Hydraulic simulation techniques for water distribution networks to treat pressure deficient conditions

Hydraulic analysis schemes for water distribution networks can be divided into demand-driven analysis (DDA) and pressuredriven analysis (PDA) according to the ways of calculating available outflow at nodes based on the assumption of nodal withdrawal estimation. Gradient algorithm-based numerical analysis schemes are generally used for these two types of hydraulic analysis. However, in abnormal conditions where hydraulic conditions rapidly change due to pipe damages or sudden increases in demands, the numerical solutions often derive unrealistic results that could lead to decision-making errors. In this study, the problems that may occur in hydraulic analysis of abnormal conditions were identified through sample cases using DDA and PDA models; then, the modification techniques resolving the simulation problems, the negative pressure in DDA and the total head reverse in PDA, were suggested. The proposed methods were verified by applying them to sample case study simulations. The application results reveal that the proposed approaches derive more realistic results under abnormal conditions, while the existing DDA and PDA tools produce unacceptable results, such as negative pressure and total head reverse occurrence. The scheme is further investigated for water network reliability evaluations and realistic ranges of demand supply under abnormal conditions were obtained.