Flow visualization of steady streaming in oscillatory flow through a bifurcating tube

Abstract

A steady streaming displacement of fluid elements is observed to occur during oscillatory flow through a Y-shaped tube bifurcation model at Womersley and Reynolds numbers that can exist in the human bronchial tree. The cause of the displacement is the effect of the asymmetric geometry on the oscillating velocity vector field. The steady streaming displacement is greatest for fluid elements that experience the highest velocity through the bifurcation junction. The maximum displacement observed increases with Re and a up to a Re of about 100 and a of about 5, after which a levelling off and gradual decline occur. Photographs of low-Re and low-a: cxpcrimcnts show the effects of secondary components of the steady-streaming displacement field which contribute to a complex circulation.