
[Sponsors] 
January 24, 2012, 21:32 
Turbulent heat flux through the wall

#1 
Member
Yuri Feldman
Join Date: Mar 2011
Posts: 30
Rep Power: 8 
Dear forum,
I am really confused about how I should compute heat flux through the static boundary in the presence of turbulent incompressible flow if I use the basic ke model. According to the heat transfer theory Q''=(k_lam+k_turb)(dT/dn), where k_lam is a some constant value of a certain fluid and k_turb=cp*miu_t/Pr_t. It looks like everything is clear : cp is known, the commonly used value of Pr_t is 0.85, miu_t is calculated from ke model. The twist is that the boundary value of miu_t (niu_t for incompressible flow) is set to zero (I am talking about buouantBoussinesqPimpleFoam tutorial for hotRoom). The same is done for the boundary value of miu_t in Fluent. Then it is completely unclear what is the difference between calculating of heat flux for laminar and turbulent flows. I will be very grateful if somebody clarifies this issue, many thanks, Yuri 

January 25, 2012, 14:34 

#2 
Member
Yuri Feldman
Join Date: Mar 2011
Posts: 30
Rep Power: 8 
please anybody can say his opinion,
I really need your help Last edited by feldy77; January 25, 2012 at 18:59. 

January 25, 2012, 18:50 

#3  
Member

k_turb
Quote:
And the temperature relies on the turbulent model you included although you will have the same gradient at the wall. I am sure temperature in the bulk is totally different between laminar and turbulent flows due to the different heat transfer coeff in the bulk.
__________________
Kai 

January 25, 2012, 19:04 

#4 
Member
Yuri Feldman
Join Date: Mar 2011
Posts: 30
Rep Power: 8 
Kai,
Thank you for your reply. Maybe you can explain me then, why the openFoam utility wallHeatTransfer utilizes alafaeff whcich consists of turbulent amd laminar components and not jus uses the laminar component only Many thanks, yuri 

January 25, 2012, 19:21 

#5 
Member

It is all dependent on the expectation you have. The wall viscosity should be modelled actually. I can only say that the treatment of zero wall viscosity is rather crude. If you would like to model wall viscosity, plz refer to the file "wallViscosity.H" in the solver of bubbleFoam.
__________________
Kai 

March 6, 2012, 08:33 

#6  
Senior Member
Goutam Saha
Join Date: Dec 2011
Location: UK
Posts: 131
Rep Power: 7 
Quote:
Looking forward to see your reply. 

March 6, 2012, 14:33 

#7 
Senior Member
A_R
Join Date: Jun 2009
Posts: 120
Rep Power: 9 
Dear Foamers
for kepsilon model, you must use wallfunction for nut. and without it, the solution is not acceptable. 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Natural convection in a closed domain STILL NEEDING help!  Yr0gErG  FLUENT  3  June 12, 2013 02:12 
HELP  Wall Heat Flux CFX  Karkoura  CFX  5  March 29, 2011 12:44 
calculation of wall heat flux in CHT  richard  CFX  1  July 23, 2009 09:00 
Heat flux and ke wall boundary conditions  Blob  CFX  4  June 8, 2009 05:10 
WALL HEAT FLUX  tommy  CFX  0  December 20, 2005 13:42 