  The dynamics of cavitation bubbles in the vicinity of a solid cylinder or
fibre are seen in water treatment, demolition and/or cleaning of composite
materials, as well as bio-medical scenarios such as ultrasound-induced bubbles
near the tubular structures in the body. When the bubble collapses near the
surface, violent fluid jets may be generated. Understanding whether these jets
occur and predicting their directions -- departing or approaching the solid
surface -- is crucial for assessing their potential impact on the solid phase.
However, the criteria for classifying the onset and directions of the jets
created by cavitation near a curved surface of a cylinder have not been
established. In this research, we present models to predict the occurrence and
directions of the jet in such scenarios. The onset criteria and the
direction(s) of the jets are dictated by the bubble stand-off distance and the
cylinder diameter. Our models are validated by comprehensive experiments. The
results not only predict the jetting behaviour but can serve as guidelines for
designing and controlling the jets when a cavitation bubble collapses near a
cylinder, whether for protective or destructive purposes.
