Abstract
Flow-induced in-line oscillation of a circular cylinder has been experimentally studied by free oscillation tests in a water tunnel. The cantilevered cylinder models were supported elastically by a plate spring so as to oscillate only in the in-line direction. An end-plate (=3d) was fitted to the free end of the cantilevered cylinder to examine the influence f end-effects on the flow. Air-injection pipes were set at 300mm (=15d) upstream before a cylinder model to examine the influence of bubbles. The response characteristics of cylinder with aspect ratio of 10 in bubble flow shows only one excitation region at Vr=1.1 to 3.2 and the oscillating amplitude is smaller than that is uniform flow at Vr=2.0 to 3.2. While a cylinder with aspect ratio of 14 in bubble flow has two excitation regions. The amplitude in the second excitation region (2.5<Vr3.0) is smaller than that in uniform flow. The response characteristics of cylinder with an end-plate in bubble flow shows two excitation regions near half of the response velocity. The amplitude in second excitation region (at Vr=2.5 to 3.3) is smaller than that in uniform flow.
Published Version
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