We are hosting the IUTAM Symposium on Dynamics and Interface Phenomena of Bubbles and Droplets at Multiple Scales, to be held in Tokyo, Japan, from Dec 3rd to Dec 5th in 2023.
The dynamics of bubbles and droplets are an interesting multiscale phenomenon. On one hand, their motion can induce scales much larger than their size, while, on the other hand, their motion depends on microscopic, interfacial phenomena at the scale of electrons, atoms, and molecules. For example, the change of boundary conditions associated with surfactant molecules at the interface causes drastic changes in the motion of rising bubbles. Likewise affected are bubble-bubble interactions; the coalescence of small bubbles hardly occurs in the presence of surfactant. These factors are coupled and can dramatically change the whole bubbly flow structure. Another example is the acceleration of bubble collapse due to nonequilibrium phase transition at the gas-liquid interface. Thus the microscopic study of gas-liquid interface and the macroscopic study of bubble and droplet dynamics mutually promote the enhancement of knowledge. To understand such multi-scale physics, the topic of the symposium is focused on bubble dynamics, droplet dynamics, and related interface phenomena at gas-liquid interface. Further advancements in both numerical and experimental approaches of multi-scale analysis are strongly needed in several applications. In bubble dynamics, the stability of nanobubbles provides fundamental knowledge for cavitation inception as well as medical applications, where understanding the extremely high pressure and temperature fields induced by violent bubble collapse is likewise necessary. Bubble clustering can alter the macroscopic vortical structures of turbulence, and the coalescence of interfaces and bubble-bubble interactions are keys to understanding the physics. The impact of droplets on various targets involves rich physical phenomena in multiple scales, namely deformation and disintegration of interfaces, pressure buildup in thin air film, shock wave emission, shear stress due to side-jets, and coalescence. Surface nanodroplets are very important for understanding crystal formation of pharmaceutical products. The physics and chemistry in molecular scales is needed for understanding these phenomena. The interface, as well as thin liquid film, possesses the structure in molecular scale. The mass, momentum and energy transfers across the interface, which are inevitably associated with nonequilibrium dynamics of molecules, dominate the motions of fluids separated by it. The investigation of physics, thermodynamics and physical chemistry of interface from molecular to macroscopic scales is therefore indispensable for the aforementioned topics and other applications related to bubbles and droplets.
Shu TAKAGI and Takeru YANO, Co-Chairpersons of the Symposium