Eddy diffusivity of heat transfer
A quantity characterizing the intensity of turbulent heat transfer, defined by the identity
is the turbulent heat flux density (i.e., the heat flux due to turbulent transfer) over a certain unit area in the flow; ρ
is the density; wy
' is the fluctuation of the transverse (with respect to the area element) component of the velocity vector; T'
is the fluctuation temperature; cp
is the heat capacity of the fluid at constant pressure; ∂T
is the derivative with respect to the normal to the area element of the (time) averaged value of the temperature.
The term is defined by assuming that fluctuations of the physical properties can be neglected.