Falling Spheres in Sharply Stratified Fluids*

We explore the motion of heavy spheres falling through a sharp salt stratified fluid layer in which an intriguing levitation phenomena is observed: the heavy sphere experiences a transient levitation in which the sphere descends through the sharp transition, stops, and rises back into the layer before ultimately returning to descent. Careful new measurements will be presented showing how the bounce amplitude depends upon layer thickness. The hydrodynamics, which involves a strong coupling between variable density fluid, and moving solid boundary, entrained, turbulently mixed fluid, and strong internal waves will be discussed. We will discuss exact and asymptotic calculations in potential flows yielding the potential energy associated with the sharp interface which may provide an arrestment criteria for the falling sphere.