Bong Seog Jung

Fluid transients and pipeline optimization using GA and PSO: the diameter connection

This paper describes the optimal selection of pipe diameters in a network considering steady state and transient analysis in water distribution systems. Two evolutionary approaches, namely genetic algorithms (GA) and particle swarm optimization (PSO), are used as optimization methods to obtain pipe diameters. Both optimization programs, inspired by natural evolution and adaptation, show excellent performance for solving moderately complex real-world problems which are highly nonlinear and demanding. The case study shows that the integration of GA or PSO with a transient analysis technique can improve the search for effective and economical hydraulic protection strategies. This study also shows that not only is the selection of pipe diameters crucially sensitive for the surge protection strategies but also that more global systematic approaches should be involved in water distribution system design, preferably at an early stage in the design process.

Multi-objective Design of Transient Network Models

The optimal design of a water distribution system under transient conditions is formulated as a two-objective optimization problem. The objectives are minimization of the total pipe costs and maximization of the hydraulic reliability for the transient network design model. Unlike most optimization models in which demands are set to their end-of-life levels, this approach assumes that the demand loadings vary throughout the design life of the system. Evolutionary algorithms are applied to support efficient search for Pareto optimal solutions to the dual-objective optimization problem. An example application is presented and relevant conclusions are stated.

A practical overview of unsteady pipe flow modeling: from physics to numerical solutions

Abstract Various unsteady or transient models have evolved in order to help engineers achieve economy of analysis, design, construction, operation and maintenance. The specific usage of each model is strongly dependent on the level of unsteadiness in the system and on the accuracy, assumptions and limitations of the applied mathematical model and its numerical solution. Although the research literature is quite clear on these issues, there is often much confusion in practice. In this paper, the key practical differences and advantage for the four transient models — water hammer models, rigid water column analysis, quasi-steady analysis and so-called Joukowski approach — are compared and contrasted with respect to three criteria: their physical attributes, the hydraulic predictions they lead to, and the related numerical considerations of stability and accuracy. A useful guideline for determining the degree of unsteadiness is presented and then linked to an appropriate unsteady model.