Spatially advancing turbulent flow and heat transfer in a curved channel at friction-velocity-based Reynolds number 550

The flow and heat transfer in a curved channel were numerically analyzed for their spatial advancement under the influence of streamline curvature. The simulation was made for the curved channel of the radius ratio 0.92. The curved channel was provided with the fully developed velocity and thermal profile in a straight channel at the mean velocity Reynolds numbers up to 20,400. The number of grid points was more than 3.00 × 10 8 for the case of the highest Reynolds number. The local Nusselt number indicated that the heat transfer was enhanced on the outer wall of the curved channel and such enhancement was notable over the downstream area of ϕ ≧ 80°. This heat transfer enhancement came from the large-scale organized vortex which intensified the lateral convection of the secondary stream and caused high values of the turbulent heat flux. The pre-multiplied spectrum was used to analyze the spatial advancement of the large-scale organized vortex. The spectrum indicated that the large-scale vortex was produced from the initial disturbance in the straight channel and the vortex grew and expanded to nearly the channel full width. It was shown that the advancement of the vortex was almost independent from the Reynolds numbers.