Learning Forum

[david.bacci]

Hi all

I am using ANSYS FLUENT to model heat transfer in a pipe with a low Pr gas

Since the typical constant value of turbulent Prandtl = 0.85 is no longer valid in this situation, a custom UDF must be built

I noticed that there are several DEFINE_PRANDTL UDFs, but I suppose the one I must target is DEFINE_PRANDTL_T

However, it seems that it is not doing exactly what I am telling him to do

Is there a way to directly modify the turbulent conductivity or diffusivity, such as making it possible for turbulent viscosity?

Thanks 

David

[Rajat Chaudhari]

H David,

Fluent uses turbulent Prandtl number and turbulent viscosity value to calculate turbulent thermal conductivity part of effecttive conductivity.

You can use DEFINE_PRANDTL and DEFINE_TURBULENT_VISCOSITY function to define it. To access turbulent thermal conductivity you can use  C_K_T(c,t,prt) macro.