Air-cushioning effect and Kelvin-Helmholtz instability before the slamming of a disk on water

Abstract

A solid plate about to slam onto a water surface makes it presence felt before the actual contact by squeezing out a mediating air cushioning layer. This air cushioning layer has regions of low and high pressures. At the point of high (stagnation) air pressure, the water surface is deflected away from the impactor. While in the low pressure region, a Kelvin-Helmholtz instability initiates the suction of the water surface towards the impactor. Using a new measuring technique we measure such deflections, of the order of 10-300 microns, and explain the mechanisms driving them.

Topics & Concepts