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mach number and CFX 11.0 solver

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Old   December 24, 2008, 03:05
Default mach number and CFX 11.0 solver
  #1
turbinesv
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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!
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Old   December 24, 2008, 05:35
Default Re: mach number and CFX 11.0 solver
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Bart
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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

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Old   December 24, 2008, 10:19
Default Re: mach number and CFX 11.0 solver
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turbinesv
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Thanks for you advise, Bart.

Regards, Lan

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Old   December 29, 2008, 18:16
Default Re: mach number and CFX 11.0 solver
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John S.
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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
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Old   December 31, 2008, 12:03
Default Re: mach number and CFX 11.0 solver
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turbinesv
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John,your advice helps me a lot.

Thank you very much!
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Old   January 5, 2009, 06:43
Default Re: mach number and CFX 11.0 solver
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Glenn Horrocks
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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
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