Decaying, Swirling Flow in a Pipe: Axial Velocity Field Development With Reversed Axial Flow

Abstract

Streamwise development of the axial velocity field in a confined, decaying swirling flow is explored in the present study. A tangential injection mechanism produces swirling flow at the inlet of a constant diameter pipe. Particle image velocimetry is employed for axial velocity measurements. Representative axial velocity profiles are presented for axial locations of 3 to 67 pipe diameters. The axial velocity profiles are asymmetric relative to the pipe centerline and the asymmetries persist as the flow develops in the axial direction. The eccentricity of the swirling flow spatially oscillates as the flow develops in the axial direction. The spatial oscillations of the axial velocity suggest that a vortex breakdown may be located near the inlet of the pipe and the entire pipe is the wake region of the vortex breakdown. The centerline axial velocity is also used to document the axial development of the flow. A comprehensive view of the flow field is provided by considering theoretical explanations presented in the literature for decaying, swirling pipe flows and for vortex breakdown.