Non-linear relaxation oscillations in liquid hour glass

Abstract

We perform a table-top experiment with an hour glass having two nozzles. The hour glass contains two immiscible liquids, namely water and kerosene. We observe under certain experimental conditions that the nature of flow of one liquid through another is intermittent. This intermittency depends upon the relative densities and surface tensions of the two liquids. The varied nature of flow is observed with the change of surface tension, by adding a red dye in one liquid (water) while the surface tension of the other liquid (kerosene) is kept constant. To have a better understanding we simulate the above phenomena through an analog electronic circuit based on a relaxation oscillator with non-linear feedback. Our study reveals some novel and interesting features associated with the non-linear fluid flow through narrow constrictions under controlled conditions.