Research Article

Driven oscillations of a curved object under a laminar jet of water

ENS de Lyon, 69342 Lyon, France

^* e-mail: lea.delance@espci.fr

Received: 27 September 2019
Accepted: 3 August 2020

Abstract

By putting a ball on a flat surface under a jet of water, one may observe spontaneous oscillations of the ball of well-defined amplitude and frequency. As a simpler conformation, the study of a cylinder shows that the mere effect of the jet is sufficient to observe an oscillation for a certain range of parameters such as the curvature of the object and the characteristics of the jet. An empirical model of the forces strengthened by direct measurements of the forces and torque allowed us to predict a theoretical period of 0.64 s when the experimental one was 0.80 s. Further, the origin of the oscillation was determined to be a dynamic hysteresis of the torque as it is deflected on one side of the can even when the jet hits its center. This phenomenon results in a gain of energy that counterbalances the losses by friction and leads to oscillations. Domain of oscillation is also shortly addressed while improvements of the theoretical model and other experiments are suggested as well.