Bubble dynamics in a pressure gradient with reentrant jet break through and energy loss.

The dynamics of a bubble in a pressure gradient is investigated experimentally and numerically with particular emphasis on the behavior at reentrant jet impact and break through the opposite side of the bubble with corresponding energy loss and vorticity generation. High speed photography observations of a bubble generated by electric spark energy deposit in a low ambient pressure tank are coupled with wavelet based Optical Flow Velocimetry (wOFV) and Boundary Element Method (BEM) numerical analysis to examine the flow field resulting from the reentrant jet formation and break through. We study, as an illustration, the effects of the constant pressure gradient due to gravity on the bubble dynamics. Energy losses between the first and second cycle are measured for the bubbles generated under various conditions characterized by a non-dimensional pressure gradient parameter, and the corresponding measured energy loss is used in the numerical simulations. Good correspondence is seen between the image analysis, the wOFV computations, and the BEM results and insight is gained on the involved physics.