The Alderney Race, located northwest of the Cotentin Peninsula (France), is a site with high tidal-stream energy potential. Circulation through the Alderney Race is complex, with current speed exceeding 3 m s−1 at neap tide. Towed acoustic Doppler current profiler (ADCP) measurements and static point velocity measurements were performed in July 2018 focusing on assessment of circulation and vertical structure of tidal currents. Transect surveys revealed peculiar features of local dynamics such as change in location of the tidal jet on ebb and flood flow. The spatial expanse of the tidal jet was quantified and regions with largely sheared or nearly homogeneous velocity distributions were identified on the cross-sections. Velocity profiles acquired along the cross-sections were accurately characterized using a power law. The spatial variability of the power-law exponent α was found to be large and correlated with the tidal conditions. The largest variation in profile shape was observed in the northern sector and assumed to be generated by the current interaction with a bathymetric constriction. The velocity profiles were found to vary from highly sheared on flood flow to nearly homogeneous on ebb flow, with corresponding range of power-law exponent α variation from 6 to 14. In the southern sector, over a relatively smooth bathymetry, the velocity profile shape was accurately approximated using the 1/7 power law with a range of variation of α from 6.5 to 8, with respect to the tidal conditions. To our knowledge, this is the largest field survey done using towed ADCP and the results could represent a significant advance in tidal site characterization and provide advanced information to turbine developers. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race'.

中文翻译：

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Alderney Race 中的进行中速度测量：朝向潮汐运动的三维表示

奥尔德尼赛马场位于科唐坦半岛（法国）西北部，是一个具有高潮汐能潜力的地点。Alderney Race 的环流很复杂，小潮时水流速度超过 3 m s−1。拖曳声学多普勒海流剖面仪 (ADCP) 测量和静态点速度测量于 2018 年 7 月进行，重点是评估潮汐流的环流和垂直结构。横断面调查揭示了局部动力学的特殊特征，例如潮汐射流在潮起潮落时的位置变化。潮汐射流的空间范围被量化，并在横截面上确定了具有大量剪切或几乎均匀的速度分布的区域。沿横截面获取的速度剖面使用幂律进行准确表征。发现幂律指数 α 的空间变异性很大并且与潮汐条件相关。在北部地区观察到轮廓形状的最大变化，并假设是由当前与测深收缩的相互作用产生的。发现速度剖面从洪水流上的高度剪切变化到退潮时几乎均匀的变化，相应的幂律指数 α 变化范围从 6 到 14。在南部地区，在相对平滑的水深测量上，速度剖面形状使用 1/7 幂律精确近似，α 的变化范围从 6.5 到 8，相对于潮汐条件。据我们所知，这是使用拖曳式 ADCP 进行的最大规模的现场调查，其结果可能代表潮汐场地特征的重大进步，并为涡轮机开发商提供先进的信息。本文是主题问题“奥尔德尼岛竞赛中潮汐动力学和潮汐能收集的新见解”的一部分。