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October 27, 2015, 06:29 
kw SST freestream values for w

#1 
New Member
Syed Aaquib Hazari
Join Date: Apr 2015
Location: Delft
Posts: 16
Rep Power: 3 
Dear all,
I want to know the freestream values of the blending function for 'w' in kw SST. Additional details: I am trying to simulate the kw SST for a two phase channel flow on MATLAB and I am having problems obtaining the accurate blending function values. The blending function is as follows: arg1=min(max(sqrt(k)/(0.09*w*y),500*nu/(y^2*w),4*sigma_w_2*k/(CD*y^2)) F_1=tanh(arg1^4) Where 'y' is the nearest distance to any surface, sigma_w_2 is a closure coefficient CD is the cross diffusion modification The values of F_1 should be 1 for near wall (implying kw is switched on) & 0 for freestream values (implying ke is switched on. However, I am obtaining incorrect values for the function. After reading through the SST model Menter mentions about freestream values for 'w'. I do not know what these values are. If anyone does please let me know. Thanks! 

March 16, 2016, 02:07 

#2 
Senior Member
Ashwani
Join Date: Sep 2013
Location: Hyderabad
Posts: 100
Rep Power: 5 
Hi,
Were you able to solve this issue ? wr 

March 16, 2016, 06:16 

#3 
New Member
Syed Aaquib Hazari
Join Date: Apr 2015
Location: Delft
Posts: 16
Rep Power: 3 
Hi Ashwani,
I did manage to proceed ahead. Can you be more specific? 

March 17, 2016, 01:41 

#4 
Senior Member
Ashwani
Join Date: Sep 2013
Location: Hyderabad
Posts: 100
Rep Power: 5 
Hi,
How is the values of blending function calculated at the boundary faces. The value of sigma_k , sigma_omega in diffusion term of komega and turbulent viscosity at the boundary face requires the value of blending function. How to handle them? Thanks and regard Ashwani 

March 18, 2016, 05:29 

#5 
New Member
Syed Aaquib Hazari
Join Date: Apr 2015
Location: Delft
Posts: 16
Rep Power: 3 
Hi,
So, the values of omega at the boundary faces is, as given by Menter At the wall boundary omega=10*(6*nu/(beta_1(del_y)^2) k=0 Where, nu is the kinematic viscosity of the fluid, beta_1 is a closure coefficient and del_y is the distance between the first two cells. The values of sigma_k & sigma_omega are not calculated at the boundary, but in the interior. The values of sigma_k & sigma_omega are obtained after the blending functions are calculated. I hope this answers your question. Regards 

Tags 
blending function f1, freestream, kw sst 
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