Optimal Design Of Sewer Networks

This paper focuses on optimal design for given layout of sewer networks. Because the best layout of a sewer system is usually tree-shaped, the theory of tree-shaped structure can be applied to sewer networks. Based on graph theory, 3-ary tree is put forward to be applied to sewer networks, so all the information of a specified sewer network can be translated into computer languages: a pipe is considered as a node of a tree, and all the information is stored in the node information. The mode of tree data structure can tell easily whether there are branches or not and the directions of the wastewater flows in the pipes.By studying all the methods of iterating binary trees, including pre-order, in-order, and post-order traversals, we find that post-order traversal is fit for sewer networks. So in this paper, the recursive algorithm of post-order traversal is applied to hydraulic calculation. Optimization can be finished by one calculation. Through the optimal calculation enumerating standard diameters is used to, which can speed up the calculation and save time.The mathematical models of sewer networks are discussed and built, including cost model and hydraulic model. This paper deals with the minimum cost including pipes cost and pumping station cost. The optimal design program is developed with Delphi language. The program has the characters of good visible interface, excellent man-machine conversation, better adaptability and so on.Finally, a case of a practical sewer network in Tianjin city is performed with this program. As the same way, this optimal design method can be applied to storm sewer networks.