Sensitivity study of large-scale particle image velocimetry measurement of river discharge using numerical simulation
Sensitivity study of large-scale particle image velocimetry measurement of river discharge using numerical simulation
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DOI：
10.1016/j.jhydrol.2007.10.062
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发表时间：
2008-01-30
影响因子：
6.4
通讯作者：
Belleudy, Philippe
中科院分区：
文献类型：
--
作者：
Hauet, Alexandre;Creutin, Jean-Dominique;Belleudy, Philippe
本文研究了河流中大尺度粒子图像测速（LSPIV）测量的不确定性。LSPIV属于河流局部遥感方法，如基于雷达和激光雷达的技术。与传统的河流测量相比，这些方法有许多潜在的优点，但它们有一个根本的缺点：它们是间接测量。因此，需要参照直接测量结果对其进行评估。第一种验证方法包括在现场和实验室实验中将LSPIV测量结果与经典测量结果进行比较。不幸的是，在这两种情况下，它是不可能在实践中控制，所有的参数，并区分各种误差sources.In本研究中的影响，我们提出了一个更理论的评估LSPIV潜在的通过数值模拟。这个想法是简单地用数学公式表示测量的当前知识状态，包括现象的物理学（被照亮的河流）和传感器的物理学（相机和PIV跟踪）。何时开始此类模拟的困境如下：如果我们能够验证模拟，则模拟是令人满意的，这意味着能够在广泛的条件下比较模拟和观察结果。模拟对于获得有关最重要的测量条件的初步见解非常有用，以组织验证研究。我们的模拟器由三个块组成：（1）河流块通过关联EDM模型和给出3D速度分布的理论垂直速度剖面来表示单向河流流量。该水力模型由代表自由表面示踪剂的特征、自由表面的照明（阴影和太阳反射）和风的影响补充。(2)摄像机模块根据摄像机的内参数和外参数将河流状态参数转换为光栅图像。(3)LSPIV分析模块执行经典的LSPIV分析，包括图像的几何变换，PIV分析以获得表面速度场，以及流量计算。我们试图在模拟器的不同模块之间保持良好的平衡（即不使一个组件比其他组件复杂得多）。模拟器在其不同模块的开发过程中进行了部分测试，然后进行全局验证。它很好地再现了用Hauet等人的实时连续系统进行的现场LSPIV实验中观察到的变化性[Hauet，A.，克鲁格，A.，克拉耶夫斯基，W.，布拉德利，A.，穆斯特，M.，Credier，J.D.，威尔逊，M.，2008.基于图像的实时流量估计实验系统。水文工程学报（Journal of Hydrologic Engineering）模拟器还可以用于检查不同的场景，并评估不同误差源的相对重要性。通过两个例子，我们说明了这种能力的模拟器，以评估一个给定的误差源的相对权重，并测试一个新的配置的测量。(c)2007 Elsevier B.V.保留所有权利。
This study deals with the uncertainty of large-scale particle image velocimetry (LSPIV) measurements in rivers. LSPIV belongs to the methods of local remote sensing of rivers, like Radar- and Lidar-based techniques. These methods have many potential advantages, in comparison with classical river gauging, but they have a fundamental drawback: they are indirect measurements. As such they need to be assessed in reference to direct measurements. A first validation method consists in the comparison of LSPIV measurements with classic gauging results, in field and laboratory experiments. Unfortunately, in both cases, it is impossible in practice to control, all the parameters and to distinguish the impact of the various error sources.In the present study we propose a more theoretical assessment of LSPIV potential through numerical simulation. The idea is simply to mathematically formulate the present state of knowledge of the measurement including both the physics of the phenomenon (the illuminated river) and the physics of the sensor (the camera and the PIV tracking). The dilemma about when to start this type of simulation is the following:The simulation is satisfactory if we can validate it which means to be able to compare simulations and observations over a wide range of conditions.The simulation is useful to get preliminary insights about the most important measurement conditions to organize validation studies.Our simulator is composed of three blocks:(1) The river block represents the unidirectional river flow by the association of the EDM model and a theoretical vertical velocity profile giving a 3D velocity distribution. This hydraulic model is complemented by features representing free surface tracers, the illumination of the free-surface (shadows and sun reflection) and the effect of the wind.(2) The camera block transforms the river state parameters into raster images according to the intrinsic and extrinsic parameters of the camera.(3) The LSPIV analysis block performs a classical LSPIV analysis, including geometric transformation of the images, PIV analysis to obtain a surface velocity field, and discharge computation.We tried to keep a good balance between the different blocks of the simulator (i.e. not to make one component much more sophisticated than the others).The simulator was partly tested during the development of its different blocks, and then globally validated. It reproduced well the variability observed in the field LSPIV experiments conducted with the real-time continuous system of Hauet et al. [Hauet, A., Kruger, A., Krajewski, W., Bradley, A., Muste, M., Creutin, J.D., Wilson, M., 2008. Experimental system for real-time discharge estimation using an image-based method. Journal of Hydrologic Engineering]. The simulator can also be used to check different scenarios and to assess relative importance of the different sources of error. With two examples, we illustrate this capability of the simulator to assess the relative weight of a given error source and to test a new configuration of measurement. (c) 2007 Elsevier B.V. All rights reserved.