Numerical Simulation On Hydraulic Performance Of Short-throat Flume In Arc-based Trapezoidal

In order to promote the water conservation better,implement the metering irrigation and reduce the burden of farmers,it is necessary to strengthen the management of water,the most fundamental and critical technology is the measuring water of irrigation.The channels in trapezoidal section with curved slpo toe and arc-based trapezoidal have excellent capacity of flowing and water traansport,the sedimentation status,distribute of structure and stress are better than the trapezoidal channels.Due to the lack of adequate water facilities,development of appropriate amount of water facilities has practical value to promote the modernization of irrigation management.In view of the characteristics of two channels,author disign the short-throat flow measurement flume of arc-based trapezoida,based on Fluent6.3,using RNG three-dimensional turbulence model and the VOF(volume of fluid)method to track the free surface,the three-dimensional flow field simulation of the hydraulic performance of the flume is carried out.It is concluded that the short-throat flume in arc-based trapezoidal showed closer hydraulic characteristics in two channels,practicality both well,provides a theoretical basis for the future using and large-scale promotion of such measuring flume in the actual irrigation area.The paper mainly discussed the following aspects:(1)The numerical simulation calculation of water flowing characteristics under different bottom slope with the combination of different shrinkage ratio and throat length is carried out.By comparing the calculated value from Xie Cai formula with simulated values from Fluent,it is found that the numerical model and the established geometric model are accurate,means the method of numerical simulation can be used to analyzed the water flowing characteristics accurately.(2)The hydraulic performance of the water flowing and water surface line,the Froude number before the flume and along the flow were obtained under different working conditions,as well as the influence factors such as the head loss were studied.A flow formula related to the water level upstream of the channel,the shrinkage ratio of the water tank,the width of the throat,and the length of the throat is established for the arc-based trapezoidal channel with a high curvature,and the accuracy is relatively high,which meets the requirements for the quantity of water in the irrigation area.(3)The hydraulic performance of the water flowing and water surface line,velocitydistribution from cross section were obtained under different working conditions.Based on the comparative analysis of the Froude number along the section and the section ratio energy,it was found that the position of the critical depth section was the diffusion section in the measuring flume,and the increase of the throat length leads to the location of the occurrence moved backwards.The influence factors of relation curve of water discharge,flume backwater height are discussed in this paper.A flow formula related to the water level in the upper reaches of the channel,the shrinkage ratio of the measuring flume,the width of the throat,and the length of the throat is established for the channels in trapezoidal section with curved slpo toe with a high accuracy and meets the requirements for the quantity of water in the irrigation area.(4)Through the verification of other channels,it is concluded that the formula is universal,which provides the basis for the follow-up of other types or specification sinks.In the process of the study,there are some shortcomings due to the limitation of time and personal ability: the hydraulic performance of the short-throat flume in arc-based trapezoidal based on the numerical simulation method is studied,lacking of comparation of the hydraulic model test and the actual application in the irrigation area.Later,suggested to finish the flume structure optimization and combination with the engineering practice,provide the further correction in the current formula;In the process of numerical simulation,the influence of sediment and floating material are not taken into account.In the later period,the influence of sediment on over current characteristics and the corresponding measures for anti silting should be further studied.The formula flow formula only under the free flow condition is mainly carried out.After derivation,it is suggested that the later supplement of submergence flow correlation flow measurement formula;When the flow formula is universality verified,there is no enough discussion of the corresponding bottom slope range of the different shrinkage ratio.