Converge issue on steady state pump

eleazar · August 17, 2012, 11:32

I have a mesh of a pump that has Boundary layers on the parts : blade, hub, shroud. it has periodic walls and inlet/outlet.

The BL mesh has elements with aspect ratio of 20000 and a number of jacobian with 0.42 the smaller.

I try to run this pump on CFX and the solver can not converge at the timestep of 1/ω, I am using SST as turbolence model.

If i apply timestep at 1e-9 the solver converge but the results are really bad.

Do you think that might be the mesh that creates the issue? or i have to check something else?

ghorrocks · August 18, 2012, 07:35

An aspect ratio of 20000 is pretty bad, even in a boundary layer mesh. I agree with you, I suspect you have inadequate mesh quality.

August 17, 2012, 11:32	Converge issue on steady state pump	#1
eleazar Member Elena Cortin Join Date: Mar 2009 Location: Paris Posts: 65 Rep Power: 17	I have a mesh of a pump that has Boundary layers on the parts : blade, hub, shroud. it has periodic walls and inlet/outlet. The BL mesh has elements with aspect ratio of 20000 and a number of jacobian with 0.42 the smaller. I try to run this pump on CFX and the solver can not converge at the timestep of 1/ω, I am using SST as turbolence model. If i apply timestep at 1e-9 the solver converge but the results are really bad. Do you think that might be the mesh that creates the issue? or i have to check something else?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Arithmetic mean of velocity (steady - state)	lentschi	CFX	3	January 11, 2011 06:18
Constant velocity of the material	Sas	CFX	15	July 13, 2010 08:56
steady state, laminar vof_model	Garima Chaudhary	FLUENT	0	May 24, 2007 03:11
About the difference between steady and unsteady problems	Lisa	Main CFD Forum	11	July 5, 2000 14:37
Steady state formulation of turbulence ??	Jitendra	Main CFD Forum	1	June 27, 2000 18:49

August 18, 2012, 07:35		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	An aspect ratio of 20000 is pretty bad, even in a boundary layer mesh. I agree with you, I suspect you have inadequate mesh quality.