Study On Hydraulic Calculation And Optimization Of Parabolic Complex Section Channel

China has a vast territory and uneven distribution of water resources.In general,China's southern regions are rich in water resources,accounting for more than 80% of the country's total water resources,while the vast northern water resources are less than 20% of the country's total water resources.In the use of water resources,agricultural water accounts for the largest proportion.At the same time,China's basic national conditions determine that agricultural irrigation is mainly used in the form of channel water delivery for a long time now.Therefore,channel hydraulic calculation and optimization is one of the important ways to improve water delivery efficiency.There are various types of sections in the channels.Reasonable selection of channel sections can not only effectively improve water delivery efficiency,but also reduce frost heaving and damage,save land and reduce construction costs.Parabolic channel is a new type of cross-section channel,which has been applied in northern China because of its good anti-frost property.However,due to its cross-sectional characteristics,the parabolic channel can be used only in small channels,whether it is designed with the best hydraulic section or the practical economic section.In view of the shortcomings of the parabolic channel not suitable for large and medium-sized channels,this paper proposes a compound cross-section channel with parabola channel slope and horizontal channel bottom.This kind of channel has the advantages of parabolic channels and can be used in large and medium-sized channels.(1)Through a large number of literature review,the paper analyzes and summarizes the commonly used channel lining anti-seepage materials and methods,the commonly used cross-section forms of channels and the advantages and disadvantages of each section,the commonly used hydraulic factors calculation methods,the channel optimization algorithms and the advantages and disadvantages of each algorithms.(2)The calculation formula of the hydraulic elements of the parabolic composite section channel is derived.The water depth,the water surface width and the horizontal bottom width are used as variables.The Lagrangian multiplier method is used to establish the iterative equation for the optimal solution.The Mathcad mathematical software is used for calculation.The relationship between flow rate and water depth and the calculation formulas of water depth,water surface width,cross-sectional area and wet period are derived for the optimal hydraulic section of the parabolic composite channel.(3)The optimal hydraulic section of the composite channel for the square parabolic slope and the horizontal channel has difficulties in construction and uneconomical.On the basis of the optimal hydraulic section,the data is fitted to obtain the best H/H0.The parabolic water surface width and water depth ratio ?=1.660 corresponding to the value,the calculation formula of the practical economic section of the parabolic composite channel is derived,and detailed calculation steps are proposed.(4)The objective function is to minimize the sum of excavation cost,filling cost and concrete lining cost and it covers all construction methods and construction costs of the parabolic composite section channel.At the same time,in order to avoid missing the feasible optimal solution,“shuffled frog-leaping algorithm”(SFLA)is used to optimize these channel models.Finally,the objective function within the range of parameters variation is represented by MATLAB 3D rainbow graph and analysis sensitive of various section parameters.