# Buoyancy generated Turbulence flow

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 July 13, 2006, 10:49 Buoyancy generated Turbulence flow #1 Nitesh Guest   Posts: n/a Hi all I am simulating a buoyancy driven flow to compute heat transfer and temperature profile inside a spherical vessel. My simulations involved high Rayleigh Number of order of 10^7 or higher as I have to find the above parameter at high pressure range. So I have included K-epsilon turbulence model along with Boussinesq approximations. My problem is, I am still unable to find the parameter c3 Epsilon in the list of turbulence specifying parameter, as mentioned in fluent manual, that affects the allignment of gravity and boundary shear flow. Kindly help me in finding if 1. If there is any other approach to specify this parameter C3 epsilon than specifying in turbulence parameter panel. 2. Kindly explain the effect of this parameter on the sensitivity of results 3. Is this is due to some error that I might have made in specifying other parameters. Thanks in advance Regards Nitesh.

 July 13, 2006, 18:58 Re: Buoyancy generated Turbulence flow #2 Khyati Guest   Posts: n/a Hey, I am trying to solve Flow over a heated cylinder in a contra Flow(vertically downward direction) using Fluent, at Re = 130 and Richardson number between 0.0. and 1.0. This arrangement also gives a buoyancy driven flow. I had tried using the Boussineq approximation but didnt work. So I had to use density as a function temperature ands seems to give reasonable results for lower temperatures. But there are complications with the higher temperatures. What is the Re that you are using? Do you think that at Re=130 and Richardson number =1.0 for a flow over a heated cylinder the flow becomes turbulent? I also have problems in calculating the Cd. In references do you take the area= radius x depth or dia x depth. I tried taking dia X depth and seeems to give nearly half of what it should. Is there any other way that I could calculate the Cd. I would really appreciate any help from you. Thanks Khyati

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