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tommy September 24, 2008 02:54

Natural convection cavities high rayleigh numbers
 
I'm doing some calculation on natural convection in cavities at high rayleigh numbers (Ra=10^10-10^16) and Pr = 0.71. I have serious convergence difficulties using a standard k-eps turbulence model. Does' anyone have any suggestions for me ??

Thanks you in advance

Rogerio Fernandes Brito September 25, 2008 07:25

Re: Natural convection cavities high rayleigh numb
 
change the scheme to upwind and try to see if it will converge or not.

Glenn Horrocks September 25, 2008 19:34

Re: Natural convection cavities high rayleigh numb
 
Hi,

The documentation has a discussion about obtaining convergence and you might get some ideas here: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

Note that it is common for flows at these Rayliegh numbers will converge steady state as they are almost always transient. Are you running in transient mode?

Glenn Horrocks

pratik mehta September 27, 2008 15:43

Re: Natural convection cavities high rayleigh numb
 
Hi, I have done very similar simulation using fluent 2 yrs back and I see that certainly one has to be very strategic to get convergence for natural convection simulations . I would suggest that you solve the case steady for few iterations but soon change to transient since as Glenn says and I agree most of such flow are transient in nature.

Best of lucky


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