Dispersion at low and high peclet numbers in finite-length patterned microchannels

Abstract

The present work focuses on laminar dispersion of solutes in finite-length patterned microtubes. Dispersion is strongly influenced by axial flow variations caused by patterns of periodic pillars and gaps in the flow direction. We focus on the Cassie Baxter state where the gaps are filled with with air pockets and thus free-slip boundary conditions apply at the liquid-air interface. The analysis of dispersion in a finite-length microtube is approached by considering the temporal moments of solute concentration. With this approach it is possible to investigate the dispersion properties at low and high Peclet numbers and therefore how the patterned structure of the microtube influences both the Taylor-Aris and Convection-dominated dispersion regimes. Numerical results for the velocity field and for the moment hierarchy are obtained by means of Finite Element Method (Comsol 3.5).