Hydrodynamic swirl decay in microtubes with interfacial slip

Abstract

The decay of swirl in a laminar swirling flow of liquid through a microtube is numerically investigated. The Navier-Stokes equations are solved with velocity slip at the wall. The influences of swirl–slip interactions on swirl decay are investigated. The decay of swirl is quantified by the variation in the ratio of swirl number at a section with that at the inlet (S/S₀) along the flow. A mathematical expression of S/S₀ with nondimensional distance along the flow from the inlet is developed in terms of the pertinent flow parameters like Reynolds number, inlet swirl number, dimensionless slip length, and dimensionless critical radius of inlet Rankine vortex profile for the swirl. Such a functional relationship may act as an elegant design tool for microtubes characterized with swirling flows in presence of interfacial slip.