# wall jet

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 June 2, 2010, 10:27 wall jet #1 New Member   chams Join Date: Apr 2010 Posts: 6 Rep Power: 7 Hi, please any information about wall jet ( turbulence model k-epsilon ) 10x

 June 2, 2010, 12:18 Hi #2 Member   Dynampally Pavitran Join Date: Mar 2010 Location: India Posts: 73 Rep Power: 7 1. Is it a plane wall jet( 2D- flow)? Then the flow is less complex than Three dimensional wall jet. The developing layer of plane wall jet is divided into an inner(boundary layer region) and an outer layer. Deciding upon which turbulence model to use depends on your goal. To resolve wall effects accurately use SST model. 2. Three dimensional wall jet Usually in 3D isothermal wall jets lateral spreading is larger than normal spreading due to stress induced secondary motions. Thus to accurately predict the flow mechanism of 3D-wall jets, one has to study the anisotropy of the Reynolds-normal stresses, which generate the stress induced axial voriticity. Therefore to predict correct behaviour of the 3D wall jets one has to apply anisotropic turbulence models such as the RSM (Reynolds stress model). The above information is just a gist about wall jets. Actually my Master thesis was on Wall Jets, therefore for further information you can contact me.

 June 2, 2010, 12:48 #3 New Member   chams Join Date: Apr 2010 Posts: 6 Rep Power: 7 Thank you very much PAVITRAN. Yes I need your help for more information about specially boundary conditions and numerical resolution in 2D - flow. & there's another question: why we use SST instead k-eps model? 10x

June 2, 2010, 22:18
Hi
#4
Member

Dynampally Pavitran
Join Date: Mar 2010
Location: India
Posts: 73
Rep Power: 7
Quote:
 Originally Posted by chams : why we use SST instead k-eps model? 10x
1. Basically K-epsilon model is a high reynolds number(local turbulent Re No in flow) model. Inorder to resovle the Viscous sublayer(where viscous diffusion dominates than turbulent diffusion) i.e. yplus < 5, K-epislon needs some damping functions.

2. SST model is used to resolve the viscous sublayer properly. Basically SST model predicts the separation and amount of separation properly.

3. But using SST model increases your mesh size, therefore if your interested in accurately predicting separation point, friction coefficient or heat transfer coefficient, then you should go with SST model.

For brief information about turbulence models please go through "WILCOX" or any other Turbulence modeling text books.

 June 3, 2010, 08:56 wall jet #5 New Member   chams Join Date: Apr 2010 Posts: 6 Rep Power: 7 Thank you for your explanation, I have the book "Turbulence Modeling for CFD" by David C. Wilcox http://uploading.com/files/75am4e74/TurbuleMod.rar/ But I need more your help, I'm searching for the book: "The Turbulent Wall Jet Measurements and Modeling" B E Launder, and W Rodi If you have this book please send me the link

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