Suppressing the jet formation in a bubble pair excited with an ultrasonic pulse.

This study numerically explores the suppression of bubble jet formation in oscillating microbubble pairs under excitation with an ultrasonic pulse, focusing on the conditions that lead to bubble collapse without jetting. Bubble jets (i.e., liquid jets penetrating the bubble) are typically observed in collapsing bubble pairs. However, jet formation can be avoided when the distance between the bubbles is kept within a specific range. We investigate identical-sized bubble pairs aligned along an axis and subjected to a single-cycle ultrasound pulse. Simulations are conducted using the axisymmetric assumption with the ALPACA compressible multiphase flow solver. Our findings revealed that the domain where jet formation is suppressed becomes smaller as the bubble compression increases. This is demonstrated by decreasing the bubble size and the excitation frequency, which allows for greater bubble growth. These results indicate that while jet suppression is feasible for bubble pairs with high compression ratios, it becomes increasingly sensitive to distance.