振荡水柱波能利用型透空堤的水动力特性及消浪机理研究

Pile-supported breakwater is one kind of new “green” breakwaters applicable to deeper waters, while oscillating water column is one kind of wave energy converters of broad application scope and high reliability. In this project, we combine these two concepts and propose a breakwater equipped with wave energy converters, which can shelter marine development and utilization against wave-attacking and meanwhile can provide sustainable and clean energy. Oscillating water column can attenuate wave through energy extraction and vortex-shedding dissipation in the oscillating flow field. Most of the research on oscillating water column considered it as a wave energy converter alone and focused on its energy extraction, while only a little research studied its wave protection. At first of this project, we will experimentally examine the reciprocating flow characteristics of the orifices and porous materials which are used to simulate turbine in details. On this basis, we will study the hydrodynamic characteristics of breakwater by the potential theory analysis, study the wave dissipation characteristics by the wave-flume experiments, and study the oscillatory flow field characteristics by the particle image velocimetry technology, to analyze the wave dissipation mechanisms of breakwater in-depth. It is expected to propose a structure of good wave protection, high wave energy extraction, small wave loads and promising engineering application. The successful implementation of this project will help promote the engineering application of pile-supported breakwater and provide a significant contribution to the research of oscillating water column as a wave energy converter alone.

透空堤是一种可适用于较深水域的新型“绿色”防波堤，振荡水柱是一种适用范围广、可靠性高的波能装置。本项目结合两者概念，提出一种波能利用型防波堤，为海洋开发利用活动防御波浪侵袭的同时，提供可持续清洁能源。振荡水柱可以通过波能提取和振荡流场中的涡动耗散来消减波浪，但目前将振荡水柱单独作为波能装置的研究较多，主要关注其波能提取，对其防浪效果涉及较少。本项目拟先对用来模拟涡轮机的孔口、多孔材料的往复流动特性进行详细试验研究。在此基础上，通过势流理论分析防波堤的水动力特性，通过波浪水槽试验研究防波堤的消浪特性，通过粒子图像测速(PIV)技术研究防波堤的振荡流场特性，深入防波堤消浪机理，以期提出一种防浪效果优良、波能提取较高、受波浪荷载较小、具有工程应用前景的振荡水柱波能利用型透空堤结构型式。本项目的顺利开展将为透空堤的工程应用推广提供一种新思路，研究成果对振荡水柱单独作为波能装置也有相当的借鉴意义。

本项目主要研究内容包括振荡水柱波能利用型透空堤水动力特性的理论分析和物理模型试验。在物模试验中改变波浪频率、孔口几何特征、开孔率等参数，通过同步时变的水柱振荡和气室内压力信号，对孔口往复流动特性展开研究，采用二次损耗系数和收缩系数来描述孔口往复流动特性，并构建了其与孔口几何特征的关系，建立了其定量表达，可以通过设计孔口的各种参数，做到特定流动特性的实验室准确模拟；基于线性微幅波理论和特征函数匹配法，建立了振荡水柱波能利用型透空堤势流理论模型，对振荡水柱波能利用型透空堤的水动力特性展开了多参数影响水动力分析，研究了波浪散射特性及理论最大波能利用发生条件，重点考虑了空气可压缩性的影响，并针对宽频谱波况采取了一种实际易行的优化控制策略；结合势流理论分析结果，建立了振荡水柱波能利用型透空堤在实验室波浪水槽中的物理模型试验方法，在不同波浪条件、气室结构特征、能量俘获系统阻尼影响下，分析了振荡水柱波能利用型透空堤的波能俘获、涡动耗散以及波浪透反射，研究其随各种参量的变化规律；搭建了高时间解析度PIV系统，采用高通滤波方法对试验图像进行前处理，多步求解方法和多时间间距方法对流速进行求解，可以高质量、宽范围地测量振荡水柱波能利用型透空堤的振荡流场瞬时流速，研究了振荡流场特性以及流场中旋涡生成、输移及消散过程，并分析了不同波浪条件、能量俘获系统阻尼及水位对振荡流场特性的影响。