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LONG-WAVELENGTH VORTEX MOTION INDUCED BY FREE-STREAM TURBULENCE

Sean C.C. Bailey
Advanced Fluid Mechanics Research Group Faculty of Engineering Science, UWO London, Ontario, N6A 5B9, Canada; Department of Mechanical Engineering University of Kentucky Lexington, KY 40506, USA

Bahareh Estejab
Department of Mechanical Engineering, University of Kentucky Lexington, KY, 40506, USA

M. Robert
Department of Mechanical Engineering University of Ottawa Ottawa, ON, K1N 6N5, Canada

Stavros Tavoularis
Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario KIN 6N5, Canada

Аннотация

This study further examines experimentally the motion of an isolated vortex immersed in grid-generated free-stream turbulence. Using a novel analytical procedure, we determined approximately the time history of the vortex axis position from velocity vectors at two locations measured simultaneously with the use of hot-wire anemometry. We identified a long-wavelength, organized, helical motion of the vortex axis, which is present in both low-turbulence and high-turbulence streams, thus pointing to a universal instability mechanism. Free-stream turbulence appears to intensify this instability, while simultaneously enhancing the stochastic motion of the vortex axis.