多浮摆式采能装置水动力性能的时域计算及模型试验

该文基于三维时域势流理论,对一种多浮摆式波浪能采能装置的水动力性能进行了时域模拟,获得了单浮摆及双浮摆系统的运动响应、浮摆所受波浪力矩及角速度。根据模拟参数,对单浮摆和多浮摆系统的水动力特性进行了比较。在此基础上,根据几何相似、运动相似等相似准则,进行了单、双浮摆系统的水力模型试验,获得了两种装置的波浪能采集效率。数值模拟及水力模型试验的结果表明,单浮摆的纵摇响应小于双浮摆的情况,浮摆间的相互作用可以提高波浪能的采能效率。     

摆动叶片式波浪能发电装置的水动力性能分析

简述了摆动叶片式波浪能发电装置的结构和工作原理,结合波浪力学和浅水波理论对摆动叶片进行理论分析,推导出俘获效率公式。为了分析装置的性能,采用Fluent软件仿真的方法,分析了摆角和波高参数对装置的水动力学性能的影响,提出最佳摆角概念,并研究了最佳摆角与波高的关系。研究结果表明:装置的俘获效率随着摆角的增大先增大后减小;随着波高的增加,装置的俘获效率在增加,研究结果为后期装置的试验提供了理论依据。     

漂浮式波浪能发电装置的水动性能分析

针对海况对波浪发电装置的影响,本文创新性地设计了一种新型漂浮式波浪能发电装置并描述了其工作原理。以该装置为基础并对装置波浪能采集部分建立了仿真分析模型。基于AQWA水动性能计算机软件,计算了装置中漂浮浮体在不同吃水深度、不同尺寸大小的RAO值,以及波浪波向和波浪周期对装置整体的时域响应。发现浸水达到1.3~1.4 m、漂浮体直径在2.8 m时RAO值达到理想值,当波浪推进方向在25°、波浪周期为3 s时浮体整体振幅较大,对波浪能采集效率有较大提高。     

新型波浪能发电装置的运动学分析

以开发利用海洋中的波浪能为要求,本文设计了一种漂浮式波浪能采集装置的新型波浪能发电系统。描述了装置的工作原理。并采用UG软件仿真对装置进行了运动学分析,仿真计算了该装置不同速度输入函数和恶劣海况条件下的传动性能,对传动过程的传递效果进行验证。研究结果表明:实验装置附加各类常见速度函数工作状态正常。实用性能高,对海况条件有较好的适应性。仿真效果与理论计算有较好的一致性,对漂浮式波能发电装置理论研究具有指导意义。     

环形阵列波浪能装置水动力特性的数值研究

基于线性势流理论,建立了多向不规则波浪与围绕一立柱分布的环形阵列波浪能装置相互作用的计算模型。分析了有无立柱影响下方向分布集中度参数对环形阵列波浪能装置能量捕获特性的影响,研究了阵列中各浮子的水动力特性。计算结果表明,方向分布集中度参数对阵列波浪能装置俘获效率无影响,但是对波能俘获功率产生较大的影响;通过对比无立柱情形下的计算结果,立柱的存在使得阵列装置的捕能功率在低频区明显增加,并使迎浪侧浮子的共振频率发生改变。     

拱坝动力反应中的水动力影响分析

根据当今的水库抗震设计的规定,在对大坝进行设计时,大坝的混泥土动态弹性模量应该在静态弹性模量的基础上增加30％,但是对岩体的动态弹性并没有任何规定。根据最新的国内外对这方面的研究成果,大坝混泥土动态弹性的模量应该在原来静态弹性模量上增加30％的基础上再增加到50％,岩体动态模量则应该变成静态变形模量。文章针对混泥土弹性以及有限元非线性动接触模型,对拱坝动力反应进行了有效的研究,先对本次研究的研究背景进行了相关的介绍;再对拱坝动力反应的计算模型做了详细的说明,其中包括横缝动接触模型以及水库压力模型;最后对不同水库的动压力模型进行了有效的分析总结。     

黏性流场中鱼类胸鳍的水动力性能分析

针对刚性胸鳍建立了二自由度、三自由度的运动模型.在此基础上,通过对基于求解雷诺平均纳维-斯托克斯(RANS)方程的商用计算流体力学(CFD)软件FLUENT的二次开发,采用其先进的动网格技术以及强大的后处理系统,详细计算了刚性胸鳍在黏性流场中的水动力性能.数值计算结果与最近物理实验结果进行详细比较和讨论.通过研究发现摆动胸鳍产生的独特表面压力分布以及尾涡变化方式是其产生较高推进性能的内在原因.     

带附体的门桥水动力性能试验研究

为了改善门桥的水动力性能,增设了对近壁面流场进行流动控制的水翼.船模水池中的模型拖曳试验表明,尽管水翼会增加门桥的水阻力,但只要合理地设计水翼的翼型、攻角和安装位置,可以改善和提高门桥水动力性能.     

Numerical study of hydrodynamic behavior and conversion efficiency of a two-buoy wave energy converter

In this paper we propose a two-buoy wave energy converter composed of a heaving semi-submerged cylindrical buoy, a fixed submerged cylindrical buoy and a power take-off(PTO) system, and investigate the effect of the fixed submerged buoy on the hydrodynamics of the heaving semi-submerged buoy based on the three-dimensional potential theory. And the dynamic response of the semi-submerged buoy and the wave energy conversion efficiency of the converter are analyzed. The difference of the hydrodynamics and the wave energy conversion efficiency of a semi-submerged buoy converter with and without a fixed submerged buoy is discussed. It is revealed that the influence of the fixed submerged buoy on the exciting wave force, the added mass, the radiation damping coefficient and the wave energy conversion efficiency can be significant with a considerable variation, depending on the vertical distance between the heaving semi-submerged buoy and the fixed submerged buoy, the diameter ratio of the fixed submerged buoy to the heaving semi-submerged buoy and the water depth.     

Effect of the PTO damping force on the wave pressures on a 2-D wave energy converter

The information of the wave loads on a wave energy device in operational waves is required for designing an efficient wave energy system with high survivability. It is also required as a reference for numerical modeling. In this paper, a novel system, which integrates an oscillating wave energy converter with a pile-restrained floating breakwater, is experimentally investigated in a 2-D wave flume. The measurements of the wave pressure on the wet-surface of the device are made as the function of the power take-off(PTO) damping force. It is shown that the wave pressure is significantly affected by the PTO system, in particular, at the edges, and the wave pressure varies under different wave conditions. From the results, conclusions can be drawn on how the PTO damping force and wave conditions affect the loads on the device, which is of engineering concern for constructing safe and reliable devices.     

Time-domain hydrodynamic analysis of pontoon-plate floating breakwater

The hydrodynamic behaviors of a floating breakwater consisting of a rectangular pontoon and horizontal plates are studied theoretically. The fluid motion is idealized as two-dimensional linear potential flow. The motions of the floating breakwater are assumed to be two-dimensional in sway, heave, and roll. The solution to the fluid motion is derived by transforming the governing differential equation into the integral equation on the boundary in time domain with the Green’s function method. The motion equations of the floating breakwater are established and solved with the fourth-order Runge-Kutta method to obtain the displacement and velocity of the breakwater. The mooring forces are computed with the static method. The computational results of the wave transmission coefficient, the motion responses, and the mooring forces of the pontoon-plate floating breakwater are given. It is indicated that the relative width of the pontoon is an important factor influencing the wave transmission coefficient of the floating breakwater. The transmission coefficient decreases obviously as the relative width of the pontoon increases. The horizontal plates help to reduce the wave transmission over the floating breakwater. The motion responses and the mooring forces of the pontoon-plate floating breakwater are less than those of the pontoon floating breakwater. The mooring force at the offshore side is larger than that at the onshore side.     

Optimization of an annular wave energy converter in a wind-wave hybrid system

A hybrid system of a spar-type floating offshore wind turbine and a heaving annular wave energy converter(WEC)provides a promising solution for collocated ocean renewable energy exploitation.The performance of the hybrid system depends on the dimensions of the WEC.Here an optimization method is proposed to determine the outer radius and the draft of the WEC under the wave condition in a randomly chosen operational site.First,three candidate models are selected based on three operational conditions of energy harvest:(1)The natural frequency of the system is matched with the peak wave frequency in the target site(referred to as synchronized mode),where the wind turbine and the WEC nearly heave together in a near-resonance condition,(2)The natural frequency of the WEC is matched with the peak wave frequency(ring mode),(3)The maximum wave power is harnessed under the peak wave frequency(target mode).Then the candidate modes are evaluated to obtain an optimum.Results show that the extracted wave power under the above operational conditions has an upper bound that can hardly be surpassed by enlarging the dimensions of the WEC only.The optimal annual wave energy production is achieved in the synchronized mode because of the superior performance of WEC over a wide bandwidth of effective energy conversion.     

海流能转换器叶片翼型的失速和水动力特性的数值研究

海流能转换器叶片翼型的水动力学性能优劣是海流能开发利用的关键因素.该文基于浙江工业大学水力学实验室设计的海流能转换器叶片,利用商川CFD模拟软件FLUENT对其叶片翼型在来流攻角从-4°～20°情形下的水动力特性进行了相应的数值模拟计算,得到翼型周围流场的速度分布、压力分布、翼型的失速特性以及水动力特性与攻角α的关系,可供设计高效的海流能转换器叶片时参考.     

Numerical examination of wave power absorption by the Edinburgh Duck wave energy converter device

A two-dimensional computational fluid dynamics(CFD)numerical model is developed to study the power takeoff(PTO)efficiency of an Edinburgh duck wave energy conve...     

Evaluation and optimization of a hybrid wave energy converter using excited motion response in two degrees of freedom

As waves in China seas are not high,a wave energy converter consisting of a coaxial annular buoy and a cylindrical buoy that extracts wave energy using two generators through the relative heave motion between the buoys and the pitch motion of the cylinder could be a more efficient choice.A dynamic model considering constraints and assuming linear power take-off is established to evaluate the power performance of the device.The influences of two key factors,the diameter of the annular buoy and the power take-off stiffness of the pitching generator,and their couplings on the power performance are analyzed.The power of the pitching generator accounts for a major proportion of the total power.An increase in the annular buoy diameter increases the power of the heaving generator while greatly decreases the power of the pitching generator.An increase in the power take-off stiffness of the pitching generator greatly decreases its power while has little influence on the power of the heaving generator.These two factors also influence the peak period of the total power.Based on the findings and practical limitations,an optimization strategy is proposed.Further,the device is optimized based on a real wave environment in Shandong Province,China.