ノズル内の二次元物体後流によってフラッピングする二次元噴流の渦構造 : 第2報,可視化観測および時系列画像相関解析(流体工学,流体機械)

概要

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When a plane jet exhibits flapping motion, two distinctive peaks, f_1 and f_2, appear in the spectrum of fluctuating velocity. The mean frequency is half of the frequency, f_v, of vortices shedding from a two-dimensional body that is installed in a jet nozzle contraction. Jet mixing has been enhanced by the flapping motion with a low frequency, f_3=f_1-f_2, which is considered to be caused by an inharmonic excitation. Vortical structures in the flapping jet are investigated by using flow visualization, image correlation and laser Doppler velocimetry. Vortices are seen to roll up asymmetrically at the jet nozzle exit, at a double frequency of that of the vortex shedding from the cylinder. Two types of vortices are formed by coalescence between these vortices and the vortices shedding from the cylinder. The periodicities of these two types of vortices are found to be equal. It is noted that vortices with f_1 or f_2 do not exist in the flow. The f_1 and f_2 are caused by the modulation of amplitude of the coalesced vortical structures with half of the flapping frequency, f_3.
一般社団法人日本機械学会の論文
2006-07-25