CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   CFX (http://www.cfd-online.com/Forums/cfx/)
-   -   mach number and CFX 11.0 solver (http://www.cfd-online.com/Forums/cfx/26840-mach-number-cfx-11-0-solver.html)

turbinesv December 24, 2008 02:05

mach number and CFX 11.0 solver
 
Hi everyone!

I am going to simulate supersonic flow with the mach number of about 2.0 using CFX 11.0. But I am not familiar with the supersonic flow. Can anyone tell me at what range of mach number the CFX solver can give reliable results?

Thanks in advance!

Bart December 24, 2008 04:35

Re: mach number and CFX 11.0 solver
 
Mach 2 should be fine. Some tips: Set expert parameter max continuity loops = 2 Start run with local timestep. Once converged switch to physical timestep (if problem is steady) Use SST turbulence model


turbinesv December 24, 2008 09:19

Re: mach number and CFX 11.0 solver
 
Thanks for you advise, Bart.

Regards, Lan


John S. December 29, 2008 17:16

Re: mach number and CFX 11.0 solver
 
Sometimes I get funky residuals from the energy equation using max continuity loops = 2. You might try starting the simulation with less aggressive BCs for subsonic flow to give CFX a chance to resolve the flowfield. Once you have a converged subsonic result you can step up gradually to your supersonic boundary conditions. This will help aid convergence.

John

turbinesv December 31, 2008 11:03

Re: mach number and CFX 11.0 solver
 
John,your advice helps me a lot.

Thank you very much!

Glenn Horrocks January 5, 2009 05:43

Re: mach number and CFX 11.0 solver
 
Hi,

In my experience all of these suggestions are problem dependent - I have never found the max cont loops to help but I have found starting with local timestepping and switching to physical timestepping after things settle down a bit works well. Obviously you will have to try them on your simulation and see what works.

Glenn Horrocks


All times are GMT -4. The time now is 09:56.