Experiment And Numerical Simulation Of Semicircular Cylinder Measuring Flume In U-shaped Channel

Flow measurement in channels play an important role in strengthening water management as well as collecting water resources fee in the irrigation region, and it is an important means to promote the water-saving agriculture. At present, there is many irrigation region in China. However, the irrigation region of North and South differ widely in the type of channel and the hydrological conditions, in particular conditions of diversity regions. So, the flow measurement technique are in high demand. The U-shaped channel has been widely used in the last irrigation canal system rehabilitation, such its importance increases continuously. It is necessary to develop a new measuring water devices. The semicircular cylinder measuring flume consist of a semicircular cylinder-shaped columniation in channel. It has the advantages of simple structure, durable, high accuracy and well suited to measuring flume in the U-shaped channel. Therefore, it has much value to promote the semicircular cylinder apply in the U-shaped channel with gently slope and sediment-laden water in the irrigation region of North. In this paper, based on the study of the hydraulic characteristics, experimental research is conducted on the semicircular cylinder measuring flume in the U-shaped channel, and the Flow-3D software was used to simulate the semicircular cylinder measuring flume in the U-shaped channel(D40). The main research contents and conclusions are as follows:(1) The structure and the flow measurement theory of the semicircular cylinder measuring flume in the U-shaped channel with two types is analyzed, its critical depth calculation formula depend on a theory of “Minimum Specipic Energy” is derived, and two kinds of flow calculation formula is deduced.(2) The experiment was conducted with different types and contraction ratios for the semicircular cylinder measuring flume, in order to explore the change law of upriver water depth, critical depth, Froude number, critical submerged criterion, backwater depths and head loss. The results show that the semicircular cylinder measuring flume in the U-shaped channel has the advantages of high critical submerged criterion, small backwater depths and head loss. A good relationship exists between upriver water depth and critical depth, the flow calculation formula is of high precision by dimensional analysis. In cases where the semicircular cylinder radius being equal, the semicircular cylinder measuring flume without sill is better than that it with sill, and the results show that the suitable type is no sill type, it is suggested that suitable contraction ratios range of the semicircular cylinder measuring flume in the U-shaped channel is 0.36~ 0.52.(3) By modeling the semicircular cylinder measuring flume in the U-shaped channel(D40) with different contraction ratios, the true VOF method and the RNG k-ε turbulence model was used to simulate the semicircular cylinder measuring flume in the U-shaped channel(D40) based on Flow-3D software, and the hydraulic characteristics were analyzed. Compared the simulated value with the measured value, the results show that the numerical simulation method could be effectively simulate the three-dimensional flow model of the semicircular cylinder measuring flume, and it provide a new method to optimize the structure of the measuring flume.