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

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.