title: Shock-induced collapse of a gas bubble in shockwave lithotripsy.
abstract: The shock-induced collapse of a pre-existing nucleus near a solid surface in the focal region of a lithotripter is investigated. The entire flow field of the collapse of a single gas bubble subjected to a lithotripter pulse is simulated using a high-order accurate shock- and interface-capturing scheme, and the wall pressure is considered as an indication of potential damage. Results from the computations show the same qualitative behavior as that observed in experiments: a re-entrant jet forms in the direction of propagation of the pulse and penetrates the bubble during collapse, ultimately hitting the distal side and generating a water-hammer shock. As a result of the propagation of this wave, wall pressures on the order of 1 GPa may be achieved for bubbles collapsing close to the wall. The wall pressure decreases with initial stand-off distance and pulse width and increases with pulse amplitude. For the stand-off distances considered in the present work, the wall pressure due to bubble collapse is larger than that due to the incoming shockwave; the region over which this holds may extend to ten initial radii. The present results indicate that shock-induced collapse is a mechanism with high potential for damage in shockwave lithotripsy.
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125, USA. johnsen@stanford.edu
authors.forename: Eric
authors.initials: E
authors.lastname: Johnsen
authors.forename: Tim
authors.initials: T
authors.lastname: Colonius
mesh_terms: D003198:Computer Simulation; D005740:Gases; D008096:Lithotripsy / Q000009:adverse effects / Q000295:instrumentation; D008962:Models, Theoretical; D009038:Motion; D009716:Numerical Analysis, Computer-Assisted; D011312:Pressure; D013499:Surface Properties; D013997:Time Factors
chemical_list: D005740:Gases