| The current shortage of water resources, soil and water misallocation under irrigation water use efficiency is not high grim situation, the efficient use of water resources has an important strategic position and role. Thus increasing the amount of irrigated water channel technology becomes necessary. U-shaped channel is China’s first cross-section in the form of channels. Because of its water capacity, located close to the optimal hydraulic cross section, hydraulic conditions, not easy to siltation, and good anti-frost, so universal use, the amount of water equipment research and development on the U-shaped channels to become a trend. Domestic scholars and experts on the amount of sink a lot of research, and developed a variety of measuring flume, but there are some more or less inadequate. In this paper, two sizes D40 and D60 semi-cylindrical channels were used four kinds of tank volume shrinkage ratio model test, and the test data were analyzed, results showed that:(1) according to a Venturi-type measuring flume measuring principle, using the energy equation and the critical flow equation, a U-shaped channel semi-cylindrical measuring flume flow measurement theory formula, the formula quantities clear, empirical formula of flow coefficient by experiment data obtained.(2) critical depth, the upstream head upstream water depth showed excellent linear relationship with the measured water depth upstream flow also showed good power function. According to the principle of harmony dimension, it launched a critical depth measuring flume relative to the amount of the water tank upstream relative depth for function formula, fitting out of the semi-cylindrical tank volume flow equation has dimension of harmony, the formula correlation coefficient R ^ 2 = 0.9984, simple and practical, high precision flow measurement, the average absolute error was 2.72%, to meet the amount of irrigated water flow measurement device specifications.(3) the amount of the water tank upstream Froude number Fr 0.45, open channel to meet regulatory requirements. Contraction than in the case with the same flow rate is inversely proportional relationship, that with the increase of flow rate decreases, and the related contraction ratio, the greater the shrinkage ratio, Fr well. Due to a linear function of U-shaped cross section area of the channel is not water depth, Froude number Fr and flow-related, with increasing flow rate decreases, but the linear relationship is not obvious.(4) U-shaped channel semi-cylindrical tank volume critical submergence degree range of 0.8 to 0.93, a mean of 0.85, the highest value is 0.93. Therefore, greater freedom of the flow range, easy to cause flooding of streams, ensuring the flow measurement accuracy.(5) with the backwater flow increases, with the contraction ratio decreases, so the actual application process should choose a larger contraction infer sink. But not too large, otherwise it will affect the flow measurement accuracy. Local head loss caused by the semi-cylindrical tank volume is small and increases with increasing flow rate, with the contraction ratio increases and decreases, accounting for upstream water head ratio is small.(6) through two specifications U-shaped channel of semi-cylindrical measuring flume test, a comprehensive analysis of the amount of the semi-cylindrical tank hydraulic performance, the U-shaped channel obtained a semi-cylindrical tank suitable amount of shrinkage ratio of 0.48 to 0.59.(7) the iteration formula and the amount of the semi-cylindrical surface of the sink in the amount of standardized design sink half cylinder radius is calculated to provide a theoretical basis for the amount of the semi-cylindrical tank template production process, the amount of the semi-cylindrical tank in the field the actual use of the foundation.U-shaped channel having a semi-cylindrical tank volume flow formula is simple and convenient for people to grasp, superior hydraulic performance, simple structure, easy construction, and simple templates to create, therefore, the amount of the semi-cylindrical tank having a value in irrigated promotion. |
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