End-Wall Flow of a Surface-Mounted Obstacle on a Convex Hump

Abstract

A convex hump has been used to overcome the undesirable effects of the juncture vortex. The effects of a convex hump on the approach boundary layer and consequentially the end-wall flow were quantified. A convex geometry imposed a favorable pressure gradient on the boundary layer, reducing the turbulence intensities and the total kinetic energy of the flow. Increased radius of curvature resulted in a more favorable pressure gradient. A combination of these effects has been shown to delay flow separation and reduce the affected area of the juncture vortex on the surrounding flow. Both laminar and turbulent flows were analyzed for four convex humps of different curvature. Particle Image Velocimetry (PIV) has been conducted in a water tunnel along with Planar Laser Induced Fluorescence (PLIF) to quantify the stream-wise two-dimensional properties of the system. Surface flow visualization and surface pressure measurements were conducted in the wind tunnel to define time-averaged turbulent surface effects. As the pressure gradient became more favorable due to convex curvature, the primary singular point of separation formed closer to the leading edge of the obstacle. The vortices presented themselves in a more compact configuration as radius of curvature was increased. The increased streamline displacement associated with increasing radius of curvature, flattened the vortex increasing vorticity and strain in the juncture region. The bifurcation point moved downwards closer to the surface reducing the area of influence of the system. Increased vortical activity was Reynolds number dependant, the physical location of singularities were dependent on curvature geometry.