| Flow measurement in irrigation is a basic and key technology. It is important for water saving, efficient and sustainable utilization of water resources. According to the status of technology of flow measurement, to study the water equipment with a high precision, wide flow measurement range, low head loss, high sensitivity and flexible, is one of an urgent need for irrigation management technology. In recently years, the lateral channel and sublateral channel field engineering in irrigation area have been reformed, the research of flow measurement facility in small channel become the focus on flow measurement tech. In this paper, in order to solve the problem that Irrigation and field for small channels, a large amount of intake and the amount of water means lack of appropriate facilities, the author transformed the intake of channel and designed a simple structure which is side weir. Through the method of theory analysising and prototype experiment and numerical simulation, the hydraulic performance and influencing factors of side weir had been researched. Prototype testing were developed in length 35 m, width 0.5m, 0.6m deep at outlet flat rectangular channels and side slope channels, and installed 0.5cm thick slice of 18 kinds(6 kinds of weir height: 7.05 cm, 10.25 cm, 13.15 cm, 15.15 cm, 17.05 cm, 20.35 cm, 3 kinds of weir width: 50 cm, 40 cm, 30cm). 10 kinds different side weir flow conditions were tested hydraulic performance, a total of 188 groups. Through studying on relationship between downstream water line, section depth, velocity, Froude number equal amounts with the side weir structure’s parameters. There can make the following main conclusions:1. Through experiments and theoretical analysis, the flow formula based on freedom of the front weir formula thin-wall rectangular side weir in rectangular channel is meet to the dimensional harmony. The flow formula is concise and practical, has high accuracy flow measurement, it average relative error is 2.05%;2. Surface line of Thin-wall rectangular side weir is more complex, the main water line to the nearby channel weir showed increased gradually at first and then decreased. There has a high Critical submerged degree on side weir, Critical submergence degree range of 0.71 to 0.91, its’ average degree can reach on 0.78.Thin-wall rectangular side weir can ensure freedom in a wide range of work under the current state. Side weir backwater height higher compared to the amount of the sink, under the test conditions, when the flow rate at 15 L / s ~ 41 L / s range, backwater height is all less than 20 cm, maximum backwater height is 19.46 cm. The upstream Froude number Fr of Thin-wall rectangular side weir is all less than 0.3, in line with the amount of irrigated water standards. The head loss is relatively high, accounting for about 50% of the total head upstream, and higher than the amount of water more groove type devices. For rectangular thin-walled rectangular side weir on the gentle slope of the weir channel wide choice should take greater width on principle as well; at the weir height of choice, should choose a low height under the premise does not affect the accuracy of flow measurement side weir.3. By FLOW-3D software to simulate the hydraulic performance under test conditions rectangular side weir channel, by comparing simulation results with experimental results obtained simulate the flow regime, changes in the water line and velocity distribution, there are good agreement with experimental results shows numerical simulation model uses reliable, accurate simulation results can be further simulation study other side weir shape hydraulic performance through values, which provides a reference for the side of the weir shape optimization.By studying hydraulic performance in thin-wall rectangular side weir on rectangular channel, it can be proofed that thin-wall side weir is a description of a suitable water flow measurement on small channels, there have a good promotion prospects. |
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