problem with solver control in cfx-pre, i don't now how many iterations should be set, what kind a advection scheme, and my biggest problem is Fluid timescale control.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Working directory via command line	Luiz	CFX	4	March 6, 2011 20:02
why the solver reject it? Anyone with experience?	bearcat	CFX	6	April 28, 2008 14:08
Solver Control via .pre file with Perl script	ahlo	CFX	1	March 7, 2008 12:33
Solver Control	Anantha	CFX	1	September 4, 2007 13:30
compressible two phase flow in CFX4.4	youngan	CFX	0	July 1, 2003 23:32

March 30, 2010, 18:18		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Here's some tips: Most free surface simulations are run transient. Convergence is very difficult steady state. Use any high order advection scheme. Either hybrid with a large blend factor or high resolution. Use adaptive timestepping, homing in on 3-5 coeff loops per timestep. If convergence is tricky then maybe increase to 4-8 coeff loops per timestep.

April 21, 2010, 15:29		#3
JDA New Member J. D. Aurand Join Date: Apr 2010 Posts: 13 Rep Power: 16	As far as iterations needed, if you have the luxury of running it as a batch file and logging out, you can check it periodically and see how it is progressing. I have done this on Windows and Linux/Unix machines. It's a little different in each operating system (and your system admins may have certain restrictions on CPUs or runlevel), but it's not tricky in any case. Once you have an idea of how many iterations your simulation needs, you can take some multiple of that for the max number of iterations to be courteous to other users.