Acoustic concentration of particles in piezoelectric tubes: Theoretical modeling of the effect of cavity shape and symmetry breaking

Abstract

A new class of simple, highly efficient, cylindrical acoustic concentration devices has been developed based upon cylindrical (or near cylindrical) geometries [Kaduchak et al., Rev. Sci. Instrum. 73, 1332–1336 (2002)] for aerosol concentration applications. The concentrators are constructed from single PZT tubes driven at or near the breathing mode resonance. Acoustic concentration of aerosols is performed within the tube cavity. It has been found that slight modifications to the cylindrical cavity geometry can significantly increase the collection efficiency and assist in precise particle positioning. This paper analyzes the theoretical framework for the acoustic concentration of particles in these devices for various geometrical perturbations. The cavity geometries studied are (1) hollow cylindrical piezoelectric tube, (2) hollow piezoelectric tube with an inner concentric solid cylinder insert, (3) a hollow piezoelectric tube with a concentric elliptic insert which breaks the circular-cylindrical symmetry, and (4) a hollow elliptic cylindrical piezoelectric tube. It is shown that breaking the circular symmetry within the cavity localizes the particles in small spatial regions within the cavity. This localization of particles may be very useful in applications requiring aerosol collection or particle stream positioning.

Acoustofluidics 22: Multi-wavelength resonators, applications and considerations

“…These effects are not limited to water or even liquids; Kaduchak (Fig. 1f) 23 and Anderson 27 have both brought aerosols of 5 mm water droplets to the nodal planes.…”

“…(f) Water droplet aerosol driven to nodes. 23 Reproduced with permission of American Institute of Physics for the Acoustical Society of America.…”

“…where E is the elastic (Young's) modulus (70.8 GPa), r is the density 2700 kgm 23 , n is Poisson's ratio (0.3375) and f is the frequency. The wavelength depends on the phase velocity not the bulk velocity.…”

Scaling-up ultrasound standing wave enhanced sedimentation filters

“…3c and e). Although this appears to indicate that nodal planes are stacked along the axis of initial sound propagation, our explanation for the node alignment is that the clamping partially fixes one wall reducing its displacements and this allows duct breathing [48] but reduces flexing. Breathing transfers compression waves into the fluid, parallel to the fixed wall.…”

Focusing in a quadrupole acoustic channel

“…This would lead to particle concentrating along these lines. Kogan, Kaduchak, and Sinha (2004) and Marston and Thiessen (2004) have shown that the use of non-cylindrical tube shape and symmetry breaking allow particle focusing along only one line. Another issue is that high frequency ultrasound waves used by Goddard et al being applied to particle focusing in gas-filled tube result in strong sound attenuation and dissipation (Krasilnikov & Krylov, 1984).…”