|
The motion of sphere's falling under the influence of gravity is a
classical problem dating back to Galileo and earlier. How a falling body additionally interacts with its environment is an equally challenging problem and generally requires the complete integration of the Navier-Stokes equations coupled to a moving boundary. Mathematical challenges in implementing an effective solution scheme are limited by issues of resolution needed to resolve the often turbulent fluid motion surrounding the body, and problems associated with discretizing the stiff boundary. Recently, a team of researchers at North Carolina, including two then math undergraduate majors, discovered a new phenomena concerning falling bodies in stratified fluids. Namely: they found that a falling body doesn't just fall, but rather, it may undergo a transient levitation phenomena in which the body stops as it passes through the transition layer, and in fact rises back through the layer, before ultimately returning to descent. This work is published at the physics of fluids (link to paper below), and documents the phenomena along with characterizing the physics responsible for this surprising motion, and presents a minimal (from degree of freedom perspective) dynamical system which captures the motion. Current experimental, theoretical, and computational studies are focussed upon improved measurements, and theoretical predictions of this surprising phenomena. These studies will hopefully form a case study for the benchmarking of constantly improving computational fluid dynamics simulations. |