# k-w SST freestream values for w

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 October 27, 2015, 06:29 k-w SST freestream values for w #1 New Member   Syed Aaquib Hazari Join Date: Apr 2015 Location: Delft Posts: 16 Rep Power: 4 Dear all, I want to know the freestream values of the blending function for 'w' in k-w SST. Additional details: I am trying to simulate the k-w 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 k-w is switched on) & 0 for freestream values (implying k-e 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: 112 Rep Power: 6 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: 4 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: 112 Rep Power: 6 Hi, How is the values of blending function calculated at the boundary faces. The value of sigma_k , sigma_omega in diffusion term of k-omega 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: 4 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, k-w sst

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