Publications
92 results found
Jara-Arriagada C, Ulusoy A-J, Stoianov I, 2024, Localization of transient pressure sources in water supply networks with connectivity uncertainty, Journal of Water Resources Planning and Management, Vol: 150, ISSN: 0733-9496
The localization of sources of pressure transients is essential for proactively managing and reducing the adverse effects of these transients in water supply networks (WSNs). This paper addresses the issue of localizing transient sources in a WSN where there is uncertainty about the network connectivity. If closed valves or blockages in the pipes are not accounted for, it can result in inaccurate knowledge of the network connectivity, leading to incorrect estimations about the sources of pressure transients. The problem is challenging due to the added uncertainties in estimating the velocity of pressure waves and determining their arrival times at pressure monitoring sites. In order to systematically investigate this problem, the paper presents a novel theoretical framework for localizing the source of pressure transients in WSNs with uncertain connectivity. The problem is formulated as a mixed-integer quadratic program, which consists of minimizing the difference between analytical and measured pressure wave arrival times for multiple pairs of time-synchronized sensors. Unlike previous approaches, the k-shortest path (with respect to time) routing problem is incorporated into the problem formulation to account for multiple potential wave propagation paths. The optimization problem is then solved using an off-the-shelf solver, and a methodology is developed to ensure the reliability of the optimization approach. We apply the proposed methodology to numerically simulated pressure transient data for a benchmark WSN and compare it against a previously published method. The results show a notable improvement in accurately localizing the source of a transient in the presence of unknown closed valves or pipe blockages. Provided pressure wave speeds are predetermined, the proposed methodology is able to simultaneously localize the source of a pressure transient and validate the assumed hydraulic connectivity of a WSN. In this way, any irregularities or uncertainties in net
Jara-Arriagada C, Stoianov I, 2024, Pressure-induced fatigue failures in cast iron water supply pipes, Engineering Failure Analysis, Vol: 155, ISSN: 1350-6307
Cast iron pipes have been extensively utilised in water supply networks worldwide. Many of these pipes are either at the onset or within their wear-out phase, during which failure rates rapidly increase, and the pipes should be repaired or replaced. However, the replacement and rehabilitation of these pipes might require extensive resources and time. Therefore, it is essential to investigate the effects of operational practices that might reduce failure rates for ageing cast iron pipes. In this paper, we investigate the conditions under which water pressure fluctuations may impact and accelerate fatigue failures in cast iron pipes. We carried out a systematic review of the mechanical properties of cast iron pipes and conducted sensitivity analyses to estimate fatigue crack propagation using fracture mechanics. Our investigation suggests that cast iron pipes which are affected by reduced wall thickness due to corrosion may experience a significant decrease in their operational life when subjected to water pressure fluctuations. Moreover, this negative influence of pressure fluctuations is exacerbated with an increase in the mean operating pressure. As an example, a 150 mm pipe featuring a corrosion patch of about 7 mm depth could extend its remaining fatigue life by over fourfold through a minor reduction of both mean pressure and pressure fluctuations of approximately 10 m H₂O each. The manuscript further explores various pressure reduction combinations and trends, demonstrating the beneficial effects of reducing both mean pressure and pressure fluctuations. Consequently, the presented analysis suggests that water operators should proactively manage (reduce) the magnitude of both pressure components to extend the operating life of ageing cast iron pipes.
Konstantinou C, Jara-Arriagada C, Stoianov I, 2024, Investigating the impact of cumulative pressure-induced stress on machine learning models for pipe breaks, Water Resources Management, Vol: 38, Pages: 603-619, ISSN: 0920-4741
Significant financial resources are needed for the maintenance and rehabilitation of water supply networks (WSNs) to prevent pipe breaks. The causes and mechanisms for pipe breaks vary between different WSNs. However, it is commonly acknowledged that the operational management and water pressure influence significantly the frequency of pipe breaks. Pipe breaks occur when the water pressure exceeds the tensile strength of a pipe, or due to repetitive pressure cycles that result in fatigue-related failures. Considering these pipe failure modes, a new metric known as cumulative pressure-induced stress has been introduced. This metric takes into account both static and dynamic pressure components that contribute to pipe breaks, including mean pressure and the magnitude and frequency of pressure fluctuations, respectively. The impact of CPIS on pipe breaks has not been extensively investigated. Consequently, this study investigates and evaluates the impact of this metric when incorporated as an explanatory variable in Random Forest (RF) models that analyse the key causes of pipe breaks in two WSNs. Different RF models were developed both with and without incorporating pressure components. Subsequently, the performance of these models and the significance of each input variable were assessed. The results of this study suggest that CPIS is an important variable, especially in cases where pressure-related factors play a significant role in pipe breaks. Consequently, incorporating CPIS has shown a notable improvement in the accuracy of pipe break models.
Ulusoy AJ, Nerantzis D, Stoianov I, 2023, Adaptive MPC for Burst Incident Management in Water Distribution Networks, IEEE Transactions on Control of Network Systems, Vol: 10, Pages: 2060-2071
This article investigates an adaptive control strategy which takes advantage of remotely actuated pumps and valves to improve the performance of water distribution networks (WDN) during burst incidents. The proposed strategy relies on a model predictive control to switch between problem formulations corresponding to normal operating conditions and burst conditions. The optimal control problems are formulated as nonconvex nonlinear programs, where the action of fixed-speed pumps and control valves (nonreturn and bidirectional) is modeled exactly and burst remedial interventions are represented using time-dependent connectivity matrices. We propose an efficient solution method based on reformulations and approximations of the nonconvex objectives and constraints and apply the proposed strategy to the adaptive control of an operational WDN during a burst incident. The numerical experiments show that the computed burst control settings allow to partially or completely restore customer supply following the detection of a burst while maintaining minimum water levels in the network tanks and without increasing the cost of pumping operations. The results suggest that the proposed adaptive control strategy can be implemented alone, to mitigate the impact of bursts incidents in WDNs at minimum cost, or to complement traditional remedial interventions.
Jenks B, Pecci F, Stoianov I, 2023, Convex heuristics for optimising the self-cleaning capacity of water distribution networks, 19th Computing and Control in the Water Industry (CCWI) Conference, Leicester, United Kingdom, 04-07 September 2023
Pecci F, Stoianov I, 2023, Bounds and convex heuristics for bi-objective optimal experiment design in water networks, COMPUTERS & OPERATIONS RESEARCH, Vol: 153, ISSN: 0305-0548
Jenks B, Pecci F, Stoianov I, 2023, Optimal design-for-control of self-cleaning water distribution networks using a convex multi-start algorithm, WATER RESEARCH, Vol: 231, ISSN: 0043-1354
- Author Web Link
- Cite
- Citations: 2
Nerantzis D, Stoianov I, 2023, Optimization-based selection of hydrants and valves control in water distribution networks for fire incidents management, IEEE Systems Journal, Vol: 17, Pages: 134-145, ISSN: 1932-8184
In England and Wales, water utilities reduce hydraulic pressure to a minimum regulatory threshold in order to reduce leakage and avoid financial penalties. However, utilities are not legally bound to guarantee specific flow rates from fire hydrants, thus posing a risk for firefighting. We formulate a biobjective mixed-integer nonlinear program (MINLP) to simultaneously determine control valve settings and the location of fire hydrants to be utilized in a water distribution network during urban fire incidents. The goal is to provide the required flow rate from the fire hydrants while minimizing 1) the distance of the utilized fire hydrants from the fire location and 2) the impact on customer supply. As the solution is required in real-time, we propose an optimization-based heuristic, which relies on iteratively solving a NLP approximation and relaxation of the MINLP formulation. Furthermore, we assess the quality of the heuristic solutions for the presented study case by calculating global optimality bounds. The proposed heuristic is applied to an operational water distribution network.
Waldron A, Ulusoy A-J, Pecci F, et al., 2022, Principal Component Based Sampling for the Continuous Maintenance of Hydraulic Models, WATER RESEARCH, Vol: 222, ISSN: 0043-1354
- Author Web Link
- Cite
- Citations: 2
Ulusoy A-J, Mahmoud HA, Pecci F, et al., 2022, Bi-objective design-for-control for improving the pressure management and resilience of water distribution networks., Water Research, Vol: 222, Pages: 118914-118914, ISSN: 0043-1354
This paper investigates control and design-for-control strategies to improve the resilience of sectorized water distribution networks (WDN), while minimizing pressure induced pipe stress and leakage. Both evolutionary algorithms (EA) and gradient-based mathematical optimization approaches are investigated for the solution of the resulting large-scale non-linear (NLP) and bi-objective mixed-integer non-linear programs (BOMINLP). While EAs have been successfully applied to solve discrete network design problems for large-scale WDNs, gradient-based mathematical optimization methods are more computationally efficient when dealing with large search spaces associated with continuous variables in optimal network control problems. Considering the advantages of each method, we propose a sequential hybrid method for the optimal design-for-control of large-scale WDNs, where a refinement stage relying on gradient-based mathematical optimization is used to solve continuous optimal control problems corresponding to design solutions returned by an initial EA search. The proposed method is applied to compute the Pareto front of a bi-objective design-for-control problem for the operational network BWPnet, where we consider reopening closed connections between isolated supply areas. The results show that the considered design-for-control strategy increases the resilience of BWPnet while minimizing pressure induced leakage. Moreover, the refinement stage of the proposed hybrid method efficiently improves the coarse approximation computed by the initial EA search, returning a continuous and even Pareto front approximation.
Pecci F, Stoianov I, Ostfeld A, 2022, Optimal Design-for-Control of Water Distribution Networks via Convex Relaxation, 2nd WDSA/CCWI Joint Conference, Publisher: Editorial Universitat Politècnica de València
<jats:p>This paper considers joint design-for-control problems in water distribution networks (WDNs), where locations and operational settings of control actuators are simultaneously optimized. We study two classes of optimal design-for-control problems, with the objectives of controlling pressure and managing drinking-water quality. First, we formulate the problem of optimal placement and operation of valves in water networks with the objective of minimizing average zone pressure, while satisfying minimum service requirements. The resulting mixed-integer non-linear optimization problem includes binary variables representing the unknown valve locations, and continuous variables modelling the valves’ operational settings. In addition, water utilities aim to maintain optimal target chlorine concentrations, sufficient to prevent microbial contamination, without affecting water taste and odour, or causing growth of disinfectant by-products. We consider the problem of optimal placement and operation of chlorine booster stations, which reapply disinfectant at selected locations within WDNs. The objective is to minimize deviations from target chlorine concentrations, while satisfying lower and upper bounds on the levels of chlorine residuals. The problem formulation includes discretized linear PDEs modelling advective transport of chlorine concentrations along network pipes. Moreover, binary variables model the placement of chlorine boosters, while continuous variables include the boosters’ operational settings. Computing an exact solution for the considered mixed-integer optimization problems can be computationally impractical when large water network models are considered. We investigate scalable heuristic methods to enable the solution of optimal design-for-control problems in large WDNs. As a first step, we solve a convex relaxation of the considered mixed-integer optimization problem. Then, starting from the relaxed solution, we implement randomizat
Jara-Arriagada C, Stoianov I, 2022, High resolution water pressure monitoring for the assessment of fatigue damage in water distribution pipes, 2nd WDSA/CCWI Joint Conference, Publisher: Editorial Universitat Politècnica de València
<jats:p>In the last decade, the increasing implementation of high frequency monitoring has shown that water distribution networks are frequently affected by pressure transients. In some instances, even thousands of cyclic loadings can be exerted on pipes posing a risk of fatigue damage. High frequency monitoring, which can be as high as 128 samples per second, allows the capturing of extremely rapid transient events, otherwise undetectable using normal 15 min telemetry monitoring. Thus, providing a precise picture and awareness of the full dynamic activity in a pipe. However, despite this new awareness of a possible fatigue risk on pipes, current research has not be able to show to the extent of the relevance of this risk. Main limiting factors of previous published research have been short high frequency monitoring periods, limiting the generalisation of previous findings, and few mechanistic analysis utilising measured data. To address these issues, this work presents the analysis and evaluation of several months to years of high frequency monitoring water pressure data at various locations in operating water distribution networks. We have obtained extensive time series datasets with highly detailed information of transient events, and utilised this information together with knowledge of fracture mechanics to assess the extent of fatigue damage on pipes. In order to perform the analyses, our time series data were converted into tuples of number of cycles and magnitude by utilising a rainflow cycle counting algorithm. This algorithm allows the counting of full cyclic loadings and their magnitude in an spectral loading history. Such information can then be utilised for fatigue analysis. In particular, we have used theory of fatigue crack propagation to assess number of cycles to failure. Results from this research suggest evidence that at some logging locations, and depending on the pipe material, and current deterioration state, fatigue damage due constant cy
Stoianov I, Pecci F, Ulusoy A-J, 2022, Water Supply Networks with Dynamically Adaptive Connectivity and Hydraulic Conditions:&#160;Design and Control
<jats:p>&lt;p&gt;Water utilities around the globe are facing an extraordinary demand for the secure supply of potable water as a result of population growth, urbanisation and climate change. New knowledge, technologies and systems-based approaches are urgently needed to adaptively optimise resource capacity, operations and assets utilisation during a time of escalating environmental, regulatory and financial pressures.&lt;br&gt;This presentation summarises fundamental mathematical and engineering challenges for the design, optimisation and control of next generation water supply networks. These networks dynamically change connectivity (topology), hydraulic conditions and operational objectives. The design and control of dynamically adaptive water supply networks aims to improve pressure management, resilience, efficiency, incident management and sustainability.&lt;br&gt;The current ability of complex water networks to dynamically adapt their connectivity, operational conditions and application objectives is extremely limited. Water supply networks are operated as disjointed (or loosely coupled) sub-systems that have evolved over many years. The operational practice of sub-dividing water supply networks into small discrete areas, District Metered Areas (DMAs), has been successfully implemented by the UK water industry to reduce leakage in excess of 30% in the last 25 years. A DMA has a fixed network topology with permanent boundaries, typically a single inlet and it includes between 1,000 and 3,000 customer connections. By closing boundary valves to form small metered areas, the natural redundancy of connectivity and supply within large looped networks is severely reduced; thus affecting operational resilience, water quality and energy losses. Consequently, the implementation of DMAs has introduced operational constraints that affect both consumers and utilities. Furthermore, these constraints are beginning to inf
Ulusoy A-J, Pecci F, Stoianov I, 2022, Bi-objective design-for-control of water distribution networks with global bounds, Optimization and Engineering, Vol: 23, Pages: 527-577, ISSN: 1389-4420
This manuscript investigates the design-for-control (DfC) problem of minimizing pressure induced leakage and maximizing resilience in existing water distribution networks. The problem consists in simultaneously selecting locations for the installation of new valves and/or pipes, and optimizing valve control settings. This results in a challenging optimization problem belonging to the class of non-convex bi-objective mixed-integer non-linear programs (BOMINLP). In this manuscript, we propose and investigate a method to approximate the non-dominated set of the DfC problem with guarantees of global non-dominance. The BOMINLP is first scalarized using the method of ϵ-constraints. Feasible solutions with global optimality bounds are then computed for the resulting sequence of single-objective mixed-integer non-linear programs, using a tailored spatial branch-and-bound (sBB) method. In particular, we propose an equivalent reformulation of the non-linear resilience objective function to enable the computation of global optimality bounds. We show that our approach returns a set of potentially non-dominated solutions along with guarantees of their non-dominance in the form of a superset of the true non-dominated set of the BOMINLP. Finally, we evaluate the method on two case study networks and show that the tailored sBB method outperforms state-of-the-art global optimization solvers.
Pecci F, Stoianov I, Ostfeld A, 2022, Convex heuristics for optimal placement and operation of valves and chlorine boosters in water networks, Journal of Water Resources Planning and Management, Vol: 148, ISSN: 0733-9496
This paper investigates the problem of optimal placement and operation of valves and chlorine boosters in water networks. The objective is to minimize average zone pressure while penalizing deviations from target chlorine concentrations. The problem formulation includes non-convex quadratic terms within constraints representing energy conservation law for each pipe, and discretized differential equations modelling advective transport of chlorine concentrations. Moreover, binary variables model the placement of valves and chlorine boosters. The resulting optimization problem is a non-convex mixed integer non-linear program, which is difficult to solve, especially when large water networks are considered. We develop a new convex heuristic to optimally place and operate valves and chlorine boosters in water networks, while estimating the optimality gaps for the computed solutions. We evaluate the proposed heuristic using case studies with varying sizes, and levels of connectivity and complexity including two large operational water networks. The convex heuristic is shown to generate good quality feasible solutions in all problem instances with bounds on the optimality gap comparable to the level of uncertainty inherent in hydraulic and water quality models.
Pecci F, Stoianov I, Ostfeld A, 2022, Optimal Design-for-Control of Chlorine Booster Systems in Water Networks via Convex Optimization, Pages: 1988-1993
In this manuscript, we investigate the design-for-control problem to optimize locations and operational settings of chlorine boosters in water networks. The objective is to minimize deviations from target chlorine concentrations. The problem formulation includes discretized linear PDEs modeling advective transport of chlorine concentrations. Moreover, binary variables model the placement of chlorine boosters. The resulting optimization problem is a convex mixed integer program (MIP), which is difficult to solve, especially when large water networks are considered. We develop a new swapping heuristic to optimally place and control chlorine boosters in water networks. The proposed method relies on a continuous relaxation of the original MIP. We evaluate the heuristic using two case studies, including one large operational water network from the UK.
Nerantzis D, Stoianov I, 2021, Adaptive Model Predictive Control for fire incidents in water distribution networks, Journal of Water Resources Planning and Management, Vol: 148, Pages: 1-15, ISSN: 0733-9496
Water utilities in UK aim in network pressure reduction as a means to reduce leakage, in order to meet regulatory targets and avoid financial penalties. At the same time, however, they are not legally bound to guaranty specific fire flow rates at fire hydrants, thus posing a potential a risk to fire fighting. In the exiting literature, fire-flows in water distribution networks have been considered primarily with respect to design, vulnerability and capacity analysis, while control of pumps and valves has focused mainly on minimizing energy costs (and to a lesser extent pressure) under normal operating conditions. This study presents a (non-linear) adaptive model predictive control methodology, for water distribution networks, combining two separate modes of control: 1) Normal Control, when the network operates under normal conditions and the objective is to minimize energy costs and average zonal pressure. 2) Fire Control, when a fire incident occurs and fire-flows need to be delivered at hydrant nodes while, to the furthest possible extent, resume delivery of customer demand without over pressuring the network. The proposed methodology is applied on an operational network from UK.
Pecci F, Stoianov I, Ostfeld A, 2021, Relax-tighten-round algorithm for optimal placement and control of valves and chlorine boosters in water networks, European Journal of Operational Research, Vol: 295, Pages: 690-698, ISSN: 0377-2217
In this paper, a new mixed integer nonlinear programming formulation is proposed for optimally placing and operating pressure reducing valves and chlorine booster stations in water distribution networks. The objective is the minimization of average zone pressure, while penalizing deviations from a target chlorine concentration. We propose a relax-tighten-round algorithm based on tightened polyhedral relaxations and a rounding scheme to compute feasible solutions, with bounds on their optimality gaps. This is because off-the-shelf global optimization solvers failed to compute feasible solutions for the considered non-convex mixed integer nonlinear program. The implemented algorithm is evaluated using three benchmarking water networks, and they are shown to outperform off-the-shelf solvers, for these case studies. The proposed heuristic has enabled the computation of good quality feasible solutions in most instances, with bounds on the optimality gaps that are comparable to the order of uncertainty observed in operational water network models.
Waldron A, Pecci F, Stoianov I, 2021, Closure to "Regularization of an Inverse Problem for Parameter Estimation in Water Distribution Systems" by Alexander Waldron, Filippo Pecci, and Ivan Stoianov, JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT, Vol: 147, ISSN: 0733-9496
- Author Web Link
- Cite
- Citations: 2
Blocher C, Pecci F, Stoianov I, 2021, Prior assumptions for leak localisation in water distribution networks with uncertainties, Water Resources Management, Vol: 35, Pages: 5105-5118, ISSN: 0920-4741
Hydraulic model-based leak (burst) localisation in water distribution networks is a challenging problem due to a limited number of hydraulic measurements, a wide range of leak properties, and model and data uncertainties. In this study, prior assumptions are investigated to improve the leak localisation in the presence of uncertainties. For example, ℓ2-regularisation relies on the assumption that the Euclidean norm of the leak coefficient vector should be minimised. This approach is compared with a method based on the sensitivity matrix, which assumes the existence of only a single leak. The results show that while the sensitivity matrix method often yields a better leak location estimate in single leak scenarios, the ℓ2-regularisation successfully identifies a search area for pinpointing the accurate leak location. Furthermore, it is shown that the additional error introduced by a quadratic approximation of the Hazen-Williams formula for the solution of the localisation problem is negligible given the uncertainties in Hazen-Williams resistance coefficients in operational water network models.
Jara-Arriagada C, Stoianov I, 2021, Pipe breaks and estimating the impact of pressure control in water supply networks, Reliability Engineering & System Safety, Vol: 210, Pages: 1-11, ISSN: 0951-8320
The deterioration and fracture of water supply pipes present a major threat for the continuous provision of drinking water. The hydraulic pressure in pipes is an influential factor for the occurrence of pipe breaks. However, little evidence has been provided so far for the quantitative assessment of the impact of pressure control on reducing the number of pipe breaks. In this paper, we applied logistic regression with polynomial terms, and a sensitivity analysis to assess the potential impact of pressure control on reducing pipe breaks. A large dataset of historic pipe breaks was used to develop and validate the presented method. Cast iron and asbestos cement pipes were examined in detail. Results showed that pipe breaks could be decreased by 18% to 30% by reducing the mean pressure for the investigated cohorts of asbestos cement and cast iron pipes. Pressure range reduction could provide larger impacts on both pipe materials. These results indicate that proactively controlling the hydraulic pressure may have a potentially significant impact on the reliability and sustainability of water supply networks.
Mijic A, Whyte J, Fisk D, et al., 2021, The Centre for Systems Engineering and Innovation – 2030 vision and 10-year celebration
The 2030 vision of the Centre is to bring Systems Engineering and Innovation to Civil Infrastructure by changing how cross-sector infrastructure challenges are addressedin an integrated way using principles of systems engineering to maximise resilience, safety and sustainability in an increasingly complex world.We want to better understand the environmental and societal impacts of infrastructure interventions under uncertainty. This requires a change in current approaches to infrastructure systems engineering: starting from the natural environmentand its resources, encompassing societaluse of infrastructure and the supporting infrastructure assets and services.We argue for modelling that brings natural as well as built environments within the system boundaries to better understand infrastructure and to better assess sustainability. We seethe work as relevant to both the academic community and to a wide range of industry and policy applications that are working on infrastructure transition pathways towards fair, safe and sustainable society.This vision was developed through discussions between academics in preparation for the Centre for Systems Engineering and Innovation (CSEI) 10 years celebration. These rich discussions about the future of the Centre were inspired by developing themes for a celebration event, through which we have summarised the first 10 years of the Centre’s work and our vision for the future and identified six emerging research areas.
Ulusoy A-J, Pecci F, Stoianov I, 2020, A MINLP-based approach for the design-for-control of resilient water supply systems, IEEE Systems Journal, Vol: 14, Pages: 4579-4590, ISSN: 1932-8184
The improvement in resilience of water supplysystems by increasing their redundancy, either in energyor in connectivity, is a common priority when doing rehabilitation and expansion. This however can come at thecost of other aspects of network performance, such asleakage management. In this work, we consider the designfor-control problem of adding new connections (from a predefined set of candidate pipes) to water supply systems toimprove their resilience to failure events while minimizingthe impact on leakage management under normal operatingconditions. We present a mixed-integer non-linear programming formulation of the problem of optimal link additionfor the minimization of average zone pressure, a surrogatemeasure of pressure dependent leakage. We implement amethod based on spatial branch-and-bound to solve theproblem on a case study network from the literature andan operational network part of an urban water system inthe UK. Finally, we validate the improvement in networkresilience resulting from the addition of new connectionsby performing an a posteriori critical link analysis, usingthe hydraulic resilience measure of reserve capacity.
Konstantinou C, Stoianov I, 2020, A comparative study of statistical and machine learning methods to infer causes of pipe breaks in water supply networks, URBAN WATER JOURNAL, Vol: 17, Pages: 534-548, ISSN: 1573-062X
Water supply pipes age, deteriorate and break, which puts at risk the continuous provision of safe potable water endangering the public health in cities. Risk management methods are increasingly applied to optimise the capital investment for pipe replacement and rehabilitation, taking into account the probability and hydraulic impact of pipe breaks. As part of this process, however, historic pipe break data and statistical methods should be utilised to gather causal insights for past breaks to inform operational changes and/or capital investment decisions in order to reduce future breaks. This paper presents a comparative study of statistical and machine learning methods to carry out an exploratory causal analysis for historic pipe breaks in an operational water supply network. Regression models for count data and probabilistic models have been developed. The performance of these models was assessed and enhanced with the introduction of interactions and the inclusion of different network representations.
Pecci F, Parpas P, Stoianov I, 2020, Sequential convex optimization for detecting and locating blockages in water distribution networks, Journal of Water Resources Planning and Management, Vol: 146, ISSN: 0733-9496
Unreported partially/fully closed valves or other type of pipe blockages in water distribution networks result in unexpected energy losses within the systems, which we also refer to as faults. We investigate the problem of detection and localization of such faults. We propose a novel optimization-based method, which relies on the solution of a non-linear inverse problem with l1 regularization. We develop a sequential convex optimization algorithm to solve the resulting non-smooth non-convex optimization problem. The proposed algorithm enables the use of non-smooth terms within the problem formulation, and exploits the sparse structure inherent in water network models. The performance of the developed method is numerically evaluated to detect and localize blockages in a large water distribution network using both simulated and experimental data. In all experiments, the sequential convex optimization algorithm converged in less than three seconds, suggesting that the proposed fault detection and localization method is suitable for near real-time implementation. Furthermore, we experimentally validate the developed method for near real-time fault diagnosis in a large operational water network from the UK. The method is shown to successfully detect and localize blockages, with real system modelling uncertainties.
Waldron A, Pecci F, Stoianov I, 2020, Regularisation of an inverse problem for parameter estimation in water distribution networks, Journal of Water Resources Planning and Management, Vol: 146, ISSN: 0733-9496
An accurate hydraulic model of a water distribution network (WDN) is a critical prerequisite for a multitude of operational, optimisation and planning tasks. The accuracy of a hydraulic model can only be maintained through its periodic calibration and validation with acquired pressure and flow data from a WDN. It is important that this process is robust and computationally efficient. This paper describes the regularisation of an inverse problem to deal with data uncertainties and ill-posedness of parameter estimation problems in WDNs. A novel data driven strategy is presented for tuning the regularisation hyper-parameter for the inverse problem and also for validating the results on an independent set of operational hydraulic data. A limited-memory quasi-Newton method (L-BFGS19 B) is implemented for solving the resulting regularised nonlinear inverse problem. Furthermore, the implemented method utilises either the Darcy-Weisbach or Hazen-Williams head loss formulae, and is investigated both with and without pipe grouping. An extensive experimental programmewas carried out to acquire unique hydraulic data from an operational WDN in order to investigate the robustness of the proposed parameter estimation method. The hydraulic model of the operational WDN and the acquired hydraulic data are provided as supplementary data to enable the comparisonof hydraulic model calibration methods with operational data and encourage reproducible research
Nerantzis D, Pecci F, Stoianov I, 2020, Optimal control of water distribution networks without storage, European Journal of Operational Research, Vol: 284, Pages: 345-354, ISSN: 0377-2217
The paper investigates the problem of optimal control of water distribution networks without storage capacity. Using mathematical optimization, we formulate and solve the problem as a non-convex NLP, in order to obtain optimal control curves for both variable speed pumps and pressure reducing valves of the network and thus propose a methodology for the automated control of real operational networks. We consider both single-objective and multi-objective problems with average zonal pressure, pump energy consumption and water treatment cost as objectives. Furthermore, we investigate global optimality bounds for the calculated solutions using global optimization techniques. The proposed approach is shown to outperform state-of-the-art global optimization solvers. The described procedure is demonstrated in a case study using a large size operational network.
Blocher C, Pecci F, Stoianov I, 2020, Localizing leakage hotspots in water distribution networks via the regularization of an inverse problem, Journal of Hydraulic Engineering, Vol: 146, Pages: 04020025-1-04020025-13, ISSN: 0733-9429
The ill-posed inverse problem for detecting and localizing leakage hotspots is solved using a novel optimization-based method which aims to minimize the difference between hydraulic measurement data and simulated steady states of a water distribution network. Regularization constrains the set of leak candidate nodes obtained from a solution to the optimization problem. Hydraulic conservation laws are enforced as nonlinear constraints. The resulting nonconvex optimization problem is solved using smooth mathematical optimization techniques. The solution identifies leakage hotspot areas, which can then be further investigated with alternative methods for precise leak localization. A metric is proposed to quantitatively assess the performance of the developed leak localization approach in comparison with a method that uses the sensitivity matrix. In addition, we propose a strategy to select the regularization parameter when large-scale operational networks are considered. Using two numerical case studies, we demonstrate that the proposed approach outperforms the sensitivity matrix method, with regards to leak isolation, in most single leak scenarios. Moreover, the developed method enables the localization of multiple simultaneous leaks.
Scoular JM, Croft J, Ghail RC, et al., 2019, Limitations of persistent scatterer interferometry to measure small seasonal ground movements in an urban environment, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 53, Pages: 39-48, ISSN: 1470-9236
London Clay, which underlies the majority of Greater London, has a high shrink–swell potential that can result in damage to foundations and surface infrastructure due to seasonal expansion and contraction of the clay. Currently, surface movement as a result of shrink–swell is not monitored in London, meaning that the magnitude and cyclicity of these movements is poorly understood. Persistent Scatterer Interferometric (PSI) Synthetic Aperture Radar data provide high-precision line-of-sight displacement measurements at a high point density across urban areas, offering the possibility of routine shrink–swell monitoring across whole cities. To test this, PSI data derived from TerraSAR-X (TSX) observations for the period from May 2011 to April 2017 were analysed for shrink–swell patterns across three areas of London in Hammersmith, Muswell Hill and Islington. A consistent cyclicity and amplitude was detected at all sites and the number of cycles is comparable with those identified in rainfall data. The amplitude of these cycles is smaller than anticipated, most probably because of the resisting effect of roads and pavements. The Cranfield University Leakage Assessment from Corrosivity and Shrinkage (LEACS) database was used to subdivide the PSI data and the average velocity and amplitude of each class statistically tested for significant differences between classes. The results show that it is not possible to statistically isolate possible soil shrink–swell movement in TSX PSI data in London.
Changklom J, Stoianov I, 2019, Redundant flow estimation methods for robust hydraulic control in water supply networks, Journal of Hydroinformatics, Vol: 21, Pages: 571-592, ISSN: 1464-7141
The implementation of robust hydraulic control in water supply networks relies upon the utilisation of redundant flow estimation methods. In this paper, we propose a novel model-based flow estimation method for diaphragm actuated globe valves based on three pressure signals, namely the valve inlet pressure, valve outlet pressure and control chamber pressure (the 3P flow estimation method). The proposed flow estimation method relies upon the accurate determination of a valve stem position based on a force balance analysis for the diaphragm of a valve, the measured pressure differential across a valve and the flow coefficients of a valve (Cv, Kv). A novel stem position estimation model for diaphragm actuated globe valves has been formulated and experimentally validated. The non-linear parameterised valve stem position estimation model results in multiple solutions. We combine advances in signal processing with support vector machine classification to find a correct solution. We compare the proposed 3P flow estimation method with a method, which uses stem position sensor measurements of a valve and two pressure signals. A unique set of experimental data have been acquired for performance validation. We derive uncertainty bounds for the proposed flow estimation method and demonstrate its application for robust pressure control in water supply networks.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.