用两级优化法进行喷微灌配水支管设计

采用两级优化设计模型进行喷微灌支管设计，第一级优化采用拉格朗日法求解非线性规划模型，以年费用最低为目标函数，以连续管径为决策变量，获得一组最优管径组合。第二级采用枚举法进行优化设计，在第一次连续管径基础上，按照施工要求的变径数，选择出靠近连续管径的几个商用管径，以年费用最低为目标函数，以管径和管长作为决策变量，获得最优管径和管长组合，最后计算出各节点的水压力。该方法不仅使年费用最低，而且满足了施工要求，可直接用于喷微灌支管的施工设计。

Two grades optimal design of submain manifold for sprinkle irrigation

The two grades optimal design method is applied to design the submain manifold for sprinkle (or micro) irrigation. In the first grade optimization, the Lagrange method is adopted to solve the nonlinear programming model. The annual expense is used as the objective function and the successive tube diameter is set as the decision variation. Then, a series of optimal diameters are obtained. In the second grade, the enumeration approach is applied. On the basis of the first optimized successive diameters, some diameters available in market are selected according to the number of diameters variation for operational requirement. After that, the minimum annual expense is set as the objective function and tube diameter and length are used as the decision variation to obtain the optimal combination of diameter and length. The water pressure head at every node along the manifold can be calculated consequently.