OpenFOAM: Variable Turbulent Prandtl Number

kakkapriyesh · May 18, 2021, 05:07

Hello,

I had modified the OpenFOAM solver to see the effects of turbulent Prandtl numbers on the heat transfer near the wall (dynamic Smagorinsky | LES). For incompressible solver, OpenFOAM keeps turbulent Prandtl number as constant, hence energy equation solved is not truly dynamic. I calculated turbulent Prandtl number using test filters similar to dynamic models referring to Lilly's paper of 1992. Here, the turbulent Prandtl number is calculated at every timestep, and it influences the energy equation.

Please find the solver Github link for more details:
https://github.com/kakkapriyesh/Vari...umber_OpenFOAM

I hope this code is useful to someone!

Tian Hongkang · November 20, 2021, 22:26

Quote:

Originally Posted by kakkapriyesh

Hello,

I had modified the OpenFOAM solver to see the effects of turbulent Prandtl numbers on the heat transfer near the wall (dynamic Smagorinsky | LES). For incompressible solver, OpenFOAM keeps turbulent Prandtl number as constant, hence energy equation solved is not truly dynamic. I calculated turbulent Prandtl number using test filters similar to dynamic models referring to Lilly's paper of 1992. Here, the turbulent Prandtl number is calculated at every timestep, and it influences the energy equation.

Please find the solver Github link for more details:
https://github.com/kakkapriyesh/Vari...umber_OpenFOAM

I hope this code is useful to someone!

Thank you for sharing.
I recently want to make a simulation of liquid metal flow in a circular tube with buoyantSimpleFoam. I know how to define the turbulence Prandtl number at the wall, but I don't know in which dictionary file to define the global turbulence Prandtl number and change it to my turbulence Prandtl number model. I would be very grateful if you could give me some advice.

kakkapriyesh · November 21, 2021, 00:04

I am not sure what you mean by global turbulence prandtl number, as far as I remember, turbulent prandtl number was kept as a constant throughout the field in openfoam as 0.85 i think. I dont remember where that constant is (havent been using openfoam for 2 years) but may it is in some equation probably Temp!

Tian Hongkang · November 21, 2021, 00:09

Ok, thank you for your reply.

May 18, 2021, 05:07	OpenFOAM: Variable Turbulent Prandtl Number	#1
kakkapriyesh New Member priyesh kakka Join Date: Jan 2018 Posts: 13 Rep Power: 8	Hello, I had modified the OpenFOAM solver to see the effects of turbulent Prandtl numbers on the heat transfer near the wall (dynamic Smagorinsky \| LES). For incompressible solver, OpenFOAM keeps turbulent Prandtl number as constant, hence energy equation solved is not truly dynamic. I calculated turbulent Prandtl number using test filters similar to dynamic models referring to Lilly's paper of 1992. Here, the turbulent Prandtl number is calculated at every timestep, and it influences the energy equation. Please find the solver Github link for more details: https://github.com/kakkapriyesh/Vari...umber_OpenFOAM I hope this code is useful to someone! Teresa Sun and Tian Hongkang like this. Last edited by kakkapriyesh; May 20, 2021 at 23:55. Reason: Forgot to mention, this is for LES (dynamic smagorinsky)

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November 21, 2021, 00:04		#3
kakkapriyesh New Member priyesh kakka Join Date: Jan 2018 Posts: 13 Rep Power: 8	I am not sure what you mean by global turbulence prandtl number, as far as I remember, turbulent prandtl number was kept as a constant throughout the field in openfoam as 0.85 i think. I dont remember where that constant is (havent been using openfoam for 2 years) but may it is in some equation probably Temp!

November 21, 2021, 00:09		#4
Tian Hongkang New Member Outside North America Join Date: Nov 2021 Posts: 14 Rep Power: 4	Ok, thank you for your reply.