Study Of An Integrated Device For Intelligent Measurement And Control Of Flow In U-shaped Channels

It’s necessary to realize the automatic measurement of the channel water volume because of the lack of measurement and control integration equipment in Chinese rural channels and the following levels of channels which is valuable to the water conservancy information and modern management level in the irrigation area.Canal system buildings such as diversion gate and controlling gate can control channel flow.Utilizing canal system buildings to measure flow has the advantages of small head loss and low investment which can also realize measurement and control integration.In this paper,an integrated measurement and control device is developed for the common U-shaped channels in irrigation areas,and three contraction ratios of arc bottom bulkhead gate are designed according to the section size of the U-shaped channel.Through theoretical analysis,laboratory model test and numerical simulation,the hydraulic performance of arc bottom bulkhead gate in U-shaped channels under different flow rates and slope conditions is systematically studied,and the flow measurement and control model is established.Compiled the supporting intelligent measurement and control software;the suitable hardware configuration of flow measurement,power and control modules is determined by comparison,then the measurement and control integrated device is tested in the field.The main research contents and conclusions are as follows:(1)The design of measurement and control integrated device in U-shaped channel is composed of flow measurement module(arc bulkhead gate and pier,water level sensor and gate opening sensor),flow control module(driving device,motor motion controller,transmission device),control box and bracket.The main functions,components and connection modes of each component are determined.(2)The critical relative opening e/H of orifice flow and weir flow of arc bulkhead gate in U-shaped channel is different from the traditional discriminant threshold.The critical relative opening of the gate with three kinds of contraction ratio is above 0.92,and the larger the contraction ratio is,the larger the e/H is.When the contraction ratio is 1:1,the e/H changes little with the increase of the flow rate and can be considered equal to 1 while the water level in front of the gate and behind the gate are basically equal.(3)The variation law of the surface line distribution,Froude number distribution,head loss and critical submerged criterion of the arc bottom bulkhead gate with different bottom slope,gate width,submerged criterion,flow rate and gate opening in U-shaped channel.The average relative error is less than 3.37%,which can meet the water quantity requirement of irrigation area.In practical application,it is recommended to choose the arc bottom bulkhead gate with contraction ratio of 1:1 and the channel with bottom slope less than 1/1000 for flow measurement.(4)Flow-3D software was used to simulate the arc bottom bulkhead gate under different gate openings in U-shaped channels.The simulation results were consistent with the experimental results.On this basis,the flow field distribution of the arc bottom bulkhead gate in U-shaped channel was further analyzed,and the analysis results of velocity distribution,Froude number,turbulent kinetic energy and head loss of the arch bottom flat gate were obtained.The velocity distribution in front of the gate with different gate openings is consistent,and the maximum velocity is located at the vertical line,below the center of the water surface.The Froude of the upstream flow is less than 0.5,which meets the flow measurement conditions.The Froude changes before the gate as it is not suitable for flow measurement.The maximum turbulent kinetic energy in front of the gate is located at the junction of the side and the water surface,and the area of large turbulent kinetic energy is concentrated at the side.(5)The hardware configuration of the measurement and control integrated device was determined by selection and comparison,and the program design of the measurement and control module was completed.After completing the device,the average relative error of flow measurement is 2.22%,which meets the requirements of flow measurement in irrigation area.