Evaluating the efficacy of particle image velocimetry to estimate surface flow velocity in vegetated rivers

水生植物在低地河流中普遍存在，它们对河流水力学具有主导影响。流动阻力（通过曼宁粗糙系数）已被证明会随大型植物的生长而季节性变化，在水柱中水生植物丰富的时期，曼宁n值往往会记录得更高（Naden等人，2006年）。河道内生长的大量水生植物增加了水流阻力，降低了水流速度，从而增加了水深，增加了洪水泛滥的机会。粒子图像测速（PIV）是一种用于测量宏观流体系统中速度场的成熟技术，这种基于图像的方法被认为是估算表面流速的合适方法（Sun等人，2010年）。然而，很少有人尝试使用PIV技术来估计植被覆盖严重的河流的表面流速。由于水生植物对河流水力学有重要影响，在有植被的河流中测量地表流速对于防洪和供水是十分必要的。本计画的目的是评估PIV技术在有植物覆盖的河川表面流速估测上的效能。将PIV结果与声学多普勒流速仪（ADV）（现场）测量的结果进行比较，ADV是最常用的流速测量仪器之一，以评估其准确性

Aquatic plants are prevalent in lowland rivers and they exert a dominant influence on river hydraulics. Flow resistance (via Manning's Roughness Coefficient) has been shown to change seasonally in response to macrophyte growth, were higher values for Manning's n tend to be recorded during periods when there is a greater abundance of aquatic plants in the water column (Naden et al 2006). The increase in flow resistance caused by an abundance of aquatic vegetation growing in the channel has the effect of decreasing the flow velocity of water, which in turn can increase the water's depth and enhance the chance of flooding. Particle Image Velocimetry (PIV) is a well-established technique for measuring velocity fields in macroscopic fluid systems and this image-based approach is considered a suitable method for estimating surface flow velocities (Sun et al 2010). However, very few attempts have been made to estimate surface flow velocities using PIV technology for heavily vegetated rivers. Given that aquatic plants have a significant influence on river hydraulics, it is necessary for flood control and water supply to measure surface flow velocities in vegetated rivers. This project aims to evaluate the efficacy of PIV to estimate surface flow velocities in vegetated rivers. The PIV results will be compared with those measured by an (in-situ) Acoustic Doppler Velocimeter (ADV), which is one of the most popular instruments for measuring flow velocities, to evaluate their accuracy