Acoustic streaming of a sharp edge.

Anomalous acoustic streaming is observed emanating from sharp edges of solid bodies that are vibrating in fluids. The streaming velocities can be orders of magnitude higher than expected from the Rayleigh streaming at similar amplitudes of vibration. Acoustic velocity of fluid relative to a solid body diverges at a sharp edge, giving rise to a localized time-independent body force acting on the fluid. This force results in a formation of a localized jet. Two-dimensional numerical simulations are performed to predict acoustic streaming for low amplitude vibration using two methods: (1) Steady-state solution utilizing perturbation theory and (2) direct transient solution of the Navier-Stokes equations. Both analyses agree with each other and correctly predict the streaming of a sharp-edged vibrating blade measured experimentally. The origin of the streaming can be attributed to the centrifugal force of the acoustic fluid flow around a sharp edge. The dependence of this acoustic streaming on frequency and velocity is examined using dimensional analysis. The dependence law is devised and confirmed by numerical simulations.

Experimental study of occlusion break surge volume in 3 different phacoemulsification systems.

PURPOSE: To evaluate surge volume after occlusion breaks in 3 different phacoemulsification systems. SETTING: Alcon Research LLC, Lake Forest, California. DESIGN: Experimental study. METHODS: A mechanical spring eye model was used to test the Centurion with Active Sentry, WhiteStar Signature Pro, and Stellaris PC. Raw oscilloscope data were converted to volumetric and pressure measurements. Fitted average surge traces were generated for each test condition and used to develop an interpolation algorithm to predict transient occlusion break surge events. Two-dimensional heat maps were generated. RESULTS: During occlusion break surge, the Centurion with Active Sentry had smaller aqueous volume losses than the WhiteStar or Stellaris PC. Maximum surge volumes within the mechanical spring eye model displacement limit were 74.7 µL, 157.5 µL, and 151.7 µL using Centurion with Active Sentry, WhiteStar, and Stellaris PC, respectively. In the aphakic state, heat maps showed that Centurion with Active Sentry had less than 20% aqueous volume loss across all vacuum limits and target intraocular pressure; WhiteStar and Stellaris PC systems had up to 35% and 50% aqueous volume losses, respectively, at the higher vacuum limits. In the phakic state, Centurion with Active Sentry had up to 30% aqueous volume loss and WhiteStar and Stellaris PC systems had up to 50% aqueous volume losses. In addition, predicted transient traces demonstrated that Centurion with Active Sentry had the lowest percentage simulated aqueous volume loss compared with WhiteStar or Stellaris PC. CONCLUSIONS: Centurion with Active Sentry had lower aqueous volume losses after occlusion break than WhiteStar and Stellaris PC systems at all surgical settings.