Breakdown of Swirling Cavity Flow in a Diverging Circular Pipe

Abstract

There is often found a vortex breakdown as an abrupt velocity and structure change at some position along an axis of a swirling flow. To make clear the hydrodynamical characteristics of the breakdown of a swirling cavity flow in a diverging circular duct, experimental observations and hydrodynamic examinations of the breakdown have been made about the behavior of the cavity and velocity or pressure distributions of water on the outside of the cavity. The experimental investigations for various swirling cavity flows revealed quantitatively large velocity changes at downstream of breakdown and close relationships between the shape of the cavity and the states of liquid swirling motions. The effect of the varying duct area on the abovementioned relationships also examined by comparison of the results in the diverging circular duct with those in the straight circular duct.