Wavetank Characterisation Dataset 1 - 0.25Hz

This experiment is designed to derive the performance characteristics of a small wavetank used to test the efficiency of working scale models of wave power devices and compare these against the characteristics predicted by the theory used in its design especially at its theoretical optimal operating frequency of 1 Hz. The activity also aims to show whether waves in the tank show the characteristics of deep water waves as opposed to shallow water waves. In this case shallow water is defined as the case where wave amplitude is a significant proportion of overall water depth. In shallow water the wavelength can be expected to decrease as a function of decreasing water depth. The rig consists of a 4.9 metre tank with a paddle mechanism designed to generate continuous propagating waves. The tank features an angled beach which may be overtopped by generated waves to minimise reflections at the end of the tank. Water in the tank is constantly recirculated via a pump with water depth set by a combination of beach angle and pump flow rate. The physical and electrical characteristics of the tank are covered in more depth in Dataset 5. Datasets 1-4 represent a comparison between the observed and theoretical wavelengths of waves generated at 4 different paddle frequencies 0.25Hz, 0.4Hz, 0.7Hz and 1.0Hz for a fixed paddle stroke length. The experiments were conducted with the tank set for a nominal water depth of 500mm with 2 depth measurement probes set at a distance of 1.6 metres from each other. Results suggest that the waveforms were not good quality for any of the tested frequencies but that the observed wavelength better approximates predicted wavelength as the frequency is increased with good results at 1Hz. It can be concluded that the tank should be used at a frequency of greater than 1 Hz with the caveat that available wave power decreases as frequency increases. At 1 Hz the generated waves exhibit the characteristics usually seen at intermediate depth.

本实验旨在获取用于测试波浪发电装置缩尺模型工作效率的小型造波水池的性能特性，并将其与设计阶段采用的理论预测特性进行对比，尤其在其理论最优工作频率1赫兹（Hz）的工况下。本实验同时旨在验证水池内生成的波浪是否具备深水波浪特性，而非浅水波浪特性。此处对浅水的定义为：波幅占总水深比例可观的工况，在浅水环境中，波长会随水深减小而呈缩短趋势。该实验装置为长4.9米的造波水池，配备用于生成连续传播波浪的桨叶式造波机构。水池末端设有斜向消波滩，可通过造波产生的波浪越顶来最大限度降低水池端部的反射波。水池内水体通过水泵实现持续循环，水深由消波滩角度与水泵流量共同调控。该水池的物理与电气特性详见数据集5。数据集1至4对比了固定桨叶冲程长度下，以0.25Hz、0.4Hz、0.7Hz及1.0Hz四种不同桨叶频率生成的波浪的实测波长与理论波长。本次实验中，水池设定标称水深500mm，并布置了两个间距1.6米的水深测量探头。实验结果表明，所有测试频率下的波形质量均欠佳，但随着频率升高，实测波长与理论预测值的吻合度逐步提升，在1Hz工况下取得了良好的匹配效果。由此可得出结论：该水池应在高于1Hz的频率下运行，但需附带约束条件：可用波浪功率会随频率升高而降低。在1Hz工况下，生成的波浪呈现出通常见于中等水深环境中的波浪特性。