Drag Coefficient Correction for Spherical and Nonspherical Particles Suspended in Square Microducts

Even though drag in creeping flow has been extensively studied in the past, recent developments in microfluidic technologies have led to a reevaluation of the drag equations that were theoretically derived for ideal cases. Stokes’ Law is the bulwark of equations describing drag in creeping flow, but it applies in cases of uniform flow around a spherical object. Empirical and theoretical corrections to the Stokes drag for other particle shapes have been proposed, as well as corrections that account for the presence of walls that affect the shape of the velocity profile around the particle. The present work utilizes computational fluid dynamics to investigate the validity and the differences between results obtained with these equations at low Reynolds number flows. In addition, simpler equations using the ratio of the diameter of the particle to the height of the channel and the aspect ratio of nonspherical particles are used to predict drag for particles that are spherical, ellipsoidal, and cylindrical in square microducts.