k-w SST freestream values for w
 

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!

Hi,

Were you able to solve this issue ?

wr

Hi Ashwani,

I did manage to proceed ahead.
Can you be more specific?

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

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