
[Sponsors] 
May 22, 2012, 08:15 
Fluent : turbulence Model

#1 
Member
prince
Join Date: Jun 2011
Posts: 56
Rep Power: 6 
Friends,
I have read many threads in this forum regarding turbulence models. Still i am not very clear with it. I would like to put some thoughts of mine which is making me confused. I will really appreciate any help here.. 1) Can we apply standard kepsilon or RNG or Relizable turbulence model when Y+ = 1 in Fluent ?? I guess we can not apply any variance of kepsilon model when mesh is too fine near the wall. But still would appreciate any comment on this.. 2) Variance of Komega model, as per ANSYS theory guide, uses wall function when coarse grid is used and switch to low Reynolds number model when mesh is very fine near the wall (Y+=1). Which wall function it used ?? In the GUI interface of FLUENT, i can not observe any wall function like i did while using Kepsilon model. As values of Y+ is available to fluent after only few iteration. How does the FLUENT decide whether to use wall function or low Reynolds number model for initial iterations ?? 3) To tackle heat transfer problem, where temperature gradient near the wall is important which model will you suggest. With my logic Kepsilon should ruled out automatically as it does not handle near wall region well. 4) Also, in my opinion low Reynolds number model is the best bet we have for heat transfer problem. But requirement of very fine grid is very much problematic. And i am not able to generate such fine mesh for my complicated geometry involving many solid objects in path of flow and holes in those solid objects for the passage of fluid. 

May 23, 2012, 03:30 

#2  
Super Moderator

Quote:
Quote:
Y+ <= 6 near wall treatment. LRN Y+ > 6 and Y+ < 30 : mix of both through some function. details are given in help Y+ > 30 : SWF Quote:
4) Quote:


May 23, 2012, 07:23 

#3 
Member
prince
Join Date: Jun 2011
Posts: 56
Rep Power: 6 
Thanks Far
You did help a lot.. Although it did not fix my current problem but it will help in long run.. I will try and see what can i do with what i have.. I may post more related to these turbulence model.. Please reply if u can.. Regards.. 

May 24, 2012, 01:09 

#5 
Member
prince
Join Date: Jun 2011
Posts: 56
Rep Power: 6 
I am using GAMBIT for meshing and solving it in FLUENT.
I am trying to adapt the grid where Y+ is large in Fluent but till now with not much success. As geometry is so complex, I have very little control over meshing. I am using unstructured T/Grid mesh in Gambit and doing Volume mesh directly. I have divided my volumes in many small parts and i can mesh them properly, But there is one big volume which contain all other volumes (other volumes are wall and solid objects with holes) is creating problem. This big cylindrical volume i made by using split operation and i do not have any control on meshing this particular volume. I have posted the detail of my geometry in this link Mesh quality and there also i get help from you. But with renew problem of Y+, i am stuck again. If u can provide any suggestion on how to mesh that big volume, it will help a lot. In mean time, i will keep trying. Thanks for all the help.. 

November 25, 2014, 13:22 

#7 
New Member
azna
Join Date: Nov 2012
Posts: 28
Rep Power: 5 
Hi,
I was wondering that are the equations for k epsilon turbulence model different for simulation using Eulerian dispersed multiphase model or VOf multiphase model? Thanks 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
gammaReTheta turbulence model for predicting transitional flows  FelixL  OpenFOAM Programming & Development  79  October 11, 2015 15:30 
How to create a 3Ds Car Model importing to FLUENT?  spysunny  Main CFD Forum  1  January 11, 2012 00:40 
Fluent 12 kw SST turbulence model  DarrenC  FLUENT  0  December 13, 2009 09:33 
two turbulence model in fluent  duaiduaihu  FLUENT  1  August 26, 2009 19:39 
FLuent CAvitation Model requires Turbulence?  CFDtoy  FLUENT  2  January 12, 2007 11:27 