Learning Forum

[lmyscu2011]

Hi there, 

I am using ANSYS FLUENT to do LES and heat transfer simulation. As far as I know, when turbulent model is used, the conduction term on the right-hand side of energy balance equation should have an effective thermal conductivity, k_eff.

k_eff = k_0 + k_t

k_0 is the molecular thermal conductivity, and k_t is the turbulent thermal conductivity. I cannot find the definition of k_t in FLUENT's manual, but I will need it for my research paper. 

Could you please let me know what the equation for k_eff is when LES turbulent model is used? (i do find definition of k_eff for standard k-epsilon model) 

Thanks,

--Mingyi

[Kalyan Goparaju]

Hello Mingyi,
K_eff remains the same even for LES. k_t (turbulent thermal conductivity) for LES is nothing but the turbulent conductivity of the subgrid scales since they are the only ones that are modeled. This is obtained from the subgrid scale prandtl number for energy, which is by default set to 0.85 (viscous models dialogue box).
Thanks Kalyan