Measurable metrics for characterisation of large-scale turbulent structures in tidal races for the marine tidal energy industry

随着气候变化要求英国向低碳能源转型，海洋可再生能源产业对英国未来的能源安全至关重要。海洋能源是一种巨大的、尚未开发的资源，英国周围的浅海是全球最好的潮汐能资源之一，约占总资源的10%。因此，潮汐能产业是英国经济中一个新兴且稳步增长的部门。然而，潜在的最高产量潮汐环境（即潮汐竞赛）是特别具有挑战性的开发环境，因为强大的水流，特别是非常湍流的水流。因此，潮汐能转换器（TECs）的最佳和有效设计需要对潜在开发地点的流动和湍流进行表征。该项目的目的是发展技术，直接应用于提高海洋测量设备的技术能力，以表征湍流的关键方面，从而确定适当的湍流参数，以协助tec的设计和操作。发展海洋潮汐能部门的主要技术挑战是设计、部署和长期操作具有成本效益的流内TEC设备，这些设备能够在潜在高产量地区（即潮汐能地区）的极端条件下生存。迅速的潮汐流)。因此，该行业发展的一个关键要求是现场调查的方法，该方法可以提供适当湍流参数的特征。测量表明，湍流动能耗散与潮流速度密切相关，在狭窄的通道中，它是高度可变的，对于给定的流速波动超过一个数量级。然而，常用的声学技术不能解决这种耗散的可变性，这是由相干结构的形成造成的。此外，这些测量并不能提供更大尺度湍流结构的信息。规模，结构/一致性和应力，这是最有可能损害潮汐能基础设施的结构完整性和影响发电量。在这里，我们建议开发和测试新的方法，使用最新一代现成的5波束声学多普勒电流分析器（ADCPs）的测量结果，在与潮汐能发电基础设施设计直接相关的长度尺度上提供更合适和全面的湍流特征。通过与我们的合作伙伴，ADCP制造商Nortek和海洋能源现场调查公司Partrac的合作，这些发展的直接相关性将得到保证。特别是，我们将利用我们以前的观察，即应用于多波束声学电流剖面仪的结构函数技术可以用来提供湍流各向异性的测量。

The marine renewable energy industry is vital to the future energy security of the UK as climate change necessitates the shift towards low carbon energy sources. Ocean energy represents a vast and largely untapped resource and the shallow seas around the UK represent one the best tidal energy resources globally, accounting for some 10% of the total resource. In consequence, the tidal energy industry is an emerging and steadily growing sector of the UK economy. However, the potentially highest yield tidal environments (i.e. tidal races) are particularly challenging environments for development due to the strong currents and in particular very turbulent flows. Optimum and efficient design of tidal energy convertors (TECs) therefore requires the characterisation of both the flow and turbulence at potential sites for development.The aim of this project is to develop techniques, which are directly applied to enhance the technological capability of oceanographic measurement equipment, for the characterisation of key aspects of turbulence, and hence identification of appropriate turbulence parameters, to aid the design and operation of TECs. The main technical challenge in the development of the marine tidal energy sector is the design, deployment and operation, over the long term, of cost effective in-stream TEC devices which are able to survive the extreme conditions associated with potentially high yield regions (ie. rapid tidal currents). A key requirement in the development of the industry is therefore methodology for site survey which provides characterisation of appropriate turbulent parameters. Measurements demonstrate that turbulent kinetic energy dissipation is strongly linked to tidal current speed, in a confined channel it is highly variable, fluctuating by over an order of magnitude for a given flow speed. However, commonly used acoustic techniques fail to resolve this variability in dissipation, which results from the formation of coherent structures. Furthermore, these measurements do not provide accessible information on the larger scale structure of turbulence, ie. the scales, structure/coherency and stress, which are most likely to compromise the structural integrity of the tidal energy infrastructure and effect power yield. Here we propose to develop and test new methodologies, using measurements from the latest generation of off-the-shelf 5-beam acoustic Doppler current profilers (ADCPs), to provide a more appropriate and comprehensive characterisation of turbulence at length scales directly relevant to the design of tidal stream energy generation infrastructure. The immediate relevance of these developments will be insured through collaboration with our partners, ADCP manufacturer Nortek and marine energy site survey company Partrac. In particular, we will exploit our previous observations that structure function techniques applied to multi-beamed acoustic current profilers can be used to provide a measure of anisotropy of turbulence.