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-   -   laminar transision turbulent zones (http://www.cfd-online.com/Forums/fluent/36826-laminar-transision-turbulent-zones.html)

Rama krishna June 2, 2005 06:55

laminar transision turbulent zones
 
hi i am rama krishna student of iit madras.

can any one help me in modelling laminar transition and turbulent regions in natural convection over a vertical flat plate. i just want to model all the three regions and i got stucked what are the boundery conditions that i have to give to model all the three regions.

regards

thanking you.

jorge sancho June 2, 2005 13:31

Re: laminar transision turbulent zones
 
Have you tryed defining different fluid volumes, and changing the viscous models in each one?. Is the only way i have found to force the laminar-turbulent trasition... Regards

us June 2, 2005 21:48

Re: laminar transision turbulent zones
 
Hi jorge,

Would you please explain in more detail how to do so? Thanks for you time. -US

rama krishna June 2, 2005 23:55

Re: laminar transision turbulent zones
 
thank you for your valuable suggestion and till now i have not tried in that way now i will do that. but what the code will do i mean can't it predict the different zones?

regards

rama krishna

Evan Rosenbaum June 3, 2005 13:56

Re: laminar transision turbulent zones
 
FLUENT cannot predict the transition from laminar to turbulent. Some of the turbulence models will do low Re flows, but not laminar. You either need to define separate fluid regions with different regimes (i.e., laminar in one and turbulent in another) or write a UDF to check presence of turbulence and disable turbulence production if the flow is actually laminar.

us June 3, 2005 14:18

Re: laminar transision turbulent zones
 
Hello Evan,

A question here. How do we define different viscous model in different regions for a single fluent case. For example, for a flow through domain, you chose one of the viscous models ie either laminar or turbulent(k-e etc.). Can we really specify different flow regimes(turbulent and laminar) together in a one single fluent running case? Please explain.

Thanks a lot for your time. -US

Evan Rosenbaum June 6, 2005 14:52

Re: laminar transision turbulent zones
 
I you want to have turbulence in some zones and laminar flow in others, you would enable the turbulence model you want. Then, turbulence can be suppressed on a zone-by-zone basis in the boundary conditions panel, where there is a "Laminar Region" option toggle.

us June 6, 2005 16:31

Re: laminar transision turbulent zones
 
thanks, Evan.


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