CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

Governing Equation for Energy in LES ANSYS Fluent

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 28, 2021, 15:09
Smile Governing Equation for Energy in LES ANSYS Fluent
  #1
New Member
 
Wayne
Join Date: Aug 2017
Posts: 2
Rep Power: 0
godiex2 is on a distinguished road
I'm using ANSYS Fluent for some simulations in my dissertation. I wanted to ask about the energy equation used when running LES with incompressible fluid, no mixing or reaction. I found the energy equation listed in the ANSYS Fluent Theory Guide (in 5.2.1 Heat Transfer Theory) but I can't find the details about the turbulent thermal conductivity (k_t). Can anyone please link me to it if I missed it?

Is there a filtered form of the energy equation for LES in ANSYS Fluent? A link to that would be much appreciated.
godiex2 is offline   Reply With Quote

Old   June 28, 2021, 15:55
Default
  #2
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 4,388
Rep Power: 52
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
The turbulent conductivity you get from the turbulent Prandtl number which you can find as a setting. Specifically for LES though, this is the turbulent Prandtl number for the subgrid scales only since the filtered scales are resolved.

Of course a closure model has already been invoked. In general, it would be a turbulent heat flux which you can write other ways (not using turbulent conductivity). The filtered energy equation looks identical except you have filtered variables instead of normal variables and subgrid variables instead of turbulent variables, i.e. ksgs instead of kt. There is an ubiquitous notation clash here since ksgs is also the subgrid kinetic energy (instead of subgrid thermal conductivity).
LuckyTran is offline   Reply With Quote

Old   June 30, 2021, 13:39
Default
  #3
New Member
 
Wayne
Join Date: Aug 2017
Posts: 2
Rep Power: 0
godiex2 is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
The turbulent conductivity you get from the turbulent Prandtl number which you can find as a setting. Specifically for LES though, this is the turbulent Prandtl number for the subgrid scales only since the filtered scales are resolved.

Of course a closure model has already been invoked. In general, it would be a turbulent heat flux which you can write other ways (not using turbulent conductivity). The filtered energy equation looks identical except you have filtered variables instead of normal variables and subgrid variables instead of turbulent variables, i.e. ksgs instead of kt. There is an ubiquitous notation clash here since ksgs is also the subgrid kinetic energy (instead of subgrid thermal conductivity).
Thank you for the response!
May I ask the relation between the effective Prandtl number and the turbulent Prandtl number?
godiex2 is offline   Reply With Quote

Old   October 6, 2021, 14:04
Default
  #4
New Member
 
Wojciech Gołda
Join Date: Nov 2020
Posts: 10
Rep Power: 2
Golaselo is on a distinguished road
Quote:
Originally Posted by godiex2 View Post
Thank you for the response!
May I ask the relation between the effective Prandtl number and the turbulent Prandtl number?
Hello godiex, did you find out solution about turbulen heat flux?
Golaselo is offline   Reply With Quote

Reply

Tags
energy equation, governing equation, heat transfer, les

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
ANSYS fluent and OpenFoAM comparison gentodin Main CFD Forum 6 February 26, 2021 03:58
Domain Reference Pressure and mass flow inlet boundary AdidaKK CFX 75 August 20, 2018 05:37
How to open Icem mesh in Ansys Fluent? emmkell FLUENT 27 February 6, 2018 03:34
A question about LES in 2D Fluent tjushang FLUENT 3 September 26, 2014 03:35
What the differences flow equation of Fluent 6.3 and Fluent 12.1 opehterinar81 FLUENT 0 August 19, 2011 11:55


All times are GMT -4. The time now is 05:25.