This study compares the numerical results obtained with an axisymmetric quasi two-dimensional (Q2D) model with those from two different types of dimensional models for smooth-turbulent transient flows generated by an instantaneous valve closure. The first is a high-accuracy three-dimensional computational fluid dynamics (3D-CFD) model. The second type is the one-dimensional (1D) model, analysing results from five unsteady friction formulations, namely four convolution integral-based (CIB) formulations and one instantaneous acceleration-based (IAB) formulation. The Q2D and 1D models are also compared with experimental data collected under laboratory conditions for a fast but non-instantaneous valve closure. The differences between the 1D, Q2D and 3D-CFD modelling approaches are quantified and discussed, focusing on the ability of each model to reproduce the different features of the transient flow phenomenon and the associated computation-accuracy trade-offs. The 3D-CFD model exhibits a more pronounced front-wave rounding, as it more accurately represents the valve conditions, where its closure induces highly turbulent flow with a strongly heterogeneous velocity profile. The Q2D model provides an accurate estimation of unsteady energy dissipation, when fully developed flow conditions are ensured with the advantage of requiring less computational effort than the 3D-CFD. These conclusions also apply to full convolution-based 1D models, whereas approximate 1D formulations can significantly reduce accuracy and limit their range of applicability. The comparison with experimental data corroborates the excellent results of the Q2D model. The Q2D model demonstrates to be an efficient alternative in terms of accuracy and computational time to 3D-CFD and 1D full convolution models.

The current paper primarily discusses the interconnection between water, energy and resilience, revisits the energy balance, proposes a modified calculation approach and metrics to assess system resilience criteria: energy efficiency and service flexibility. A sensitivity analysis is carried out considering: i) reference elevations, ii) levels of water losses, iii) contribution of shaft energy and pumping groups and iv) impact of water and energy efficiency improvement measures. The modified approach provides a realistic energy balance, while the original approach provides an ideal (no water losses) energy balance. Both approaches provide similar information for surrogate resilience metrics, but offer complementary information for the surplus energy index. Energy in excess per authorised consumption is most suitable to evaluate energy efficiency. Both the ratio between surplus energy and energy in excess and the surplus energy index are complementary in assessing service flexibility. Water and energy efficiency improvements should contribute to energy efficiency, ensuring service flexibility.

Abstract This paper presents a topology‐aware neural network approach for the detection, location, and quantification of abnormal consumptions in water distribution networks. The approach includes two main steps: the optimization of pressure sensor locations to maximize measurement sensitivity and the development of metamodels based on near real‐time data. The metamodel is designed and trained to predict the consumptions at all nodes based on pressure measurements and users' consumption collected by smart meters. These nodal consumptions deduced from the actual measured consumption allow the location of potential abnormal uses in the network. The proposed methodology enables the development of two metamodels, each tailored to specific applications based on the training data. The Static Metamodel relies on pressure head measurements under the assumption of constant nodal consumption, whereas the Dynamic Metamodel accounts for daily consumption variations, enabling the detection and location of abnormal consumption in real‐world scenarios. Both metamodels can detect the location of abnormal consumptions with reasonable accuracy, although this accuracy strongly depends on the number and spatial distribution of sensors, as well as the magnitude and location of the abnormal consumption. As water utilities implement advanced metering systems, the application of the proposed approach becomes more viable, enabling more effective and faster abnormal consumption detection.

This study aims to assess whether data acquisition frequency can affect the understanding of high-intensity precipitation events. Time series from a weighing gauge and a weighbridge gauge installed at the same site were analysed, with rainfall intensity data acquisition frequencies of 10 seconds and 5 minutes, respectively. To check the consistency of the data obtained by the two types of rainfall measuring instruments, a correlation analysis was carried out between the two time series.The results relating to acquisition frequency showed that, for an acquisition frequency of 5 minutes, there are significant losses of information (especially during heavy rainfall events) compared to acquisition frequencies of 10 seconds. The correlation analysis showed that the gauges are measuring correctly and that the data is accurate.

This paper proposes a new coefficient, a loop-diameter-uniformity coefficient (CLRI), to be integrated in the original Todini's resilience index for promoting the creation of hydraulic-loops in the optimal design problems of water distribution networks (WDN). This coefficient allows the definition of new surrogate resilience measures, such as the loop resilience index (LRI) and loop generalized resilience/failure index (LGRF), when using demand and pressure-driven analyses, respectively. The effectiveness of the coefficient in the uniformization of diameters in loops is demonstrated through the application to three WDN with distinct topologies and complexities. Two objectives are considered: capital costs minimization and hydraulic resilience maximization. The comparison of the optimal design solutions obtained when considering several resilience indices shows that those including the loop-diameter-uniformity coefficient effectively uniformize the diameters in the loops and least affect the original physical meaning of the index associated with surplus power. Optimization results obtained for demand and pressure-driven analysis are similar, as long as leakage volumes are low (ca. 10%) and the minimum pressure constraint is considered. The analysis of critical operational scenarios (pipe failure and firefighting) has shown that the proposed coefficient generally increases the overall resilience for both normal and abnormal operating conditions and, thus, should be used in WDN optimal design problems.

The paper proposes a novel methodology to locate and quantify entrapped air pockets created during pipe-filling events often found in intermittent water supply systems. Different filling conditions were tested in an experimental pipe with a high point. Measurements were taken and video recordings were carried out to assess air pocket volumes for different air release conditions at the downstream end of the pipe. The stochastic nature of air pocket creation resulted in varying air volumes. A new numerical model capable of simulating the air pocket creation, dragging and entrainment has been proposed. The new model, AirSWMM, was implemented as an extension of the Stormwater Management Model (SWMM) with stochasticity of air pocket formation reproduced by simulations with different air entrainment rates. The obtained numerical results show that the proposed model, even though based on a single-phase one-dimensional flow, can accurately locate and approximately quantify the entrapped air pocket volumes.

Water supply systems are vital infrastructures that provide an indispensable public service to society. An important percentage of water losses is caused by the development of cracks in water storage tanks, so efficient crack sealing repair works must be investigated. Biocementation has been used with good results for sealing cracks in many construction concrete infrastructures (e.g., buildings), as an alternative to standard materials, such as polymeric resins and cement mortars. This research aims at the experimental evaluation of biocimentation effectiveness in terms of watertightness for sealing cracks structures in contact with pressurized water, to be further applied to repair cracks in water storage tanks. Biocementation treatment is applied in cracks artificially created in small rectangular concrete plates 4 cm thick, with three crack widths (i.e., 0.1, 1 and 10 mm) to cover different real cases in which the repair with this technique is viable. The 10 mm width cracks were filled with sand before the treatment. Different rounds of bacteria Sporosarcina pasteurii are applied, being the efficiency of the treatment investigated by performing watertightness tests through variable water head tests starting at 10 kPa (1 m of water). Dissolution is discarded through measurements of ultrasonic pulse velocities before and after the watertightness tests and the results are explained by images of thermographic camera. The presence of biocement is confirmed by mineralogical analysis of the precipitate extracted from the cracks after breaking the plates through bending tests. Obtained results are very promising since the biocement precipitated can completely stop water flow in the 0.1 mm cracks and, for the cracks with 1 mm and 10 mm widths, the treatment can reduce the initial flow rate, on average, by 95% and 98%, respectively. The performance of the 10 mm width cracks previously filled with sand was similar to that of the 1 mm cracks, where no sand was used. The material strength recovered after the treatment is not as good as desirable: although a maximum recovery of 95.5% of the initial strength (average values) is found for the smallest crack width and it was almost null for the other two crack widths. These results demonstrate that the technique is effective when watertightness is required, but not when material strength must also be recovered. Further research is required to investigate the maximum water pressures that can be applied to each case, eventual effects of biocimentation on water quality and the durability of the treatment.

This paper presents and demonstrates a novel scenario-building methodology that integrates contextual and future time uncertainty into the performance assessment of water distribution networks (WDNs). A three-step approach is proposed: (i) System context analysis, identifying the main key factors that impact the WDN performance; (ii) Scenario definition, identifying the implicated WDN variables, describing its possible evolution, and conjugating them to further establish the reference scenario and the two most relevant and opposite ones; and (iii) Scenario modelling, simulating the WDN behaviour for those scenarios. The obtained spatial and temporal hydraulic results are further used to calculate performance metrics. The methodology is applied to a real WDN to assess resilience performance considering infrastructure asset robustness (real water loss performance indicator), service reliability (minimum pressure index), and service flexibility (network resilience index). A new formulation to assess the metric evolution over time is proposed, deducting the further-away performance results by using an uncertainty weight. The results demonstrate that the increase in metric amplitude for the opposite scenarios over time highlights future uncertainty, reflecting context uncertainty, and the comparison of metric spatial distribution (i.e., at the pipe/node levels) highlights critical areas with higher associated uncertainty.

This paper presents a novel model-based method for near real-time pipe burst location in water distribution networks by integrating measurement uncertainty into inverse analysis. The method accounts for expected errors between measured and computed values, providing a pipe burst location area whose size varies according to the expected error level and the burst size. The proposed method is demonstrated and compared with the traditional inverse approach using a real case study with artificial bursts of different sizes and with different pressure signal noise levels. The performance of both methods is also assessed and discussed considering the effect of seasonal water demands. The traditional inverse analysis fails to accurately locate the pipe burst events, and depending on the expected error level and pipe burst size, the obtained locations may be significantly further away from the real burst location. Conversely, the proposed method does not point to the exact burst location but provides an approximated area in which step-testing can be carried out to pinpoint the exact burst location; the size of this area can be larger or smaller depending on the burst flow rate and signal uncertainty.

Pipe networks exhibit complex geometries and are equipped with electromechanical devices capable of generating hydraulic transients. Most of these devices are remotely controlled and managed through an integrated system that prioritizes network demands. This implies that potential hazardous pressure peaks, that may occur during each operation, may need to be taken into account. Consequently, when multiple operations take place in a short time interval, transient pressure waves, generated in different parts of the network and traveling back and forward, overlap and can be larger than the design maximum pressure. To address this concern, it is essential to evaluate the pressure-damping rate of critical maneuvers and to identify a “safe” time interval between maneuvers to prevent the risk of inappropriate pressure waves overlapping. With the aim of analyzing the damping rate of closure maneuvers, both numerical and laboratory experiments have been executed for a laminar flow in a reservoir-pipe-valve system. In this context, a three-dimensional computational fluid dynamics, a one-dimensional and global model, the latter based on a sinusoidal function, have been used. Guidelines are then presented for identifying the safe time interval between maneuvers.

This research aims to present relevant developments carried out in the domains of energy recovery and the associated digital technology in the water sector. These include the implementation of digital twins of a PRV and energy converters. Several performance tests have been carried out in pumps operating as turbines (PATs) when replacing pressure-reducing valves (PRVs) or coupled to them. Based on virtual prototype of turbines, the numerical modelling of a PRV and tested PATs, with radial and axial impellers, have been developed. On the other hand, Digital Twins (DTs) provide useful data collection/analysis tools for reproducing disruption scenarios for resilience assessment purposes and analyzing asset prognosis and the system efficiency to determine proactive management models.

Intermittent water supply systems are prone to air entrapments during the pipe filling phase. This work aims to analyse and discuss the numerical results obtained by applying the recently developed AirSWMM model, an extension of SWMM incorporating air phase, to a laboratory network. Experimental data consisting of pressure-head at multiple locations and video recordings of air entrapments are collected in a single loop network with a high point, for different pipe-filling conditions, system layouts and node elevations. Experimental tests have shown that the air entrapment occurred not only at the high point but also throughout the pipe network, creating air pockets with elongated shapes and larger volumes than for single pipes. AirSWWM model with air-entrapment formation, growth and transport is tested in the pipe network, and results are compared with measurements. AirSWWM model can correctly locate large air pockets but underestimates their volume.

In-line valves are devices typically used for isolation or flow regulation in pipe systems, playing a key role in the operational management of transmission mains (TM). However, there is no fast and expeditious procedure available for checking the efficacy of the sealing mechanism, and its ability to prevent leakage, unwanted flow or partial blockages, which is a crucial action for any maintenance operation. Due to the different values of the conveyed discharge, the diameter changes along the TM at a series junctions which therefore makes diameter changes a very common singularity. This paper has two aims. The first one is to evaluate the feasibility of Inverse Transient Analysis (ITA) for checking the sealing of in-line valves. In particular, the primary objective of the numerical model is to identify the distinctive features of the measured pressure signals that correspond to the status of an in-line valve, discerning whether it is fully sealed or partially closed. The second objective is to use Direct Analysis (DA) of the pressure signals to appropriately capture the transient response of the series junctions. To address these issues, safe transients have been generated in a real TM by means of a Portable Pressure Wave Maker (PPWM) device, refined at the Water Engineering Laboratory (WEL) of the University of Perugia, Italy. The results of the field tests and numerical model point out that the positive pressure wave reflected by the in-line valve is smaller than the one expected if it were perfectly sealed. Moreover, the transient response of the series junction has been properly captured by the DA of the pressure signal. Accordingly, the proposed procedures have been demonstrated to be suitable tools for the management of long transmission pipelines.

Understanding the interaction between pressure waves and partial blockages in pipe systems is crucial for enhancing noninvasive detection methods based on the execution of transient tests. Although laboratory and one-dimensional numerical models have also provided valuable results from the practical point of view, analyzing the transient response of partial blockages in terms of local flow field characteristics is of great interest. This paper examines the transient response in laminar flow conditions of partial blockages by using a Computational Fluid Dynamics model. In particular, the time history of pressure and local velocity of transient events is examined during the early phase characterized by the first pressure wave reflected by the partial blockage. Laminar conditions are chosen for their minimal risk in real pipe systems as they give rise to small overpressures. The behavior of discrete partial blockages at two locations is analyzed in detail, with a pipe with no blockage scenario as a reference. Simulations of discrete partial blockages with different severity confirm that the reflected pressure wave contains enough information for locating and characterizing partial blockages. The obtained results provide critical insights for the organization of transient tests toward the detection of partial blockages.

This study presents insights into how existing faults in pipe systems, like leaks and air pockets, modify transient pressure waves in terms of shape, damping, and phase shift, based on experimental tests conducted at the Hydraulics Laboratory of the Instituto Superior Técnico. Leaks have a major effect on pressure wave damping and shape that increases with the leak size; however, they also preserve the wave phase. The air pocket effect strongly depends on the air pocket size and location, tending to increase wave damping and delay. Also, there is an air pocket volume that leads to the maximum pressures being higher than Joukowsky’s overpressure.