Effect of spanwise pressure gradient on flow and heat transfer characteristics of longitudinal vortices embedded in a turbulent boundary layer

Abstract

This study numerically investigated the influence of spanwise pressure gradient on heat transfer of a 3D turbulent boundary layer with longitudinal vortices. A 30° bend in the passage provided the spanwise pressure gradient. The longitudinal pair vortices were generated using a pair of delta winglets. The Reynolds-averaged Navier-Stokes and energy equations based on the conventional Reynolds stress model were used. The predictions agreed well with the experimental data for the straight plate. The turbulent boundary layer was significantly perturbed with the longitudinal vortices. The spanwise pressure gradient contributed to faster degradation of the longitudinal vortices and widened the perturbed flow region. The local Stanton number distributions were asymmetric because of the difference in the evolution of the longitudinal vortices in the curved region. Moreover, comparison showed that the local Stanton number in the downstream of the straight channel increased near the surface because of the secondary re-circulating vortex. The thickness of the thermal boundary layers increased in the streamwise direction because of the significant flow mixing and heat transfer.