| Summary: | 碩士 === 逢甲大學 === 水利工程與資源保育研究所 === 96 === This study set up a numerical simulation that used to discuss mechanism of the lift for a transversely oscillating cylinder. The Navier-Stokes equation is solved by a primitive method for the flow field. Then, a spectrum analysis is used to analyze the time series of the lift force to obtain the frequency and the energy of the shed vortices. The transverse vibration of the cylinder will affect vortex shedding when fluid flows over the cylinder. The vortices of vibrating cylinder will cause different lift and drag from those of fixed cylinder. This article uses three type of figure, i.e. streamline figure, pressure figure, and vorticity figure, to study the observation methods and characteristics of vortex. Then uses pressure figure and wall pressure figure to analyze the effect of cylinder vibration to the lift. Finally comprehensively discusses the mechanism of cylinder vibrating frequency to the lift. The results showed that pressure figure is the best for the observation of vortices. In the lock-on region, higher cylinder vibrating frequency gave greater vortex energy, more distorted wall pressure distribution , and larger lift. In the buffer region, vortice were weakened with less energy, and less distortion of the wall pressure, and finally caused lower lift.
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