Shallow depth flow fields and low velocity magnitudes are often challenges for traditional velocity measuring instruments. As such, new techniques have been developed that provide more reliable velocity measurements under these circumstances. In the present study, the two-dimensional (2D) surface velocity field of shallow basins is assessed by means of Large-Scale Particle Image Velocimetry (LSPIV). The measurements are carried out at the water surface, which means that a laser light sheet is not needed. Depending on the time scales of the flow and the camera characteristics, it is even possible to work with a constant light source. An experimental application of this method is presented to analyze the effects of shallow basin geometry on flow characteristics in reservoirs where large coherent two-dimensional flow structures in the mixing layer dominate the flow characteristics. The flow and boundary conditions that give rise to asymmetric flow are presented. Asymmetric flow structures were observed starting from basin shape ratios that are less than or equal to 0.96. By decreasing the basin length and increasing the shape ratio to greater than 0.96, the flow structure generally tends towards a symmetric pattern.

中文翻译：

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不同几何形状浅盆地中的大规模 PIV 地表流量测量

浅层流场和低速度幅度通常是传统速度测量仪器的挑战。因此，已经开发了在这些情况下提供更可靠的速度测量的新技术。在本研究中，浅层盆地的二维 (2D) 表面速度场是通过大尺度粒子图像测速法 (LSPIV) 评估的。测量是在水面进行的，这意味着不需要激光片。根据流动的时间尺度和相机特性，甚至可以使用恒定光源工作。提出了该方法的实验应用，以分析浅盆地几何形状对储层中流动特性的影响，其中混合层中的大型连贯二维流动结构主导着流动特性。介绍了引起非对称流动的流动和边界条件。从小于或等于 0.96 的盆地形状比开始观察到不对称的流动结构。通过减小盆地长度并将形状比增加到大于 0.96，流动结构通常趋向于对称模式。