Estudo numérico de escoamento transicional sobre placa côncava com perturbações não estacionárias

Abstract

The generation of Görtler vortices is the first stage of the turbulent laminar transition process in a boundary layer flow over a concave surface. These vortices produce distortions both in the velocity profile and in the temperature profile, intensifying the heat transfer rate and the drag coefficient compared to the laminar flow. There are several studies to understand the mechanisms of the formation of Görtler vortices to delay or anticipate their generation to maximize or minimize the effects of these two properties in this type of flow. This work investigates the evolution, structure, and influence of non-stationary disturbances in a boundary layer flow over a concave surface through numerical simulation with high-precision methods. The results show the stationary sub-harmonic mode (0,2) dominates the flow generating the stationary Görtler vortices as the spanwise wavelength and time-frequency increase, otherwise, the fundamental mode (1,1) dominates the flow and generated the unsteady vortices. Non-stationary disturbances delay the appearance of Görtler vortices since the growth rate of the fundamental mode (1,1) decreases when the frequency increases regardless of the transverse wavelength. The heat transfer rate and the drag coefficient for the unsteady vortices are lower than for the steady vortices.