Boundary layer coupling of solid particles in water in an ultrasonic field

In an ultrasonic field the region around a solid particle experiences small, localised velocity, pressure, and thermal fluctuations that decay rapidly over short length scales. Herein, we investigate the overlap of the rapidly decaying fields between two silica particles in water in the case where the particles are aligned with each other in the direction of the applied field. We explore the velocity, pressure, temperature, and vorticity in the region of the particles. We discuss the coupled particle effects in ultrasonic waves as particles begin to agglomerate or become more concentrated. The analysis is conducted in the long wavelength regime for particles of diameter 500 nm and frequency 9.7 MHz.