| 底坡对U形渠道量水平板测流影响分析 |
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| 作者单位： | ;1.西北农林科技大学旱区农业工程教育部重点实验室 |
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| 摘 要： | 【目的】量水平板具有构造简单、不易淤积等优点,虽已建立流量与平板偏转角、上下游水深及板型等因素的关系式,但底坡对量水平板水力特性的影响还缺乏系统研究,有必要深入分析,以提高量水平板测流公式的适用范围。【方法】以北方灌区常见U形渠道为试验水槽,选择断面最佳收缩比0.439的U形渠道量水平板为试验对象。通过设置3种水槽底坡(0.000 2～0.001)和4～7种流量(10～44 L/s)共18种试验工况,分析了各工况下水面线和平板偏转角的变化规律,研究了底坡对水面线、相对水头损失、能量转化系数、平板偏转角度和综合流量系数的影响。基于闸孔淹没出流公式,拟合出含底坡变量i的半经验流量公式。【结果】在相同流量情况下,板后水跃长度、能量转化系数以及综合流量系数随底坡增大而增大;水面线、相对水头损失和平板偏转角度均随底坡增大而减小;在试验流量范围内,拟合流量公式的平均相对误差为2.6%,最大相对误差为6.5%,满足灌区量水要求。【结论】底坡对U形渠道量水平板测流影响显著,建立了包含渠道底坡的U形量水平板测流公式,提高了其适用性。
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| 关 键 词： | U形渠道 量水平板 流量公式 底坡 |
Impact of Bed Slope on Accuracy of the Horizontal Plate for Measuring Water Flow in U-Shaped Channels |
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| Institution: | ,Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas,Ministry of Education, Northwest A&F University |
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| Abstract: | 【Background】Most irrigation districts in northern China are flatten and water in their channels is muddy. Existing facilities for measuring water flow in channels could cause backward water flow in their upstream and are prone to sediment deposition. Horizontal plate is a new and simply structured facility to measure water flow and can alleviate sediment deposition. While the impact of the discharge and other factors such as plate deflection angle, water depth in both upstream and downstream, and plate profile on performance of the plate method has been well documented, how bed slope of a channel affects hydraulic characteristics of the plate remains poorly understood.【Objective】The purpose of this paper is to plug this knowledge gap, systematically investigating the effects of bed slope on reliability and accuracy of the horizontal plate for measuring water flow.【Method】U-shaped channel commonly used in irrigation areas in northern China was taken to test the method, and the volume of the horizontal plate with optimal contraction ratio of cross-section(0.439) was selected as the test object. With a total of 18 combinations, which included three bed slope ranging from 0.000 2 to 0.001 with each associated with 4～7 flow rates ranging from 10 to 44 L/s, variation of the water-surface line and the plate deflection angles in each combination were measured, from which we analyzed the impact of the bed slope on water-surface line, relative water head loss, energy conversion coefficient, plate deflection angle and comprehensive flow coefficient. Using the formula of sluice flooding discharge, a semi-empirical flow formula with the bed slope as independent variable was used to fit the data.【Result】Under the same water flow rate, the hydraulic jump length behind the plate, the energy conversion coefficient and the comprehensive flow coefficient all increased as the bed slope became steeper; in contrast, the water-surface line, the relative water head loss and the plate deflection angle all decreased as the bed slope increased. For all tested flow rates, the average relative error of the fitting formula for water flow rate was 2.6%, with a maximum of 6.5%, meeting the requirement for water flow in irrigated areas.【Conclusion】The bed slope of channel has a significant influence on accuracy of the horizontal plate for measuring water flow in U-shaped channels, and a formula considering the bed slope was proposed to calculate water flow in U-shaped channels. |
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| Keywords: | U-shaped channel volume level plate flow formula bed slope |
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