Aerodynamic focusing in a channel with oscillating walls

We investigate analytically and numerically aerodynamic focusing of aerosol particles in the incompressible Poiseuille flow in a two-dimensional channel where the channel walls perform small oscillations perpendicular to the channel axis. The fluid–particle interaction is described by a linear drag force. Focusing efficiency is investigated for variety of flow and particle parameters, expressed in terms of dimensionless groups, namely parameter ε, characterizing the amplitude of wall oscillations; flow velocity parameter where U is the maximal velocity of the imposed flow, h is the channel half-height, ω is the angular frequency of oscillations; and frequency parameter ωτ, where τ is Stokes relaxation time. It is shown that wall channel oscillations with frequency of about 1 kHz can focus micron-size particles on axial distances comparable to several channel heights.