On a turbulent wall jet flowing over a circular cylinder

The effect of surface curvature on the development of a two-dimensional wal l 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 th e existence of two primary regions of interest. The first region, ranging f rom the end of the potential core to an approximate angular position of the ta = 120 degrees, is characterized by a constant surface pressure and a sel f similarity of the mean flow. The second region is marked by an adverse pr essure gradient leading to separation around theta = 230 degrees. 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 d ivided by the radius of curvature. Entrainment of ambient fluid which cause s the jet to adhere to the curved surface is also the main reason for its s eparation which is preceded by a rapid rate of spread of the flow leading t o the failure of the boundary-layer approximation.