# turublence parameters.

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 February 26, 2007, 06:05 turublence parameters. #1 chandra Mohan Guest   Posts: n/a hi, i am simulating turbulent flow over a ellipse and rectangle. i want to know how to calculate the Turbulence Intensiyt(I) and what length scale to adapt. i am using fluent 6.2 software. also how to compute and meshing strategy for the wall Y+

 February 28, 2007, 10:34 Re: turublence parameters. #2 Pratik Mehta Guest   Posts: n/a turbulent intensity is given by standard deviation/mean velocity, where do u have to specify this number , i think it will either at the entrance or and exit ,depending on your domain , keep the value low at the exit to prevent the back flow , generally turbulent intensity is given very small, but yes this quite depending the case u r solving can u tell me whats your geometry ? Geting y+ is purely a trail n error method or a smart guess that comes from experience , or if u get a very simple geometry probably u must be in a position to get the estimation fo y+, Let me know have i answered u properly or not

 March 1, 2007, 00:16 Re: turublence parameters. #3 chandra Mohan Guest   Posts: n/a thnq for ur reply, my geometry is 2D, ellipse with max .length of 26m height of 11m. i want to specify the turbulence parameter at inlet velocity, also for y+ should be within 30. i am using fluent software to simulate external flow over an ellipse of major dia 2m and minor dia 1m. to calculate the drag and lift coefficient.

 March 1, 2007, 06:45 Re: turublence parameters. #4 Pratik Mehta Guest   Posts: n/a is the flow over the the major axis or minor axis, i mean the placement of the geometry with respect to the flow

 March 1, 2007, 06:53 Re: turublence parameters. #5 Pratik Mehta Guest   Posts: n/a knowledge of turbulence parameters at the entrance will come from the wind tunnel experiments , generally it is this way, but as far my experience is concerned , keepin the intensity about 0.001 should be ok , n for the outward it should be less 0.01% or something , or less enough to aviod the back flow at the pressure outlet i hope this helps u ,, other people reading this suggestion could u please put in suggestions over my comments

 March 1, 2007, 09:35 Re: turublence parameters. #6 chandra Mohan Guest   Posts: n/a major axis

 March 2, 2007, 03:57 Re: turublence parameters. #7 Ness Guest   Posts: n/a I've read the thread and I always put a turbulence int. of 1 for external flows at the inlet, and the same for the pressure outlet (in fact, this data are provided in the case of backflow, so the backflow is previous to the using of this data at the outlet). I recommend, in any case, to take some well-known cases and try to get the same results ( I mean, simple geomteries whose drag and lift are tabled) regards

 March 2, 2007, 07:24 Re: turublence parameters. #8 chandra Mohan Guest   Posts: n/a ok, thankyou, i will try that.

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