On Dominant Oscillation Frequency of a Simplified Fluidic Oscillator

概要

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In the present study, we investigate a self-excited oscillatory phenomenon of a two-dimensional confined jet with a rectangular-cross-section cylinder as a downstream target. More specifically, in order to reveal the effects of a kinematic parameter the Reynolds number Re and various geometric parameters upon the jet-oscillation frequency fD, we conduct experiments at Re < 5000 in water and in air by an ultrasonic velocity profiler and a hot-wire anemometer, respectively. As a result, we specify the effects of Re and four non-dimensional geometric parameters upon fD, which is non-dimensionalised as the Strouhal number St. As the four geometric parameters, we consider (1) the streamwise target size, (2) the channel breath, (3) the cross-streamwise target size and (4) the target distance in non-dimensional forms with a length scale of the jets breadth. It is found that the Re effect is negligible. This guarantees a wide-range workability as flowmeters. All the results can be summarised in an empirical formula describing the relation of St with the four geometric parameters.