two turbulence model in fluent

duaiduaihu · August 26, 2009, 09:02

in fluent we can choose standard ke model and wall function to solve the problem. we also know that low Re ke model is more accurate than the wall function!
my question is can we select different turbulent models in the fluent for different sub_domain?
thanks!

jalarron · August 26, 2009, 19:39

If you are asking a method of applying k-e into one zone and a Low Reynolds ke into another zone, it is possible to do it using UDF's that patch the k-e and momentum equations for the Low rey formulation.
I've seen some papers that add some model functions that change the value of the coefficients and add extra source terms as a function of y_star and Re=k^2/nu*e.
But in this case the problem is to override the wall functions that are in-built in Fluent, use DEFINE_WALL_FUNCTION macro.

The easiest way is using k-w-sst formulation that takes care of the near wall region better than k-e, doesn't use wall functions. The only precaution is to have a fine mesh near the wall. Look at the Fluent Doc, what Y+ or Y* is recommended.

Hope it gives you a better idea on what to do.

Regards,
Javier

August 26, 2009, 09:02	two turbulence model in fluent	#1
duaiduaihu New Member Eric Join Date: Apr 2009 Posts: 23 Rep Power: 17	in fluent we can choose standard ke model and wall function to solve the problem. we also know that low Re ke model is more accurate than the wall function! my question is can we select different turbulent models in the fluent for different sub_domain? thanks!

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August 26, 2009, 19:39		#2
jalarron New Member Javier Larrondo Join Date: Jun 2009 Posts: 17 Blog Entries: 1 Rep Power: 17	If you are asking a method of applying k-e into one zone and a Low Reynolds ke into another zone, it is possible to do it using UDF's that patch the k-e and momentum equations for the Low rey formulation. I've seen some papers that add some model functions that change the value of the coefficients and add extra source terms as a function of y_star and Re=k^2/nue. But in this case the problem is to override the wall functions that are in-built in Fluent, use DEFINE_WALL_FUNCTION macro. The easiest way is using k-w-sst formulation that takes care of the near wall region better than k-e, doesn't use wall functions. The only precaution is to have a fine mesh near the wall. Look at the Fluent Doc, what Y+ or Y is recommended. Hope it gives you a better idea on what to do. Regards, Javier