Flow Visualization, Surface Pressure and Velocity Measurements on a Cylindrical Surface with a Bump

Abstract

A cylindrical bump with a spherical free end has been mounted on a cylindrical surface, and flow visualization, surface pressure measurements and the turbulent velocity statistics measurements were performed. The thickness of the turbulent boundary layer was thinner than the bump height at the position of the bump. Slenderness parameter (H/D) of the bump was 1. This setup was a prototype of a typical wall-mounted sensor on aircrafts, therefore it has practical importance. Analysis of the experimental data shows that thickness of the turbulent boundary layer controls the location of separation over the bump. Spherical ending of the bump delays the separation, especially from half height of the bump to the top of the bump. It also affects the strength of trailing vortices created at the free end of the bump, and hence size of the separated region. The thickness of the horseshoe vortices are directly related to the freestream velocity. The curvature of the ground plate does not have significant effect for far downstream positions.