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allan February 19, 2002 14:39

k-w turbulence model
 
Hi

I'm getting some conflicting information regarding the above with regards to wall boundary conditions. I've seen an analysis using a high Reynolds number version of the model where 3 < Y+ < 30, which I thought was wrong. Are the conventional U+ Y+ relationship valid with this model or does one need boundary conditions based on W+, and if so what are the range.

thanks in advance

allan

Thomas P. Abraham February 19, 2002 15:48

Re: k-w turbulence model
 
Hello Allan,

k-w model would a Low Reynolds number model. The governing equations are integrated down to the viscous sub-layer. The first node from the wall should below y+ = 1.

Thanks,

Thomas

allan February 20, 2002 04:15

Re: k-w turbulence model
 
Hi Thomas

The analysis that I saw the results of was definitely not a Low Reynolds analysis (I saw the mesh) If the Y+ values are what I said previously then they fall outside the the accepted range to be valid. What I really want to know is, are the U+ Y+ relationships valid with k-W or has David Wilcox suggested some new wall boundary relationship based on W.

Thanks

allan

Thomas P. Abraham February 20, 2002 11:44

Re: k-w turbulence model
 
Hello Allan,

Normally, U+ Vs Y+ relationship is nicely presented for a flat plate. It's hard to tell whether you are going see exactly the same behavior in all real world applications.

I would take U+ Vs Y+ relationship for a flat plate as a guide line independent of the kind of turbulence model I use.

As far as the boundary coundition for the turbulent frequency, omega is concerned, Wilcox has proposed the boundary condition in terms of the roughness parameter. This boundary condition is liked by many because it seems to be well behaved. Roughness paramter of 5 seems to be a good approximation for a smooth wall.

Bottom line is, when k-w model is used, the first node from the wall needs to be below y+ = 1.

Thanks,

Thomas

allan February 20, 2002 14:05

Re: k-w turbulence model
 
thanks

allan


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