Oscillation and levitation of balls in continuously stratified fluids
Abstract
The free motion of balls is investigated experimentally in continously stratified fluid in a finite container. The oscillation frequency is found to be very close to the local Brunt-Vaisala frequency. The effect of added mass proves to be practically negligible. The evolution of rear jets is demonstrated, and a kind of long term levitation is found. We show that the classical viscous drag would lead to a much stronger damping than observed in the experiment. This is interpreted as a consequence of the feedback from the previously excited internal waves following their reflection from the boundaries. A phenomenological equation with a modified drag term is proposed to obtain a qualitative agreement with the observations. We point out that the inclusion of a history term would lead further away from the observed data.
Cite
@article{arxiv.physics/0702208,
title = {Oscillation and levitation of balls in continuously stratified fluids},
author = {I. Biro and B. Gyure and I. M. Janosi and K. G. Szabo and T. Tel},
journal= {arXiv preprint arXiv:physics/0702208},
year = {2008}
}