6. Von Karman Analogy

Von Karman extended Prandtl’s analogy by separating the flow field into three distinct layers: a viscous sublayer, a buffer layer, and a turbulent core.

In the buffer layer, molecular and eddy diffusivities are assumed to be of the same order of magnitude. \[\boxed {\text{St} = \frac{h}{\rho C_P v_m} = \frac{f}{2}\left(\frac{1}{1+5\sqrt{f/2}\left\{(\text{Pr}-1)+\ln\left[(5\text{Pr}+1)/6 \right]\right\}}\right)}\]