PNNL

Abstract

Typically, bump array devices separate submicron particles where gravitational effects remain small. However, as particle size increases from a few microns to hundreds of microns, gravitational effects become important and settling may induce vortex formation. This article shows under laminar flow that these vortices suffice to disrupt flow fields, frustrating particle separation. The size cutoff, below which vortices do not form, is determined and the dependence of the cutoff on viscosity, particle properties and separator orientation is quantified.