Three dimensional microbubble dynamics near a wall subject to high intensity ultrasound

This paper presents a computational model for simulating three-dimensional microbubble dynamics near a wall when exposed to high intensity ultrasound. While previous studies focused on axisymmetric configurations, my research extends to fully three-dimensional dynamics using the boundary integral method.

We implemented several numerical techniques to handle the violent bubble collapse under high intensity ultrasound. A key innovation is my hybrid approach combining the Lagrangian method with elastic mesh technique to maintain high quality surface mesh, particularly important for resolving the sharp jet surface. The model shows good agreement with the Rayleigh-Plesset equation for spherical bubbles and with axisymmetric models.

The research focuses on microbubble dynamics near a wall with ultrasound propagating parallel to the wall - a configuration where the Bjerknes forces from the ultrasound and the wall are perpendicular to each other. The findings reveal that the bubble system absorbs energy from the ultrasound and transforms the uniform momentum parallel to the wall into a concentrated high-speed liquid jet pointing toward the wall.

Key observations include: the jet direction depends primarily on the dimensionless standoff distance of the bubble from the wall; jets are directed toward the wall when the bubble is close (standoff distance ≤ 1.5) and rotate toward the ultrasound direction as distance increases; at distances of 10 or greater, wall effects become negligible and the jet aligns with the acoustic wave direction. While the ultrasound amplitude doesn’t significantly change jet direction, it does increase jet width and velocity.

This research has important implications for applications in ultrasonic cleaning, sonochemistry, and biomedical ultrasound, where controlled microbubble jetting can be harnessed for therapeutic purposes.