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管道的当量粗糙度k是关键的水力计算参数,同时也是评估不同厂家同类管道制造加工质量的重要指标,因此对于一种新型管道,从水力学的观点,首要之事就是在水力试验室准确地率定k值。本文对3种管道进行了系统实验,结果发现用Colebrook公式确定的k值随着雷诺数Re的变化而显著变化。这是与实际相矛盾的,因为对于给定的管道在很短的时间内k应为常数。产生矛盾的主要原因就是测量参数存在不确定性。本文提出了定量计算管道阻力系数、k和流量的不确定度的方法,考虑了管径、管长、流量和水头损失以及量水堰宽度、高度与堰上水头等测量的不确定度。然后,以系统测量的实验数据为依据,研究了如何应用不确定度理论合理地确定k值及其不确定度大小。
Equivalent roughness of pipeline k is a key hydraulic calculation parameters, but also to assess the quality of different manufacturers of similar pipe manufacturing and processing an important indicator, so for a new pipeline, from the hydraulic point of view, the first thing is accurate in the hydraulic laboratory Rate k value. In this paper, three kinds of pipelines were systematically tested and found that the k value determined by the Colebrook formula changed significantly with the Reynolds number Re. This is contradictory to the reality, since k should be constant for a given pipe in a very short period of time. The main reason for the conflict is the uncertainty of the measurement parameters. This paper presents a method for quantitatively calculating the pipe resistance coefficient, k and the uncertainty of flow rate, taking into account the measurement of pipe diameter, pipe length, flow and head loss, as well as the width of weir, the height and the weir head. Then, based on the experimental data measured by the system, the paper studies how to apply the uncertainty theory to determine the value of k and its uncertainty.