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-   -   The question about Y+ (http://www.cfd-online.com/Forums/cfx/19276-question-about-y.html)

rambol November 4, 2002 04:24

The question about Y+
 
Hi,everyone.If I use low reynolds k-e turbulent model in gas-solid two-phase flow,Should I ensure the Y+ less than 1.0 for the gas and solid phase respectively?I have used fine mesh and the grid is 0.08mm at the bounday.but it diverged after some steps. who can give me some advice?thanks

Drona November 6, 2002 05:43

Re: The question about Y+
 
Hi Rambol,

I have been pondering over Y+ issues lately, so I thought I should write. I think you need to find out the boundary layer thickness(laminar sublayer) first and then decide on number of grid points within the layer. The CFX-TASCflow theory manual has a chapter on grid geneartion guidelines but not very clear. You may want to read that anyway. If your domain is a complex one, you will be hard pressed to ensure a desirable Y+ value everywhere in the domain.

Let's know if you have any joy with it.

Drona

rambol November 7, 2002 10:40

Re: The question about Y+
 
Thank you,Drona I use cfx-4.3 and calculate the dense gas-solid flow in a pipe.The minimum mesh near to the wall is 0.8mm .The result shows that the value of YPlus of gas is 0.8 and solid is 1.74e+05.I think it is very difficult to get the value of yplus less than 1 to solid phase through refining mesh.I use low Renolds k-e turbulent model. So should I must achieve the criterion for both phases that yplus should be less than 1 in low Renolds k-e turbulent model?


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