To be, or not to be... -instabilities on a liquid jet penetrated into a flowing bath-

TL;DR

This study investigates the instabilities and sheath formation of a liquid jet penetrating into a flowing liquid bath, revealing how entrained air influences jet stability and morphology.

Contribution

It provides experimental insights into the formation and breakdown of air sheaths around a liquid jet in a flowing bath, highlighting new instability phenomena.

Findings

Entrained air sheath prevents jet coalescence.

Formation of air 'cap' causes jet elongation.

Sheath breakdown leads to jet destabilization.

Abstract

We conduct a series of experiments with a special interest on a penetration process and instabilities arisen on a liquid jet impinged to a liquid of the same kind flowing in a channel. The impinged jet penetrates into the flowing bath accompanying with entrainment of the ambient immiscible gas, which results in the impinged jet wrapped by the entrained gas as a 'sheath.' This sheath formation enables the impinged jet to survive in the fluid in the channel without coalescing until the entrained-air sheath breaks down. Occasionally a 'cap' of the entrained air is formed at the tip of the penetrated jet, and the jet elongates like a long balloon.