Developing multi-objective optimization model with conflicting goals to improve the surge protection devices design for water hammer

In this study, a Multi-objective Optimization Model (MOM) is developed and solved for the optimum design of surge protection devices (including air chamber and shock damper) with conflicting goals. The shock damper is a new type of surge tank invented by researchers. For the first time, the design parameters of the shock damper as decision variables are raised in a MOM problem, and results are benchmarked with solving the model for the air chamber as well. Method of characteristics (MOC) is chosen for the numerical solution of water hammer PDE's and its system of equations for interior and boundary nodes are used as constraints of the optimization model. The conflicting criteria of the MOM are functions of safety in the system and installation cost of protection devices. In the following by using the weight coefficients and normalized objective functions obtained by dividing each of the mentioned functions by the maximum potential values of them, the resulting problem is solved by Genetic Algorithm (GA). The results, while investigated conceptually, show the significant improvement of multi-objective design in the performance and cost-saving in protection devices and the better function of shock damper regarding both criteria.