时空图像测速法的敏感性分析及不确定度评估

Sensitivity analysis and uncertainty evaluation of space-time image velocimetry

时空图像测速方法(STIV)是一种以测速线为分析区域、通过检测合成时空图像的纹理主方向估计一维时均流速测量方法。由于具有空间分辨率高、实时性强的优点,在河流水面流速、流量的实时监测中具有特别的应用潜力。但鉴于现场环境的复杂性和河道水流的变化性,现有研究在敏感性分析及不确定度评估方面尚存在不足,使得方法的实用性受限。对此设计了一种滚动画幅装置来模拟河流水面运动,并在此基础上全面开展了频域STIV方法的定量评估。相比数值模拟和现场比测的方法,该装置能够提供相对真实的测量环境和稳定的运动参数。实验结果表明:测速线长度和示踪条件是影响测量精度的主要敏感因素。通过合理的参数设置可以将方法的不确定度控制在±1%以内,能够满足水文测验的精度要求。

Space-Time Image Velocimetry （STIV） is a time-averaged velocity measurement method, which takes a testing line as the Interrogation Area （IA）, and detects the texture orientation of a generated Space-Time Image to estimate the 1D velocity. STIV has great potential in real-time monitoring of river flow owe to its high spatial resolution and low time complexity. However, its practicality is still limited by the deficiencies of sensitivity analysis and uncertainty evaluation due to the complexity of field conditions and the variability of river flow. To address this issue, a rolling painting device is designed to simulate the movement of river surface flow, and the quantitative evaluation of a DFT-STIV method is comprehensively conducted. Compared to the evaluations based on numerical simulation and field measuring, it provides relatively real measuring environment and stable motion parameters. Experimental results show that the length of testing line and the tracing condition are main sensitive factors of velocity measurement. With reasonable parameter settings, the uncertainty of STIV can be controlled within ± 1% , which meets the accuracy requirement of hydrometry.