The effect of tip bluntness on flow around a slender body of revolution at incidence

The influence of tip bluntness on the dynamics of the flow around a slender body of revolution at high incidence is numerically studied. Six different blunted tip configurations with tip radii of R = 0.01D to R = 0.25D, where D is the body diameter, were tested and compared to the sharp tip configuration at angles of attack of 40° and 60°. The level of tip bluntness determines the type of crossflow separation across both tested angles of attack; separation changes from local separation in the case of the sharp tip or slightly blunted tip (R = 0.01D) to global (characterized by a horseshoe vortex system) with the more blunted tips. The flow over the afterbody is strongly dependent on the angle of attack. For all body configurations at the lower angle (40°), the flow is asymmetric but steady (reverting to a symmetric state after disturbance removal). At 60°, the flow over the cylindrical afterbody for all seven configurations is unsteady, non-stationary, and oscillatory due to crossflow vortex shedding, with a significantly large side force root mean square. Upon removal of disturbances, the flow around the bodies remains unsteady, nonstationary, and oscillatory; the side force acting on the sharp tip configuration oscillates symmetrically around zero mean, whereas the side force acting on the blunt tip configurations remains asymmetric. For all configurations, the mean side force variation with the circumferential disturbance location is virtually bistable. The tip primary vortices merge into the vortex shedding zone, preceded by the appearance of breakdown bubbles, across all body configurations.