Numerical Simulation of Vortex Structures and Heat Transfer behind a Hill in a Laminar Boundary Layer

Abstract

The present study performed three-dimensional numerical simulation of vortex structures and the heat transfer behind a hill mounted in a laminar boundary layer. A vortex pair is symmetrically formed in the separation bubble behind the hill, and a hairpin vortex is periodically shed in the wake. The hairpin vortex moves downstream with time, and the gradient of the head of the hairpin vortex increases. Further downstream, the hairpin vortex is deformed to the Ω shape. In the growing process of the hairpin vortex, secondary vortices of the horn shape grow near the wall. The dissipation rate of temperature fluctuation around the hairpin vortex increases because the heated fluid near the wall is removed to the free stream by Q2 ejection. Heat transfer increases due to the legs of hairpin vortex and secondary vortices. These vortices generate high turbulences in the flow field and also contributes to increases of the Reynolds shear stress and turbulent heat flux.