Lateral Migration and Focusing of Inerial Particles in Two-Phase Flows of Boundary-Layer Type

Abstract The lifting force exerted on particles in shear flows can significantly affect the admixture distribution in near-wall gas/liquid-particle/droplet flows. For small particle Reynolds numbers based on the relative velocity, shear rate, and particle angular velocity, the expression for the lifting force was first obtained by P. Saffman in 1965 and corrected in 1968. In this study, we use a modified (extended to finite Reynolds numbers) expression for the lifting force proposed by R. Mei in 1992. In the framework of the one-way coupled two-fluid model we consider three examples of laminar gas/liquid-particle flows of boundary layer type with inertial inclusions: the two-phase Blasius problem on a horizontal and a vertical plate, gas-particle flow in a near-wall dusty plane jet, and inertial-particle focusing in an axisymmetric profiled microchannel. In all examples considered the lifting force exerted on the particles plays a crucial role and results in lateral migration and focusing of the dispersed admixture. The calculations of the particle concentration in the Blasius problem are compared with available experimental data. The study is based on the two-phase boundary layer approximation and the Full Lagrangian approach (FLA), proposed in previous publications of the authors. This approach makes it possible to calculate all particle parameters, including the number density, from the solution of systems of ordinary differential equations on chosen particle trajectories. The flow structure in the regions of crossing particle trajectories and the locations of caustics can also be studied by this method. The results obtained may be of interest for the development of technologies which use near-wall dilute two-phase flows and focused particle beams.