Interaction Between a Vortex Ring and a Uniform Cross-Flow

This paper describes features in the structure of a laminar vortex ring ejected vertically from an elevated pipe into a uniform horizontal cross flow. Measurements are obtained by particleimage velocimetry (PIV) and flow-visualisation images are obtained by planar-laser-induced fluorescence (PLIF). Cross flow produces a shear layer over the open end of the elevated pipe. As a vortex ring is ejected, it lifts the cross-flow shear layer away from the elevated pipe. As the sides of the shear layer stretch and convect in the direction of the cross flow, they form a pair of counter-rotating “columnar” vortices. The columnar vortices link the rear of the pipe to the middle of the vortex ring.