Longitudinal vortex structure in the flow field produced by a vortex ring impinging on a flat plate

The flow field produced by a vortex ring at Re = 2600 impinging on a flat p late was examined in detail using the smoke visualization method. The longi tudinal Vortex structure with a finger-like configuration was found which p lays a crucial role in forming azimuthal coherent structures with a cross s ection that resembles that of an orange; the structures promote the flow fi eld into turbulent state. The generating and developing process of the long itudinal vortex are discussed, and the topological aspects are inferred by integrating the information obtained through various local visualizations. (C) 2001 The Japan Society of Fluid Mechanics and Elsevier Science B.V. All rights reserved.