Field Stereoscopic Particle Image Velocimetry (FSPIV) system for high-resolution in-situ studies of freshwater and marine ecosystems

现场立体粒子图像测速（FSPIV）将在自然水生环境中实现3分量高分辨率瞬时速度测量，测量场覆盖面积达1.0 m × 0.5 m，采样率高达200 Hz。除了记录流场之外，FSPIV还可以使用相同的硬件同时捕获采样区域内的生物群信息，例如水生植物的运动或游动的鱼类的轨迹。目前还没有与拟议的制度类似的国际制度；这将是世界上第一个这样的项目。该技术的关键概念已由阿伯丁的研究小组开发并成功测试（Cameron 2011; Cameron et al., 2013; Biggs et al. 2019）。新系统将在此经验的基础上进行组装，并将在便携性、操作条件的灵活性和关键性能特征（如视场、空间和时间分辨率以及测量精度）方面大大提高当前的能力。新的FSPIV系统将包括一个轻型潜水头单元，其中包含8个数码相机和轻型片状光学元件，通过30米长的脐带连接到一个控制站，该控制站由脉冲激光器、图像捕获和存储设备以及便携式发电机组成。控制站可以安装，例如，安装在河岸、海滩或船上。连接头单元和控制站的脐带将保护摄像机的电源和数据电缆，以及一束光纤电缆，将激光能量传输到测量区域。该头装置可用于多种配置，以最大限度地提高部署灵活性，例如在浅水河流中掠过水面，或完全淹没在较深的河流、河口或海洋环境中。现代sCMOS相机的高灵敏度允许使用相对低强度的光片，这对野生动物完全无害和非侵入性。所提出的FSPIV系统超越了传统现场测量技术的能力，因为瞬时测量区域覆盖了一个大的二维流动区域，同时保持了大约1毫米的空间分辨率，而更常用的技术具有相对粗糙的分辨率，并且仅限于一维（沿线）或单点测量。8台摄像机覆盖FSPIV测量域，对速度分量的冗余估计允许低噪声统计估计，其不确定性可与最佳实验室设备相媲美。FSPIV提供的额外能力对于淡水和沿海环境的“下一代”研究至关重要。例如，FSPIV系统将被用于研究湍流与水生植物之间的相互作用，或者在自然环境中游动的鱼周围的流场。这些研究本质上是跨学科的，是水生生态学、生物力学和环境流体力学等已建立领域的桥梁（如Nikora 2010）。借鉴国家管理小组和国际咨询小组集体经验的多学科办法与世界领先的最新技术相结合，应确保目前对自然环境的认识发生革命性的变化。比格斯，H.，尼科拉，V.，吉宾斯，C.，卡梅伦，S.等，2019。生态水力学学报，1-18。卡梅隆，南卡罗来纳州，2011年。水环境学报，5(4),247-262。Cameron， S., Nikora， V.等，2013。流体力学学报，32(2):344 - 344。尼克拉，V. 2010。水土保持学报，26(2),367-384。尼古拉，V.，卡梅隆，S.等人，2012。环境流体力学：纪念Gerhard H. Jirka教授卷，217-235。

Field stereoscopic particle image velocimetry (FSPIV) will enable 3-component high-resolution instantaneous velocity measurements in natural aquatic environments with measurement fields covering an area up to 1.0 m by 0.5 m and sampling rates up to 200 Hz. In addition to recording flow fields, FSPIV can simultaneously capture information on biota in the sampling region using the same hardware, for example, the motion of aquatic plants, or the trajectories of swimming fish. There are no international analogues to the proposed system; it will be a world-first of its kind. Key concepts of this technology have been developed and successfully tested by the research group in Aberdeen (Cameron 2011; Cameron et al., 2013; Biggs et al. 2019). The new system will be assembled based on this experience and will substantially enhance current capability in terms of portability, flexibility in operating conditions, and key performance characteristics such as field-of-view, spatial and time resolution, and measurement accuracy. The new FSPIV system will consist of a lightweight submersible head unit containing eight digital cameras and light-sheet-forming optical components connected by a 30m long umbilical to a control station consisting of a pulsed laser, image capture and storage device, and a portable electric generator. The control station may be mounted, for example, on a river bank, a beach, or in a boat. The umbilical connecting the head unit with the control station will protect the power and data cables for the cameras along with a bundle of fibre optic cables to deliver the laser energy to the measurement region. The head unit may be used in a number of configurations maximising deployment flexibility, e.g. skimming the water surface in shallow rivers or fully submersed in deeper rivers, estuaries or marine environments. The high sensitivity of modern sCMOS cameras allows a relatively low intensity light sheet to be used which is completely harmless and non-invasive to wildlife.The proposed FSPIV system surpasses the capabilities of conventional field measurement techniques in that the instantaneous measurement region covers a large 2-dimensional flow area while maintaining approximately 1 mm spatial resolution, whereas more commonly deployed techniques have comparatively coarser resolution and are limited to 1-D (along a line) or single point measurements. With eight cameras covering the FSPIV measurement domain, redundant estimates of velocity components allow low noise statistical estimates with uncertainties comparable to the best available laboratory devices. The additional capability provided by FSPIV is vital for 'next generation' research studies in freshwater and coastal environments. The FSPIV system will, for example, be used to study interactions between turbulence and aquatic plants or the flow fields around swimming fish in their natural environment. Such studies are inherently cross-disciplinary and bridge the established fields of aquatic ecology, biomechanics, and environmental fluid mechanics (e.g. Nikora 2010). The combination of a multi-disciplinary approach drawing on the collective experience of a national management group and international advisory panel with state-of-the-art world-leading technology should secure transformative changes in current understanding of the natural environment. Biggs, H., Nikora, V., Gibbins, C., Cameron, S. et al., 2019. Journal of Ecohydraulics, 1-18. Cameron, S., 2011. Journal of Hydro-Environment Research, 5(4), 247-262.Cameron, S., Nikora, V. et al., 2013. Journal of Fluid Mechanics, 732, 345-372.Nikora, V. 2010. River Research and Applications, 26, 367-384.Nikora, V., Cameron, S., et al., 2012. Environmental Fluid Mechanics: Memorial Volume in Honour of Prof. Gerhard H. Jirka, 217-235.