中文摘要：

用粒子示踪技术测量明渠挟沙水流中固相颗粒的速度时，流速梯度和浓度梯度的存在会引起测量误差。选用典型的垂线流速与浓度分布公式对时均速度测量误差进行分析，得出了误差的解析表达式。对该解析式的理论分析表明，测量误差恒小于零，即速度测量值比实际值偏小。误差的大小与采样窗口的相对位置、尺寸及颗粒的悬浮指数有关。对误差大小随自变量的变化规律进行的数值分析结果表明，在一定的流场条件下，测量误差的最大值出现在床面附近，误差从床底至水面呈现出先减小后增大的特点。

英文摘要：

The presence of concentration gradients shifts the effective location of the reported mean velocity away from the sampling bin＇s center in sediment-laden flow measurement with particle tracking velocimetry. Under typical velocity and concentration profiles for open channel flows, the bias error proves to be constantly less than zero, leading to an underestimate of the actual velocity. The error is closely related to three variables which are the relative location of the flow, the size of the sampling bin, and the suspension index of the sediment particles. Numerical analysis shows that the magnitude of the error follows a first-decrease-then-increase pattern from the bottom to the water surface along the vertical.