自由溢流渠道末端深度法水文液体流量测量

[中文适用范围]： 本文件规定了一种在平滑、基本水平的渠道（或缓坡渠道）中估计清水亚临界流量的方法，该渠道在底部被水工结构突然中断，具有垂直落差并自由排放。 这种溢流形成控制部分，并提供使用末端深度测量方法估计流量的方法。 已经研究了各种具有溢流的河道横截面，但仅考虑那些经过充分研究和测试后获得普遍接受、因此不需要现场校准的河道横截面。 本文件涵盖具有以下类型横截面的渠道： a) 具有受限和非受限推覆层的矩形； c) 三角形； e) 抛物线。 b) 梯形； d) 圆形；边缘处的流动是曲线的；因此，测量的液滴深度并不等于基于平行流假设的原理计算出的临界深度。 然而，末端深度和临界深度（如平行流假设的情况）具有唯一的关系，用于估计通过这些结构的流动。 [外文原描述]： ISO 18481:2017 specifies a method for the estimation of the sub-critical flow of clear water in a smooth, essentially horizontal channel (or a gently sloping channel), abruptly discontinued at bottom by a hydraulic structure, with a vertical drop and discharging freely. Such an overfall forms a control section and offers a means for the estimation of flow using the end depth measurement method. A wide variety of channel cross-sections with overfall have been studied, but only those which have received general acceptance after adequate research and testing, and therefore do not require in situ calibration, are considered. This document covers channels with the following types of cross-sections: a) rectangular with confined and unconfined nappe; b) trapezoidal; c) triangular; d) circular; e) parabolic. The flow at the brink is curvilinear; therefore, the measured depth at the drop is not equal to the critical depth as computed by the principle based on assumption of parallel flow. However, the end depth and the critical depth (as in the case of the assumption of parallel flow) have unique relation, which is used to estimate the flow through these structures.