Study On Hydraulic Analysis And Optimum Design Of Pipe Networks For Microirrigation

With the development of industry and agriculture and increase in population, the water consumption in rural areas and cities will increase constantly, and a severe shortage of water resources will exist in the future. Developing efficient agricultural water-saving techniques will be an essential strategic step to lessen the shortage of water resources and ensure the sustainable economic development of China, a large agricultural country. With the development of efficient agricultural water-saving techniques, the microirrigation technique will be rapidly developed and applied. Meanwhile, the investment in building and running the microirrigation pipe networks will increase in the whole country. Seeking the optimum plan of microirrigation pipe networks with the higher irrigation quality, lower cost of investment and lower consumption of energy can produce great benefits in economy by using the optimal design theory, methods and tools.However, the present study on hydraulic analysis and optimum design for laterals is still based on some approximate presupposition, the optimisation for submain units focuses on the distributive rate of the allowable pressure deviation without systemic and unitary optimisation, the optimisation for main pipe networks focuses on the efficient algorithm, but the applied research on microirrigation pipe networks are insufficient, and the softwares that can be reliably and widely applied to pipe networks optimization are difficult to find. Aimed at the problem and insufficiency of hydraulic analysis and optimum design for microirrigation pipe networks, several problems have been solved in this paper.The hydraulic analysis and optimal design models for single, two and equal outflow laterals are created, and solutions have been put forward. These methods are suited to resolve all kinds of problems with hydraulic analysis and optimal design for laterals, and the existing laterals can be analyzed and checked. The hydraulic analysis and optimal design models under different conditional submain units are created, and the solutions have been put forward. According to these models, the submain units are regarded as a whole and the uniformity or percentage of discharge deviation and designed discharge of irrigator are taken as restraining parameter to optimisation. Meanwhile, the equal outflow presupposition of laterals and submains are no longer adopted, so the computational procedure is simplified and computational accuracy is improved.The between of uniformity and operating pressure of irrigators, gradient, exponent of flow form, spacing between irrigators, clogging conditions, percentage of discharge deviation, lateral diameter and length are analysed and studied. The results indicate that the variation of clogging percentage is the most sensitive factor to uniformity, and the variation of percentage of discharge deviation is hardly sensitive to uniformity; with the gradient decrease, the uniformity of irrigators having the bigger exponent of flow form decreases gradually, but the uniformity of irrigators having the lesser exponent of flow form increases gradually, when the operating pressure of irrigators increases; when the lateral diameter increases, the uniformity improves generally, but sometimes it is likely to reduce under the downgrade condition; when the spacing between irrigator increase and the lateral length does not change, the uniformity will increase; with the lateral length increase, the uniformity decreases. According to the analysis of the eigenvalue and location of irrigator we can reach a conclusion that the eigenvalue has the close correlation with the gradient and exponent of flow form, while the location has only close relation to the gradient, but no relation to the exponent of flow form.The mathematical models of gravity and pumping tree pipe networks and the gravity and pumping pipe network of drip irrigation have been established, and the solution to genetic algorithms has been put forward. Taking the advantage of the linear programming and nonlinear prog...