Dependence of acoustic trapping capability on the orientation and shape of particles

This paper presents an experimental and theoretical investigation of the dependence of acoustic trapping capability on the orientation and shape of particles to be trapped in different media. In the experimental investigation, two sharp edges of metal strips in ultrasonic vibration are used to trap particles in air. Experimental particles are made of clay, having the same mass and volume but different shapes. In the theoretical investigation, a method which combines the analysis of finite element method and theory of acoustic radiation force is used to calculate the acoustic radiation force acting on particles with different shapes and orientations. Both the experimental and theoretical results show that the acoustic trapping capability depends on the orientation and shape of particles. It is found that both in air and in water, for a particle with a given shape, the trapping capability is different at different orientations; for some commonly shaped particles, such as rectangular cuboid, cylinder, cone, cube, sphere, and hollow cylinder; the trapping capability for each particle shape at its best trapping orientation decreases in the listed sequence of shapes.