Research On Hydraulic Performance And Standardization Of Water-measuring Column With Round Head In U-shaped Channel

In China Irrigation Area, water channel is the main water conveyance form for farmland irrigation. Carrying out water-measuring work in water delivery channel system can ensure the correct water diversion, water distribution and water use. At the same time, it can enhance people’s awareness of water conservation and has important significance to solve the problem of agricultural water-measuring. Therefore, research on water-measuring facilities and put it into standard application has become an important means for effective water management. Under specific situation, these water-measuring facilities should have advantages like simple structure, high measuring accuracy as well as good adaptability to water-measuring work.Water-measuring column with round head is a new equipment for flow measurement applicable to irrigation region in our country. The streamlined structure design and V-shaped empennage makes water flowing smoothly and steady along the flume. It can improve the flow pattern and reduce head loss effectively compared with the ordinary cylindrical measuring flume. In this study, physical model tests and computer numerical simulation was combined to analyze the hydraulic performance and structure of the water-measuring column with round head in U-shaped channel under different slope conditions. Based on the above study, standardization selection program was obtained. The main research contents and conclusions are as follows:(1) To study the general flow measurement theory of water-measuring column with round head in U-shaped channel, and deduced its critical depth theoretical flow calculation formula based on critical flow principle.(2) The experiment program was conducted with 6 throat contraction ratios, 3 aspect ratios. And the tests were carried out under 6 channel slopes and 5 discharge conditions. The author analyzed the variation of surface profile and associated hydraulic characteristics parameters. Surface profile variation of water-measuring column with round head in U-shaped channel is consistent with the hydraulic phenomenon deduced by the theory of open channel steady non-uniform gradually varied flow. The stagnation-point water depth and the discharge have a good exponential correlation. Water-measuring column with round head possess excellent hydraulic performance, such as: small upstream backwater and Froude number which is less than 0.5, a high critical submergence degree up to 0.90, small water head loss. The fitted flow formula under the basis of stagnation-point water depth has a good flow measurement accuracy and could meet the irrigation requirements(<5%), which is obtained through compare demonstration with the measured discharge.(3) Software Flow-3D and the RNG k-ε turbulence model were used to simulate the three-dimensional water flow field of water-measuring column with round in U-shaped channel. Comparison of physical model test results with numerical model test results showed that: they have good consistency. Time-averaged flow field and V-shaped empennage of water-measuring column with round head for flow measurement were analyzed after numerical simulations. The flow field of water-measuring column with round head for flow measurement in U-shaped channel with different section size was solved out.(4) Selection range of optimal type parameters of water-measuring column with round head was determined through the comprehensive analysis which combined physical model tests and three-dimensional numerical experiment. That is: Suitable range of throat contraction ratio is between 0.50 to 0.70, and it is ultimately determined by the channel slope. When the channel slope is small, the throat contraction ratio should be bigger; and when the channel slope is big, the contraction ratio should be smaller. The advised range of the aspect ratio of water-measuring column with round head is in 3/2~2. The aspect ratio ? should corresponding increase when the throat contraction ratio is decrease,but should not be more than 5/2.(5) Standardization selection mode of water-measuring column with round head in U-shaped channel was concluded on the basis of standardization theory; Flow formula which is more practical was set up; Naming method of series water-measuring column with round head was given and a specification on water-measuring column was formed; Suitability of water-measuring column with round head was analyzed based on the above conclusions.