The Effects of Reynolds Number on Energy Harvesting from FIV by a Square Cylinder

雷诺数对于方柱流致振动能量收集系统的影响

¹ School of Marine Since and Technology, Northwestern Polytechnical University, Xi'an 710072, China
² Key Laboratory for Unmanned Underwater Vehicle, Northwestern Polytechnical University, Xi'an 710072, China
³ Ladhyx, Ecole Polytechnique, Paris, 91128, France

Received: 29 November 2019

Abstract

Under the action of incoming flow, the square cylinder can generate more intense vibration responses than the circular cylinder, which is beneficial for energy harvesting. Numerical simulations for FIV of the square-cylinder energy conversion system are carried out. URANS equations are used in conjunction with the shear stress transport k-ω turbulence model to predict the flow, and the equations for vibrations are solved by the Newmark-β algorithm. The present numerical method is validated against the published data with good consistency. The Reduced velocity U_r is varied from 1-20, with corresponding Reynolds numbers of 24 000-160 000. The numerical results indicate that the Reynolds number significantly affects the frequency response, amplitude response, vortex shedding mode, and energy conversion efficiency. The highest efficiency point locates at Re=88 000, with a value of 7.156%. When Re>120 000, the system transits from vortex-induced vibration into galloping, and its vibration responses as well as energy harvesting characteristics change sharply. Fully developed galloping motion occurs when Re>144 000.

摘要

在来流作用下，相较于圆柱，方形柱体会发生更为明显的振动响应，其具备良好的海洋能量收集特性。针对方柱流致振动能量收集系统展开数值模拟研究，结合SST k-ω湍流模型求解URANS方程来获得流场信息，并通过Newmark-β方法求解固体振动方程。计算方法与实验数据及其他仿真模拟结果进行了对比，取得了良好的一致性。文章所选取的雷诺数范围为24 000~160 000，相应折合速度为3 < U_r < 20。结果表明，雷诺数对方柱的频率响应、振幅响应、脱涡模式以及能量获取效率均有不可忽视的影响。当雷诺数为88 000时整个系统能量收集效率最高，为7.156%；在雷诺数大于120 000后，方柱由涡激振动转向驰振，其振动响应及能量收集特性发生大幅变化，在雷诺数超过144 000后方柱进入完全驰振状态。