The near-wake of an inclined 6:1 prolate spheroid in a stratified fluid

A slender body can produce a range of distinct wake geometries, arising from complex 3D flow separations that vary with incidence angle and Reynolds number. Little is known on the effects of background stratification, and how buoyancy affects the near- and intermediate wake. Here, an experiment is conducted on the wake of a 6:1 spheroid in both uniform and stratified backgrounds. The inclination angle is varied from 0° - 20°. Reynolds numbers, Re_D = {0.5, 1, 2} × 10⁴ and Froude numbers, Fr ={16, 32, 64, ∞ } are tested. Both stereo-PIV (2D3C) and tomo-PIV (3D3C) are used to visualize the flow. When the body is at incidence, the wake is formed from a combination of the usual drag wake together with coherent streamwise vortices, and this wake geometry can evolve in ways that are measurably different from the zero incidence case. In the presence of density stratification, the inclined wake itself generates large-scale internal wave undulations, even at relatively weak background stratification.