双圆柱形浮体波能装置双自由度响应及转换效率分析

大部分波能装置是通过载体的振动吸收波浪能,双圆柱形浮体是其中一类波能装置,研究双浮体波能装置的振动特性对于设计及提高波能装置整体转换效率具有重要的指导作用.本文把双浮体波能装置物理问题简化为具有黏性阻尼二自由度的受迫振动系统,采用线性波理论和特征函数展开匹配法求解了波浪引起的激励力、附加质量和阻尼系数,基于振荡浮体的双自由度运动方程推导了波能装置的响应和转换效率表达式,并给出了优化原则.数值分析表明阻尼优化曲线有一波峰部分同弹簧无关,峰值的大小和对应的频率只同工况有关;当弹簧存在时,优化曲线呈现双峰值,双峰值对应的频率宽度随弹性系数的增大而变窄;低频段峰值对应阻尼较小,相对响应较大,高频段优化峰值对应相当大的阻尼,相对响应较小,几乎小于入射波波幅.

Response and conversion efficiency of a wave energy device consisting of double cylindrical floats with two degrees of freedom

Double cylindrical floats have been proposed as a device for extracting energy from waves by the carrier oscillating. The study on the oscillating property of the device can help to design the device and improve the conversion efficiency of the device. This paper simplifies the physics model of the two-body system as two degrees of freedom forced vibration system which has viscous damper. Based on the linear wave theory, wave excitation forces, added masses and damping coefficients can be derived by using the method of matched eigenfuntion expansions. The expressions of conversion efficiency and response of the device can be deduced from the equations of the carriers which have two degrees of freedom. The optimal principle is put forward on this basis. Numerical calculations indicate that damping optimal curve has a wave peak that is independent of the spring, and the value of the peak and the corresponding frequency are only related to the working conditions. Optimal curve presents two peaks when the spring exists, the corresponding frequency width between them becomes narrow while the elastic coefficient increases The damping is small at low frequency, but the response is relative high. The damping is relative high at the corresponding optimal peak frequency, but the response is relative small and nearly smaller than the amplitude of the incident wave.