Momentum and heat transport in a three-dimensional transitional wake of a heated square cylinder

The transport of momentum and a passive scalar (temperature) in a three-dimensional transitional wake of a heated square cylinder has been carried out through direct numerical simulations using the lattice Boltzmann method at a Reynolds number R-d = 200 (d is the cylinder diameter) and a Prandlt number of 0.7. The Simulations shows that while momentum and heat are transported by vortical structures, heat is in general more effectively transported than momentum. It is argued that the nature of the structural flow is responsible for the longitudinal heat flux (u theta) over bar being larger than the lateral one (nu theta) over bar in the wake region extending Lip to 45d. It was shown that a gradient transport model Could, to a first-order approximation, be used to model (u nu) over bar but Would be less accurate for modelling (nu theta) over bar. Also the Reynolds analogy between momentum and heat transports is not verified in this flow. The fluctuating temperature field presents thermal structures similar to the velocity structures with, however, a different spatial organization. In addition the analogy between fluctuating turbulent kinetic energy and the temperature variance is relatively well satisfied throughout the wake flow.