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首页> 外文期刊>Experiments in Fluids: Experimental Methods and Their Applications to Fluid Flow >Error analysis of 3D-PTV through unsteady interfaces
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Error analysis of 3D-PTV through unsteady interfaces

机译：通过非定常接口的3D-PTV误差分析

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The feasibility of stereoscopic flow measurements through an unsteady optical interface is investigated. Position errors produced by a wavy optical surface are determined analytically, as are the optimal viewing angles of the cameras to minimize such errors. Two methods of measuring the resulting velocity errors are proposed. These methods are applied to 3D particle tracking velocimetry (3D-PTV) data obtained through the free surface of a water flow within a cavity adjacent to a shallow channel. The experiments were performed using two sets of conditions, one having no strong surface perturbations, and the other exhibiting surface gravity waves. In the latter case, the amplitude of the gravity waves was 6% of the water depth, resulting in water surface inclinations of about 0.2.. (The water depth is used herein as a relevant length scale, because the measurements are performed in the entire water column. In a more general case, the relevant scale is the maximum distance from the interface to the measurement plane, H, which here is the same as the water depth.) It was found that the contribution of the waves to the overall measurement error is low. The absolute position errors of the system were moderate (1.2% of H). However, given that the velocity is calculated from the relative displacement of a particle between two frames, the errors in the measured water velocities were reasonably small, because the error in the velocity is the relative position error over the average displacement distance. The relative position error was measured to be 0.04% of H, resulting in small velocity errors of 0.3% of the free-stream velocity (equivalent to 1.1% of the average velocity in the domain). It is concluded that even though the absolute positions to which the velocity vectors are assigned is distorted by the unsteady interface, the magnitude of the velocity vectors themselves remains accurate as long as the waves are slowly varying (have low curvature). The stronger the distur
机译：研究了立体流量测量通过不稳定光学接口的可行性。通过波动光学表面产生的位置误差是分析地确定的，因为相机的最佳观察角度是最小化这种误差。提出了两种测量所产生的速度误差的方法。这些方法应用于通过与浅通道相邻的空腔内的水流的自由表面获得的3D粒子跟踪速度（3D-PTV）数据。使用两组条件进行实验，一个没有强表面扰动，另一组具有强大的表面扰动，以及其他表现出表面重力波。在后一种情况下，重力波的幅度为水深的6％，导致水面倾斜约0.2。（在本文中使用水深作为相关长度尺度，因为测量在整个中进行水柱。在更常规的情况下，相关刻度是从接口到测量平面的最大距离，这里与水深相同。）发现波浪对整体测量的贡献错误很低。系统的绝对位置误差是适度的（1.2％的H）。然而，鉴于从两个帧之间的粒子的相对位移计算速度，测量的水速度中的误差合理地小，因为速度中的误差是平均位移距离上的相对位置误差。测量相对位置误差为0.04％H，导致自由流速度的0.3％的小速度误差（相当于域中平均速度的1.1％）。结论是，即使速度矢量被分配的绝对位置是由不稳定的界面扭曲的，只要波浪缓慢变化（具有低曲率），速度向量本身​​的大小保持精确。剧烈越强

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