Radical production inside an acoustically driven microbubble

Abstract

The chemical production of radicals inside acoustically driven bubbles is determined by the local temperature inside the bubbles and by their composition at collapse. By means of a previously validated ordinary differential equations (ODE) model [L. Stricker, A. Prosperetti, D. Lohse, Validation of an approximate model for the thermal behavior in acoustically driven bubbles, J. Acoust. Soc. Am. 130 (5) (2011) 3243-3251], based on boundary layer assumption for mass and heat transport, we study the influence of different parameters on the radical production. We perform different simulations by changing the driving frequency and pressure, the temperature of the surrounding liquid and the composition of the gas inside the bubbles. In agreement with the experimental conditions of new generation sonochemical reactors, where the bubbles undergo transient cavitation oscillations [D. F. Rivas, L. Stricker, A. Zijlstra, H. Gardeniers, D. Lohse, A. Prosperetti, Ultrasound artificially nucleated bubbles and their sonochemical radical production, Ultrason. Sonochem. 20 (1) (2013) 510-524], we mainly concentrate on the initial chemical transient and we suggest optimal working ranges for technological applications. The importance of the chemical composition at collapse is reflected in the model, including the role of entrapped water vapor. We in particular study the exothermal reactions taking place in H2 and O2 mixtures. At the exact stoichiometric mixture 2:1 the highest internal bubble temperatures are achieved.

Classification of the bifurcation structure of a periodically driven gas bubble

“…This phenomenon is known as the bubble collapse. The generated extreme conditions are exploited by many industrial applications including sonochemistry [5][6][7][8][9][10], food processing [11][12][13] or even medical treatment [14][15][16][17].…”

Nucleus factory on cavitation bubble for amyloid β fibril

“…Sharp temperature increases around 40 and 80 μ s in Fig. S8 (b ) correspond to the bubble-collapse events, at which temperature inside bubble reaches ~10,000 K; this is acceptable because it was experimentally shown that temperature inside bubble could reach near 10,000 K at bubble collapse 29 for a single-bubble case, and this ultrahigh temperature field has been used for various chemical reactions 15 16 17 .…”

“…Promotion of chemical reaction by ultrasonic wave has been studied in the field of sonochemistry, where cavitation bubbles generated by ultrasonic wave are deeply related to sonochemical reactions 10 11 12 . Sonochemical reaction is principally a decomposition reaction for organic substances 13 14 : Ultrasonic cavitation bubbles repeat growth and collapse, and significant temperature increase (up to thousands of kelvins) occurs at the collapse, which promotes the pyrolytic decomposition of the soluble substances near the hot spot and also produces free radical species from water that oxidize the substances 15 16 17 . Such a sonochemical reaction has been also used in the study of amyloid fibrils to fibrillate aggregates for obtaining the seeds 2 18 .…”

High-performance GPU computations in nonlinear dynamics: an efficient tool for new discoveries

“…The first test model is the periodically excited Keller-Miksis equation that is a second order ordinary differential equation describing the radial pulsation of a single spherical gas bubble placed in an infinite domain of liquid [38]. During the radial oscillation of the bubble, due to the external forcing, its contraction phase can be so rapid (collapse) that the temperature inside can reach thousands of degrees of Kelvin inducing chemical reactions [39][40][41]. Therefore, this model is extensively used in the field of sonochemistry [42][43][44][45][46][47][48][49][50][51] to estimate the collapse strength and the chemical yield of a single bubble.…”