Turbulent heat flux in k-epsilon and k-omega

Golaselo · October 6, 2021, 15:33

Hello everyone,

could anyone help me with turbulent heat flux in k-epsilon and k-omega? I have simple 2D flow in pipe and I would like to include turbulent heat flux in my energy equation. What whould I do, I am a bit beginner in CFD world.

Thanks a lot for help.

LuckyTran · October 6, 2021, 16:14

How are you approaching the flow part? Do you have the laminar energy equation working already?

Really you just replace the thermal conductivity with an effective conductivity using a turbulent Prandtl number. That means you also need a working turbulence model for turbulent viscosity as well. So, the challenge is everything but the energy equation.

Golaselo · October 6, 2021, 16:21

I am using standard energy equation from Fluent in Ansys. Turbulent heat flux is not included in it. I use two turbulence models k-e and k-w. I didnt change anything else in these models. So I have to modify my wnergy equation and include turbulence heat flux. Can i use udf to do it ?

LuckyTran · October 6, 2021, 16:36

If you are using Fluent + any turbulence model in viscous model options (i.e. not inviscid and not laminar) then it definitely has a turbulent heat flux and you do not need to do anything.

Sorry I was under the impression that you were working on your own CFD code. I don't know why I would think a beginner would be doing that. Silly me. If only there was an entire forum dedicated to Fluent. :s

Golaselo · October 6, 2021, 16:53

So, when I use any of turbulence models, energy equation is automaticly modified and turbulence heat flux is added to it, am I correct? I mean equation number 5 from that:
https://www.epj-conferences.org/arti...2014_02063.pdf

Really appreciate your help, thanks!

October 6, 2021, 15:33	Turbulent heat flux in k-epsilon and k-omega	#1
Golaselo New Member Wojciech Gołda Join Date: Nov 2020 Posts: 16 Rep Power: 6	Hello everyone, could anyone help me with turbulent heat flux in k-epsilon and k-omega? I have simple 2D flow in pipe and I would like to include turbulent heat flux in my energy equation. What whould I do, I am a bit beginner in CFD world. Thanks a lot for help.

October 6, 2021, 16:36		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	If you are using Fluent + any turbulence model in viscous model options (i.e. not inviscid and not laminar) then it definitely has a turbulent heat flux and you do not need to do anything. Sorry I was under the impression that you were working on your own CFD code. I don't know why I would think a beginner would be doing that. Silly me. If only there was an entire forum dedicated to Fluent. :s sbaffini likes this.

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October 6, 2021, 16:14		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	How are you approaching the flow part? Do you have the laminar energy equation working already? Really you just replace the thermal conductivity with an effective conductivity using a turbulent Prandtl number. That means you also need a working turbulence model for turbulent viscosity as well. So, the challenge is everything but the energy equation.

October 6, 2021, 16:21		#3
Golaselo New Member Wojciech Gołda Join Date: Nov 2020 Posts: 16 Rep Power: 6	I am using standard energy equation from Fluent in Ansys. Turbulent heat flux is not included in it. I use two turbulence models k-e and k-w. I didnt change anything else in these models. So I have to modify my wnergy equation and include turbulence heat flux. Can i use udf to do it ?

October 6, 2021, 16:53		#5
Golaselo New Member Wojciech Gołda Join Date: Nov 2020 Posts: 16 Rep Power: 6	So, when I use any of turbulence models, energy equation is automaticly modified and turbulence heat flux is added to it, am I correct? I mean equation number 5 from that: https://www.epj-conferences.org/arti...2014_02063.pdf Really appreciate your help, thanks!