Improvement of the performance of NSGA-II and MOPSO algorithms in multi-objective optimization of urban water distribution networks based on modification of decision space

Abstract Water distribution networks require huge investment for construction. Involved people, especially researchers, are always seeking to find a way decreasing costs and achieving an efficient design. One of the main factors network design is selection proper diameters based on deficit flow pressure velocity in network. The reduction construction accomplished by minimizing diameter pipes which leads drop Supplying nodes one important principles, low will not provide complete water supply at consumption site. Therefore, this research, problem optimization several sample was defined with objectives cost minimization whole EPANET software used hydraulic analysis networks, multi-objective process performed coding NSGA-II MOPSO algorithms MATLAB environment linking them EPANET. function initially only considering relationship between length pipes, next definition, resulted violation allowable range added In both cases, schedule optimal answer executed. results showed that these have high ability solutions able optimize terms finding appropriate pipe diameter. time reaching convergence reduced limits significantly obtained small number repetitions. two-looped 20 30 iterations run 0.66 0.8 s, respectively, Lansey 150 250 5.7 9.5 were obtained.