S0502-3-2 リング設置による円柱からの渦放出抑制 : 渦放出抑制のメカニズム([S0502-3]噴流,後流および剥離流れ現象の解明と制御(3))

概要

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Omnidirectional reductions in drag and fluctuating forces can be achieved for a circular cylinder subjected to cross-flow by attaching cylindrical rings along its span at an interval of several diameters. In this work, flow visualizations and PIV measurement were performed in order to explore the mechanism of the vortex shedding suppression. The mechanism is considered as follows: The corner vortices formed on the ring edges inflows to the side of the ring due to a pressure gradient. This promotes the flow turbulence on the side of the ring, and thus, the separated flow from the side of the ring reattaches on the rear of the ring at Re_d ≥ 20000. This shrinks the wake behind the ring markedly, which induces a pair of large transverse circulations behind the ring. This flow interferes the formation of two-dimensional spanwise vortices, and consequently suppresses the periodic vortex shedding.
2010-09-04