The efficient management of hydraulic pressure in pipes is one of the main operational challenges in
water supply networks. This thesis considers pressure management that is actuated by pressure control
valves. The research investigates the problem of optimising valve locations and their operational
settings simultaneously - this approach is referred to as the design-for-control optimisation problem.
Initially, the thesis focuses on the minimisation of average zone pressure. The problem formulation
employs quadratic approximations of the non-smooth friction head loss formulae, and results in a
nonconvex mixed integer nonlinear program (MINLP).
Building upon previous work, the research studies two numerical schemes, namely penalty and relaxation
methods, for the solution of the formulated MINLP problem. While these methods are shown to
be effective on a published benchmark network model, their limitations for the solution of the problem
of optimal valve placement in large operational water networks are highlighted. A new problem
formulation is proposed, reducing the degree of nonlinearity within optimisation constraints. This
reformulation allows the application of outer approximation based schemes, enabling the solution of
the considered MINLP when large operational water supply networks are considered.
Since the MINLP for optimal valve placement is nonconvex, previously developed approaches do not
provide theoretical guarantees on the global optimality of the computed valve configurations. Here,
the research implements a branch and bound method to obtain certified bounds on the optimality
gap of the solutions. The branch and bound algorithm is shown to converge to good quality feasible
solutions, with bounds on the optimality gap comparable to the level of uncertainty inherent in water
network models.
Finally, the problem formulation for optimal valve placement is extended to the framework of multiobjective
optimisation, to evaluate the trade-offs between the minimisation of average zone pressure and
pressure variability. Scalarisation schemes are used to convert the original multiobjective MINLP into
series of single-objective MINLPs that are individually solved using outer approximation methods.
The proposed approaches have enabled the generation of wide and uniform Pareto fronts for a large
operational water network.