Abstract
In this study, delay times of explosive dual microbubbles are controlled precisely to understand the complex and dynamic phenomenon of dual bubbles interactions. The interactions have been characterized in terms of maximal bubble size, sink/source flow, bubble pressure, and useful work. For DT = 0 μs, dual bubbles are produced simultaneously,and the produced pressures inhibit the growth ofeach other. The sizes of those are slightly smaller than thatof a single bubble. For DT = 2 μs, the pressure generated from the second (right) bubble affects the growth of the first (left) bubble in the beginning and poses the first bubble growth slower than the single bubble. When the first (left) bubble starts to collapse, the surrounding flow field induces a sink flow to promote the growth of the second (right) bubble. As the first (left) bubble rebounds, the peak pressure produced by the rebound leads to a rapid collapse of the second (right) bubble. For DT = 8 μs, the first (right) bubble keeps following the history of the single bubble because there is no influence from the second(right) one. As the first bubble rebounds in the same condition, the volume history of the second bubble drops and deviates from the original track of the single bubble. The dynamics of a high heat flux thermal bubble is constrained by the thermal energy carried on the bubble surface right after the bubble formation because of thermal isolation of vapor. This paper proposes a way by assigning time delays between dual bubbles to effectively transfer energy from one bubble into the other, thus breaks energy limitation that one single bubble can usually carry. Experiment result has demonstrated that the useful work as large as 40% can be transferred from one bubble into the other for the ignition time delay set between 2 and 3 μs in a dual bubble system. At the same time, the total extractable useful work in a dual bubble system is 20% higher than twice that of a single bubble system with the same input heat energy. This phenomenon opens up a new way to transfer or concentrate energies from distributed energy sources with limit energy density into a much higher one for higher power application.