Unsteady flow around an ogive cylinder

The time-dependent flow around ah ogive cylinder undergoing large-amplitude, harmonic pitching motion was investigated using flow visualization techniques. The slender body of revolution was towed in an 18 m water channel at Reynolds numbers up to 1.2xl0. Fluorescent dyes were either introduced uniformly from the body's porous surface or placed as horizontal sheets in the slightly stratified tank prior to a run. The dyes were excited with a sheet of laser light projected in the desired plane to mark the flow in the separation region around the body, the flow in the wake, and the potential flow away from the body. The separation process and the geometry of the leeward vortices were studied under different reduced frequencies and Reynolds numbers. The unsteady separation phenomenon is found to be significantly different from the separation on a body in steady flight. Two distinct separation regions, the forebody and aftbody vortex pairs, evolve in the unsteady case.