CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

k-w SST freestream values for w

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 27, 2015, 05:29
Default k-w SST freestream values for w
  #1
New Member
 
Syed Aaquib Hazari
Join Date: Apr 2015
Location: Delft
Posts: 16
Rep Power: 11
hazari.aaquib is on a distinguished road
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!
hazari.aaquib is offline   Reply With Quote

Old   March 16, 2016, 01:07
Default
  #2
Senior Member
 
Ashwani
Join Date: Sep 2013
Location: Hyderabad
Posts: 154
Rep Power: 13
AshwaniAssam is on a distinguished road
Hi,

Were you able to solve this issue ?

wr
AshwaniAssam is offline   Reply With Quote

Old   March 16, 2016, 05:16
Default
  #3
New Member
 
Syed Aaquib Hazari
Join Date: Apr 2015
Location: Delft
Posts: 16
Rep Power: 11
hazari.aaquib is on a distinguished road
Hi Ashwani,

I did manage to proceed ahead.
Can you be more specific?
hazari.aaquib is offline   Reply With Quote

Old   March 17, 2016, 00:41
Default
  #4
Senior Member
 
Ashwani
Join Date: Sep 2013
Location: Hyderabad
Posts: 154
Rep Power: 13
AshwaniAssam is on a distinguished road
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
AshwaniAssam is offline   Reply With Quote

Old   March 18, 2016, 04:29
Default
  #5
New Member
 
Syed Aaquib Hazari
Join Date: Apr 2015
Location: Delft
Posts: 16
Rep Power: 11
hazari.aaquib is on a distinguished road
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
hazari.aaquib is offline   Reply With Quote

Reply

Tags
blending function f1, freestream, k-w sst

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Laminar-to-turbulent transition modelling using SST and SST Gamma Theta models ttu004 CFX 3 June 13, 2014 06:43
Turbulent flow at low Mach number robyTKD SU2 5 January 3, 2014 03:18
Scaling omega in SST turbulence model TedBrogan Main CFD Forum 0 January 23, 2013 00:00
strange node values @ solid/fluid interface - help JB FLUENT 2 November 1, 2008 12:04
node values or cell values? aPpA FLUENT 0 November 10, 2006 08:56


All times are GMT -4. The time now is 06:07.