pressure driven simulation method

Hydraulic analysis methods of water distribution networks are divided into two types of demand driven simulation method (DDSM) and pressure driven simulation method (PDSM). In the DDSM analysis, it is assumed that nodal discharge is independent from nodal pressure and available discharge is always equal to demanded flow at consumption nodes. In PDSM analysis which results in much more realistic outputs than DDSM method, the assumption of nodal discharge independency from nodal pressure is rejected. In the recently proposed pressure-dependent relations, nodal discharge has been divided into two sections of volumetric and pressure-dependent discharges. In these relations, the exact contribution of volumetric and pressure-dependent discharges is not known and a portion of 50% has been considered for each of them. In the present study, by implementing field measurements, the portions of volumetric and pressure-dependent drinking water consumptions have been determined and the pressure-discharge relationship has been modified. Then, impact of the modification applied on pressure-discharge relationship on the output of PDSM model has been investigated. According to the obtained results, the considered portions for volumetric and pressure-dependent consumptions (50%) in previous pressure-discharge relations are inconsistent with reality. Using the modified pressure-discharge relation leads to increase in tank outlet discharge in the hydraulic model. Volumetric and pressure-dependent consumptions in cities like Oshnaviyeh can be considered approximately 13 and 87% of total drinking water consumption, respectively.

Water distribution networks (WDNs) are complicated infrastructures which their construction, operation and maintenance have considerable costs. Since most of the variables effective on the design and operation of WDNs cannot be computed and achieved accurately and definitely, uncertainty subject should be considered as an inseparable issue in the calculation of these networks. In this study, using the fuzzy logic concept and genetic optimization algorithm, the impact of uncertainties of input variables (nodal demands and pipe roughness coefficients) on the results of hydraulic analysis of two sample networks have been examined. In this regard, first, the fuzzy membership functions of input variables have been determined and by considering the simultaneous impacts of these variables' uncertainties, the output variables of hydraulic analysis have been calculated more accurately. Afterwards, variables of pressure, velocity and energy loss have been considered as representers for evaluating the hydraulic performance of network elements (nodal demand and pipes). In order to calculate the hydraulic performance indices of these elements, after analyzing the network based on the pressure driven simulation method, penalty curves defined according to the available standards, have been employed and the obtained results have been compared to the results of the demand driven simulation method. In addition, a new relation for combining the performance indices of network elements and obtaining an index for evaluating the total pipe performance and calculating the total hydraulic performance index of network has been introduced. According to the obtained results, slight uncertainties in the input variables of hydraulic analysis lead to high uncertainties in the outputs of the hydraulic analysis of WDNs. Meanwhile, velocity in pipes more than nodal pressures are affected by the uncertainties of input variables of hydraulic analysis. Also, implementing the pressure driven simulation method in performance evaluation of WDNs in their operation period leads to more reasonable and real results. For instance the total performance of network was 0.56 for 9-loop network and was 0.26 and 0.59 for 2-loop network, respectively, based on demand and pressure driven simulation methods.