
[Sponsors] 
July 13, 2015, 12:55 
Plotting of normal stresses from ke model

#1 
New Member
.
Join Date: Jul 2015
Posts: 2
Rep Power: 0 
i would like to ask as to how to plot the normal stresses for the kepsilon model in fluent? I am assuming that the flow is isotropic and also that i will have to use the boussinesq relationship. However im not sure as to how to actually calculate them.


July 15, 2015, 06:31 

#2 
Senior Member
B_Kia
Join Date: May 2014
Location: Ir
Posts: 123
Rep Power: 9 
hi,as far i know stresses are modeled in ke model , stresses are available in RSM


July 15, 2015, 11:39 

#3 
Senior Member
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,389
Rep Power: 52 
I'm also trying to do the same calculation but haven't come up with a solution yet.
Note that the stresses are not isotropic, only the turbulent viscosity is isotropic. It's incorrect to say the turbulence is isotropic (since u' is not the same as v' and w'). This is very important point. I think you would have to compute the stresses from the boussinesq model from the shear and strain. But again I haven't done this part yet. Maybe in a few days or if someone else is able to post the solution. Last edited by LuckyTran; August 3, 2015 at 17:38. 

August 14, 2015, 06:11 

#4  
New Member
.
Join Date: Jul 2015
Posts: 2
Rep Power: 0 
Quote:
I may have completely misunderstood everything and would be more than happy to be corrected. Last edited by Bubblyflow; August 14, 2015 at 06:13. Reason: forgot to quote 

August 14, 2015, 17:18 

#5  
Senior Member
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,389
Rep Power: 52 
Quote:
I ended up using custom field functions. The eddy viscosity hypothesis assumes that the turbulent viscosity is isotropic. It does not assume that the flow is isotropic or that the uu,vv,ww stresses equal. This is a common misconception. The assumption is that the functional relation between the strain and reynolds stresses is isotropic, whereas both the strain and reynolds stresses can be anisotropic. If you load the attached file, plz be careful as these are the proper stresses with density included. I usually compute only uu,vv,ww without the density. 

Tags 
boussinesq model, epsilon, kappa, stresses 
Thread Tools  Search this Thread 
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Is it possible to model natural convection in a 2D horizontal model in fluent  caitoc  FLUENT  1  May 5, 2014 13:32 
about Subgridscale model  impecca  OpenFOAM Running, Solving & CFD  4  December 20, 2013 10:36 
Low Reynolds kepsilon model  YJZ  ANSYS  1  August 20, 2010 13:57 
LES and combustion model  Margherita Cadorin  CFX  0  October 29, 2008 05:24 
Advanced Turbulence Modeling in Fluent, Realizable kepsilon Model  Jonas Larsson  FLUENT  5  March 13, 2000 03:27 