Sewer networks comprise manholes connected by sewer pipes and other components, such as pumping stations and rising mains. These characteristics make it ideal for combination with a metaheuristic algorithm for optimal layout creation. The method is applied to two benchmark problems in the literature and shown to obtain near optimal hydraulic designs, while requiring very little computational effort. This paper focuses on the development of a computationally efficient heuristic optimisation algorithm by which, for a given layout, all constraints of the hydraulic design are systematically satisfied using slope information. Lejano (2006) found that, due to the complexity of simultaneous optimisation algorithms, most research has been done on the hydraulic optimisation sub-problem, while the layout remains static. However, the algorithms are computationally very expensive, since the optimisation procedure responsible for the hydraulic design has to be completed for a very large number of layout attempts. Simultaneous sewer network layout and hydraulic design optimisation using these algorithms has been investigated in recent times. Consequently the ability to improve sewer network designs through the use of metaheuristic optimisation algorithms could potentially yield a significant reduction in capital expenditure. Sewer networks form a vital part of public health in urban areas and constitute one of the most capital-intensive infrastructure investments (Wirhadikusumah et al 2001). Keywords : gravity sewer network, heuristic optimisation, hydraulic optimisation, contributor hydrograph, pipe size and slope Therefore it is ideally suited to be used in combination with a metaheuristic algorithm aimed at optimising the network layout. The method is used to solve two benchmark problems and is shown to obtain good solutions while being computationally extremely efficient. It makes use of required minimum slope information to heuristically determine optimal pipe sizes and slopes. This paper proposes a computationally efficient method for near optimal hydraulic design of a gravity sewer network. However, their computational complexity precludes their use in simultaneous layout and hydraulic optimisation, where a complete hydraulic optimisation has to be performed for each layout. Recently the use of metaheuristic algorithms, like Ant Colony Optimisation (ACO) for example, has gained popularity, and they perform well for a given static layout. This is a complex problem for which numerous solution approaches have been proposed. Hydraulic design optimisation is the task of determining suitable pipe diameters and slopes so as to minimise the installed cost of the network. N de Villiers G C van Rooyen M Middendorfįor a given sewer network layout and choice of pipe material, the total installed cost of the network is determined mainly by the pipe diameters and slopes.
Sewer network design: Heuristic algorithm for hydraulic optimisation
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