质量比和阻尼比对高阻尼涡激振动的影响

涡激振动水生能源是一种可在低流速条件下利用水中涡激振动现象从周围流场中提取水流动能的新兴可再生清洁能源技术,其能量转换装置在进行能量传递和转换过程中会对涡激振动系统引入较高的阻尼,使其不同于以往研究较多的低阻尼涡激振动系统。文章建立了一个单自由度涡激振动模型,模型采用受迫振动实验得到的流体力数据,通过迭代求解涡激振动能量转换装置的动力响应,进而计算系统转换功率。通过对质量比m*和阻尼比ζ等重要参数对涡激振动响应及能量转换效率影响的细致研究,揭示出:频率锁定的发生及较大能量转换效率的无量纲流速范围主要受质量比控制;最大能量转换效率主要受质量—阻尼参数m*ζ控制,并且存在一个最优值;出现最大能量转换效率的无量纲流速与m*ζ有关,在m*ζ0.2的范围内出现最大能量转换效率的无量纲流速随质量比和阻尼比的变化而变化,而在0.2m*ζ0.7的范围内与阻尼比无关,主要取决于质量比。

Effects of mass and damping ratios on VIV of a circular cylinder under high damping conditions

The vortex induced vibration (VIV) based hydrokinetic energy converter discussed in this paper is a new concept in power generation from fluid flows in oceans,rivers and streams,aiming to harness aquat-ic energy from slow moving water currents.The transmissions and conversion of energy will induce high me-chanical damping back to the VIV system, and this makes it different from the low damping VIV system which was concerned in many previous studies.A mathematical model of a circular undergoing VIV is pre-sented using the experimental data from forced vibration tests for predicting the dynamic response and ul-timately determining the power that can be extracted.The effects of the mass ratio m*and the damping ra-tio ζ on the VIV response and the energy conversion efficiency are investigated.The analysis reveals that:(1)The dimensionless velocity where the onset of the lock-in occurs and the range of dimensionless veloc-ities with significant efficiency is mainly governed by mass ratio; (2) The maximum efficiency is principally influenced by the mass-damping parameter m*ζ;(3)For m*ζ<0.2,the dimensionless velocity where the max-imum efficiency appearance depends on the mass ratio and the damping ratio, but for 0.2