On a turbulent wall jet flowing over a circular cylinder

Abstract

The effect of surface curvature on the development of a two-dimensional wall jet was investigated experimentally. A comparison was made between a wall jet flowing around a circular cylinder and its plane equivalent. Velocity surveys and surface pressure measurements in the curved wall jet suggest the existence of two primary regions of interest. The first region, ranging from the end of the potential core to an approximate angular position of θ=120°, is characterized by a constant surface pressure and a self similarity of the mean flow. The second region is marked by an adverse pressure gradient leading to separation around θ=230°. The rate of spread of this flow, even in the initial region, is much higher than in the plane wall jet and so are the levels of turbulence and Reynolds stress. The dominant lengthscale in this flow is the radius of curvature R and the dominant velocity scale is the square root of the kinematic jet momentum divided by the radius of curvature. Entrainment of ambient fluid which causes the jet to adhere to the curved surface is also the main reason for its separation which is preceded by a rapid rate of spread of the flow leading to the failure of the boundary-layer approximation.