The impact and penetration of a water surface by a liquid jet

It is well known that a high velocity jet threads a spherical bubble during asymmetric collapse. The early phases of jet formation and travel have been investigated by several workers. The final stage of collapse, in which a microjet impacts on the rear wall of the cavity and penetrates it are less well studied and difficult to model accurately. A series of experiments were thus conducted in which liquid jets of varying velocity were fired at semi-infinite water targets. The penetration was monitored using high-speed streak and framing photography. An unexpected feature of the penetration was found to be the appearance of an axial cavitation cloud ahead of the jet. This cloud was subsequently collapsed by what is believed to be an entrapped air bubble collapsing at the jet-target interface. The subsequent motion of this interface showed periodic acceleration and deceleration. The results have interest to a range of practical situations involving cavities and their collapse.