CFD Modeling of Droplet Flows in Microchannels in Slip Flow Regime

Abstract

Flow in microchannels is an important area of research in engineering because its importance in areas such as micro-machinery. In addition, hydrophobic materials have become increasingly attractive for use in fabrication of microfluidic devices. However, even when in macroscopic flows the non-slip boundary condition on solid wall has been well accepted, a number of recent studies have found evidences of slip velocities for liquid flow on hydrophobic surface. In this study, numerical simulations of two-phase flow of micro-droplet in a continuous base fluid in a 2D microchannel were performed using a commercial software package. Both slip and non-slip flows were considered. Continuous phase slip over wall channels was considered modeling all range of possible Knudsen numbers. Three drops of different sizes were modeled. Results were expressed in term of pressure drop and Reynolds numbers. Droplet interface deformation and velocity fields inside both droplets and continuous phase were determined. Results show that for Knudsen numbers between 0.01 and 0.1, Reynolds number increases in a proportion in the order of 20%. In addition pressure drop notably increase when large drops are considered.