Numerical Study of Ultrasound-Induced Bubble Motion Using a CLSVOF Method

Ultrasound-induced bubble oscillation, applicable to various engineering fields such as surface cleaning, biomedical therapy, and water purification, has been widely studied through numerical approaches using level-set (LS) and volume-of-fluid (VOF) methods. Although many numerical studies have employed VOF-based schemes for their volume-conserving advantages, significant mass loss in compressible two-phase flows has been reported due to the inherent limitation of the VOF advection equation, which does not guarantee mass conservation. In this work, we extend a coupled level-set and VOF (CLSVOF) method to compressible multiphase flows by consistently estimating both volume and mass fluxes. The van der Waals equation is applied to the air phase, and the Tait equation is used for liquid water to account for compressibility effects induced by ultrasound pulses and shock waves. To validate the present method, benchmark tests are first performed, and the numerical results are compared with data from previous literature and commercial software. Simulations of ultrasound-driven bubble oscillation are also conducted and compared with numerical solutions based on the Keller–Miksis equation. In addition, bubble dynamics near deformable viscoelastic solids are investigated to explore bubble–tissue interactions.