The recovering boundary layer downstream of a separation bubble is known to
have a highly perturbed turbulence structure which creates difficulty for
turbulence models. The present experiment addressed the effect of this pert
urbed structure on turbulent heat transport. The turbulent diffusion of hea
t downstream of a heated wire was measured in a perturbed channel flow and
compared to that in a simple fully developed channel flow. The turbulent di
ffusivity of heat was found to be more than 20 times larger in the perturbe
d flow. The turbulent Prandtl number increased to 1.7, showing that the tur
bulent eddy viscosity as affected even more strongly than the eddy thermal
diffusivity. This result corroborates previous work showing that boundary l
ayer disturbances generally have a stronger effect on the eddy viscosity, r
endering prescribed turbulent Prandtl number models ineffective in perturbe
d flows.