Poor convergence with high streamwise loss multipler

mullenc525 · September 21, 2011, 17:38

Hi,
I am doing flow distribution analysis where I am using a porous media to simulate many small channels within a heat exchanger. I want to force the flow to be parallel within the porous media, which necessitates a high streamwise coefficient multiplier. The difficulty I am having is when I make the multiplier much bigger than 10, the solution convergence becomes highly oscillatory and I can't get good convergence.
Any ideas?

ghorrocks · September 21, 2011, 20:20

I suspect the tips here will be relevant:

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

dvanb · September 23, 2011, 17:54

Apologies if I am not remembering this correctly, it's been a couple years since I did this kind of simulation, but:

you are saying you need a large stream-wise loss coefficient. I would think that in fact the directions _normal_ to the stream should have the very high loss coefficients to suppress crossflow. Your stream-wise coefficient should be whatever you need to simulate the expected pressure drop through the HEX for a given flow rate.

September 21, 2011, 17:38	Poor convergence with high streamwise loss multipler	#1
mullenc525 New Member Join Date: Dec 2010 Posts: 26 Rep Power: 15	Hi, I am doing flow distribution analysis where I am using a porous media to simulate many small channels within a heat exchanger. I want to force the flow to be parallel within the porous media, which necessitates a high streamwise coefficient multiplier. The difficulty I am having is when I make the multiplier much bigger than 10, the solution convergence becomes highly oscillatory and I can't get good convergence. Any ideas?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
how to understand high resolution scheme and high order scheme	iilw1314	Main CFD Forum	7	April 12, 2022 13:29
Temperature loss in compressible solvers in high speed flows	vkrastev	OpenFOAM Running, Solving & CFD	1	June 16, 2018 08:10
loss calculation in simulation of turbomachines	playmaster	Main CFD Forum	0	August 21, 2010 06:59
Directional loss model	Cenci	CFX	6	December 20, 2005 15:33
Multicomponent fluid	Andrea	CFX	2	October 11, 2004 06:12

September 21, 2011, 20:20		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,850 Rep Power: 144	I suspect the tips here will be relevant: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

September 23, 2011, 17:54		#3
dvanb New Member David VanBronkhorst Join Date: Sep 2011 Posts: 6 Rep Power: 15	Apologies if I am not remembering this correctly, it's been a couple years since I did this kind of simulation, but: you are saying you need a large stream-wise loss coefficient. I would think that in fact the directions _normal_ to the stream should have the very high loss coefficients to suppress crossflow. Your stream-wise coefficient should be whatever you need to simulate the expected pressure drop through the HEX for a given flow rate.