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

水生植物普遍存在于低地河流中，它们对河流水力学起着主导作用。流动阻力（通过曼宁粗糙度系数）已被证明随着大型植物的生长而发生季节性变化，在水柱中水生植物更丰富的时期，曼宁系数的值往往更高（Naden et al . 2006）。水道中大量的水生植被增加了流动阻力，从而降低了水流速度，从而增加了水的深度，增加了洪水发生的机会。粒子图像测速（PIV）是测量宏观流体系统速度场的成熟技术，这种基于图像的方法被认为是估计表面流速的合适方法（Sun et al . 2010）。然而，很少有人尝试使用PIV技术来估计植被丰富的河流的地表流速。由于水生植物对河流水力学有重要影响，因此在防洪供水中测量植被河流的地表流速是必要的。本项目旨在评价PIV在植被河流中估算地表流速的有效性。PIV结果将与原位声学多普勒测速仪（ADV）测量的结果进行比较，以评估其准确性，ADV是测量流速最常用的仪器之一

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