Figure 5.

Calculations of the transient diffusion of dissolved gases into a bubble excited by a lithotripter shock wave. For each indicated static pressure in the liquid, bubble oscillation and the concomitant diffusion lead to a new equilibrium bubble radius for a given initial radius. The dashed line denotes the locus of points corresponding to zero net diffusion such that initial and equilibrium radii are the same. The plot was generated for comparison with Fig. 3 from Sapozhnikov et al.11 and shows virtually the same results. Calculations utilized the SCL model, neglected vapor transport, assumed an ambient temperature of 20 °C, and assumed an initial concentration of dissolved gases corresponding to equilibrium at a pressure of 1 bar. The lithotripter shock wave was modeled by assuming an instantaneous pressure rise to the shock’s peak positive value p_sw at time t = 0. Following Sapozhnikov et al., subsequent acoustic pressures were modeled as 2p_swe^-αtcos(2πft+π∕3), where p_sw=50 MPa, α=9.1×10⁵ s^-1, and f=83.3 kHz.