Shear instability of an axisymmetric air-water coaxial jet

TL;DR

This paper investigates the shear instability of an axisymmetric air-water jet, combining experimental measurements and linear stability analysis to identify destabilization mechanisms and develop predictive criteria.

Contribution

It introduces a comprehensive analysis of shear instability mechanisms in coaxial jets, including experimental validation and scaling laws for different destabilization regimes.

Findings

Identified three destabilization mechanisms: convective, surface tension-driven absolute, and confinement-driven absolute instabilities.

Developed scaling laws for wave frequency in each instability regime.

Proposed criteria to predict transitions between different instability regimes.

Abstract

We study the destabilization of a round liquid jet by a fast annular gas stream. We measure the frequency of the shear instability waves for several geometries and air/water velocities. We then carry out a linear stability analysis, and show that there are three competing mechanisms for the destabilization: a convective instability, an absolute instability driven by surface tension, and an absolute instability driven by confinement. We compare the predictions of this analysis with experimental results, and propose scaling laws for wave frequency in each regime. We finally introduce criteria to predict the boundaries between these three regimes.