ON THE DRIFT OF AEROSOL-PARTICLES IN SONIC FIELDS

The drifting motion of aerosol particles enclosed in vessels subject to ultrasonic oscillations is analysed theoretically. The geometry considered here is of vessels with dimensions not exceeding the ultrasonic wavelength. This geometry is quite different from previously treated cases, where the flow field dimensions measured many times the ultrasonic wavelength and where the aerosol particles were found to move towards nodes and towards loci of maximum amplitudes, according to their sizes. The results obtained here are rather different and indicate that all particles move away from the oscillating wall and towards the stationary one. These results conform to the motivation of the investigation, which is to protect a clean site from settling particles. The analysis incorporates two-scale expansions methods applied to the multiphase flow equations for a one-dimensional flow model. The results are constructed by the superposition of a slow mean motion of the gas and a fast oscillatory motion associated with the eigenfunctions of the standing waves solution. The combined effect on the particles is a drift in the direction of the stationary wall.