The problem of aggregation of two spherical particles subjected to an acoustic field is numerically examined in this paper for the Oseen regime. The study focuses on the hydrodynamic mechanism known as the acoustic wake effect (AWE), and its influence on the acoustic agglomeration processes. Two nearby spherical particles are considered, subjected to acoustic fields under Oseen flow conditions and characterized by Reynolds numbers smaller than unity. The main goal of this work is to spawn the range of applicability of a theoretical analysis carried out previously by the authors, which was not applicable in a strict sense at distances shorter than 3.5 times the particle diameter. At these short distances the acoustic wake effect becomes the most intense and that is why it is interesting. A system of differential equations describing the particle dynamics is numerically solved. Particle trajectories are simulated during the complete approach process up to collision without any spatial restrictions, as well as the particles’ convergence velocity. A bidimensional description of the acoustic wake effect is performed in this numerical simulation. It reveals strong attraction between two interacting particles with their center-line oriented at angles from 0 º to 45 º with respect to the wave propagation direction. The results of this study are compared to those of the previous theoretical analysis. A good agreement between the two studies is found that evidences the applicability of the numerical treatment of the problem.

This study was supported by the research projects CYCIT, TAP-93-0230 and AMB- 96.1211-CO2-01 from the Spanish Ministery of Education and Science.

7 páginas, 7 figuras

Peer reviewed