Experiments on annular liquid jet instability and on the formation of liquid shells.

Abstract

An annular jet flow of liquid surrounding a flow of gas at its core is extremely unstable. Experiments are described in which such a flow was generated by an annular nozzle operated at fairly specific conditions. It is shown that periodic, axisymmetric oscillations arise spontaneously within the cylindrical sheet emerging from the nozzle and grow with such rapidity along the axial dimension, that a sealing off and encapsulation of the core gas occurs within a few jet diameters. This is closely followed by a pinch-off of the liquid between adjacent bubbles. The liquid shells set free assume spherically symmetric form under capillary forces and each contains a precisely uniform measure of gas and liquid on account of the extremely high frequency stability of the process. Description is given of the fluid dynamic processes by which the shells are formed and mention is made of exploiting the instability for the production of rigid shells for technological applications. (A)