Anisotropic growth dynamics of liquid bridge during droplet coalescence under acoustic levitation

Coalescence of droplets is connected to fascinating interfacial fluid dynamics that is of great importance in a variety of natural and engineering systems. We here explore the growth dynamics of liquid bridges during droplet coalescence under acoustic levitation. We show that the early-time evolution of the liquid bridge follows a scaling law $d\ensuremath{\sim}{t}^{5}$ in the inertial regime, with different prefactors for horizontal and vertical growth. We also highlight the interplay between acoustic radiation pressure and Laplace pressures. A new dimensionless parameter, the Acoustic-Capillary Dynamics Number, is introduced to enhance our understanding of liquid bridge dynamics in acoustic fields.