Froude number dependence of the flow separation line on a sphere towed in a stratified fluid

In this paper experimental results on the near field of the flow past a sphere in a linearly stratified medium are presented. Emphasis is placed on the variation of the flow separation line with internal Froude number F=U/NR and also with Reynolds number Re=2RU/ν, where U and R are, respectively, the velocity and the radius of the sphere, N is the Brünt–Väisälä frequency (rad sec−1 ), and ν is the cinematic viscosity. It is shown that in the Reynolds number range 200 1.5 the flow starts to recover its three-dimensionality.