Motion of submicron particles in a supersonic laminar boundary layer under hypergravity

The process of submicron particle movement in laminar boundary layers has many applicable backgrounds including high-speed centrifugal devices. Although a big progress has been made on this problem during the last decades, many mechanisms in this process still remain unclear. Here, we developed a theoretical model to understand how submicron particles will behave when they are in a supersonic laminar boundary layer above an adiabatic plate along with the main stream under both zero gravity and hypergravity. In this model, we applied the Lagrangian method to track the particles and calculate their trajectories, and the Eulerian method was used to calculate the flow field. Because of the large velocity and temperature gradient near the wall and the small size of the particle in this question, and the high gravity field, five forces (e.g., drag force, Saffman lift force, thermophoretic force, Brownian force and gravitational force) acting on the particle are considered, and the role of each force is studied. The effects of entering position, intensity of gravity field, the size and density of particles are investigated. As a result, we discovered that there are three particle movement patterns when they enter the supersonic boundary layer under regular gravity and other patterns under high gravity. This research gives a better understanding of the particle movement process in the supersonic laminar boundary layer, which can be a useful instruction for the industrial processes relating to this phenomenon. Crown Copyright (C) 2015 The Authors. Published by Elsevier Ltd.