| Promoting the development of water-saving agriculture, we must rely on the accurate measurement of water level and discharge, and measuring water of irrigation is just the effective means to provide these materials. The arc-based trapezodoil canal section is derived in the form of a trapezoidal cross-section, with the strong flow capacity, small head loss, strong anti-frost capacity, difficult to siltation, and many other advantages. Therefore the arc-based trapezodoil canal is constantly promote in the renovation project of irrigation districts. Based on the fluent software, the numerical simulation has been carried out to the new non-throated flume of arc-based trapezodoil canal. Using RNG k-ε turbulence model and VOF approach to the free surface, the paper discusses the upstream backwater height, Froude number, critical submergence degree, head loss, flow measurement accuracy under different parameters by analyzing different contraction ratio and throat slope coefficient. And on this basis, the paper optimizes the analysis of body flume parameters, determine the best range in shrinkage ratio and throat slope coefficient. These studies have widely promoted value in irrigation area of application. The main contents and conclusions are as follows:(1) Based on the measuring principle of arc-based trapezoidal canal and cut-throat flow measurement flume, flow equation is established by regression analysis to fit with the upstream water level, measuring flume throat width, shrinkage ratio and the average calculation error of 2.76% meet the flow measurement accuracy.(2) The paper selects flow measurement flume with different contraction ratio and throat slope coefficient to develop pilot programs and three-dimensional numerical simulation in a wide range of bottom slope.On this basis, the results show that the numerical model and simulation parameters selection are provided with high reliability.And using numerical simulation method can be a true reflection of different flow conditions the amount of vertical and horizontal drainage groove section and the internal surface line velocity field variation. This paper analyzes the the flow pattern from the froude number and specific energy curves, and the results show that critical depth occurs in the divergence zone section of measuring flume, from the throat section between 0.51 ~ 1.52 m, the first half at the outlet diffuser section, and the location of critical depth move backward with over-current flow increasing.(3) Based on the numerical experiments of arc-based trapezoidal canal and cut-throat flow measurement flume, the paper focuses on flow measurement factors and parameters of the non-throated flume and analyze the hydraulic theory and data.The results show that flow measurement increases with the increasement of channel slope coefficient and the shrinkage ratio. The impact of channel depth and throat slope coefficient can be ignored. The backwater height of measuring flume is small, the upstream section froude number is less than 0.5, critical submergence degree is up to 0.92, and head loss average for 3.65% of the total head upstream.(4)The paper obtains the relationship between upstream water level and discharge in different shrinkage ratio, throat slope coefficient and channel bottom slope by comprehensive analysis of experimental data. And then gives the optimal range of parameter selection. Shrinkage ratio of measuring flume is suitable in the range of 0.6 to 0.75, and the specific choice depends on the size of the channel bottom slope; The relationship between throat slope coefficient and channel slope coefficient is m1 =(0.7 ~ 1) m. Combined with previous research results under different channel sizes and bottom slope, the paper obtains appropriate size parameters of Arc-based trapezoidal canal and cut-throat flow measurement flume. And it defines the scope of the flow measurement flume. |
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