The Gallery of Fluid Motion is one of the most enjoyable aspects of the American Physical Society’s Division of Fluid Dynamics conferences. Although I had long admired the creativity of the entries, I never found the time to create a poster or video worthy of submission. In 2016, I devoted a significant effort to capturing a phenomena under investigation, and submitted a poster, which was one of the winners of the 2016 APS/DFD Gallery of Fluid Motion award winners in the poster category.
A train of vapor bubbles is formed by ejection into a subcooled liquid pool. In the base flow, surface tension pinch-off drives a liquid “spear” through the center of the vapor bubble to form a vapor torus that leads to rapid condensation. Alternatively, using a directed 1.7 MHz pulsed acoustic beam early in the vapor bubble formation (and prior to pinch-off) exploits the liquid-vapor acoustic impedance mismatch to force a similar liquid “spear,” forming a vapor torus and accelerating the bubble collapse.
Accelerated Condensation in an Ultrasonic Field