Numerical study of ultrasonic bubble cavitation and viscoelastic solid deformation

Ultrasonic bubble cavitation, which induces considerable deformation of nearby solids by forming shock waves and high-speed liquid jets, has been applied to various engineering fields such as surface cleaning, medical therapy, and water purification. In this work, numerical study of ultrasound-driven bubble cavitation and solid deformation is performed by employing a full Eulerian method for effectively computing the fluid flow and solid deformation and a level-set method for tracking the bubble-water and water-solid interfaces. We use the Van der Waals equation for gas and Tait equation for liquid and solid to consider the compressibility effect of an ultrasonic pulse and shock wave, and a neo-Hookean model to include the elastic feature of solid. The present method for solid deformation is validated by comparing the numerical predictions of solid disk deformation in a lid-driven cavity with the results reported in the literature. Ultrasound-driven bubble motion and solid deformation patterns are analyzed according to the bubble-solid stand-off distance and the elastic shear modulus. The effect of the solid impedance on the shock wave pressure and liquid jet velocity inducing cavitation pits was further investigated by varying the bulk modulus and density of the solid.