Dynamics of a laser-induced bubble near a cylinder within a confined space

The collapse of a laser-induced bubble near a cylinder within a confined space is investigated using high-speed photography and the Kelvin impulse theory. On the basis of an analysis of the liquid flow field and the Kelvin impulse, the effects of bubble–cylinder distance and radius ratio on bubble collapse behavior are investigated. Furthermore, the bubble motion during the first bubble oscillation period is quantitatively explored using the Kelvin impulse theory. The main conclusions of this study are as follows: (1) When the bubble is not restricted by the cylinder, three cases of jets are observed—strong jet, medium jet, and weak jet. When the bubble is restricted by the cylinder, three cases of bubble deformation are observed—fan-shaped collapse, ellipse-shaped collapse, and quasi circular shaped collapse. (2) The cylinder mainly affects the velocity of the surrounding liquid through the term of the point sink, and the bubble–cylinder distance mainly affects the liquid velocity from the bubble. (3) The Kelvin impulse intensity exhibits an exponentially decreasing trend with increasing bubble–cylinder distance, which is in good agreement with the experimentally observed jet velocities.