1,721,078 research outputs found
Scaling models of intensity–duration–frequency (IDF) curves based on adjusted design event durations
No full textThis paper deals with intensity–duration–frequency (IDF) curves, which express the relationship between average rainfall intensity and event duration for various probabilities of non-exceedance (or return periods) for the design/analysis of hydraulic interventions and infrastructures in riverine and urban drainage contexts. New scaling models are proposed to develop a single IDF model valid for all durations, from below 1 h to 24 h. In these models, the scale invariance is applied to rainfall intensity to obtain a parsimonious IDF structure capable of defining a family of IDF curves at various return periods. The main novelty consists of the formulation of simple and multiple scale invariance based on adjusted design event durations. The parameterization is carried out in two phases: in the first phase, the adjustment size is searched for iteratively while the other parameters of the IDF structure are directly obtained in cascade; in the second phase, which enables considering different reliability levels for extreme rainfall data as a function of sample length at different durations, parameter refinement is carried out by means of a local optimization algorithm. The second step accommodates data samples of different extension as a function of available data at different durations. The application to four case studies at various latitudes in Europe, namely Helsinborg (Sweden), Frauenwald (Germany), Pavia and Erice (Italy), proves the IDF structure to fit well the quantile predictions of extreme rainfall data for specified durations below and above one hour
Hydraulic and economic analysis of real time control
No full textThe aim of this paper is to analyze the hydraulic and economic effectiveness of the real-Time control (RTC) of pressure reducing valves (PRVs), for the purpose of managing pressure to reduce leakage and pipe bursts. In their conventional use, a PRV automatically reduces a higher inlet pressure to a lower downstream set-point pressure (steady-state), regardless of changing flow rate or varying inlet pressure. In local RTC, instead, the set-point can be adjusted in real time to accommodate the variations in the water discharge though the valve. In detail, local RTC is performed thanks to a programmable logic controller (PLC), which can use the water discharge measurement received from an electromagnetic flowmeter in proximity to the valve, to calculate a new valve setting. The initial applications of the work will concern the extended period simulation of a pressure zone, in which the locally controlled PRVs is installed in the feed pipe that connects the source to the pressure zone. In this case study, nodal demands are reconstructed stochastically through the bottom-up approach and the relationship between downstream set-point pressure and water discharge through the device is derived in such a way as to meet users' pressure requirements at all nodes. The subsequent sections describe the assessment of the total cost of the controlled system, including the installation cost of the control device, the flow-dependent operation and maintenance (O&M) cost, and the pipe burst repair cost over the planning horizon. The total cost of the local RTC will be compared with that of three other scenarios: 1) no control, 2) conventional PRV and 3) remote RTC under various conditions of system size, demand pattern and leakage. The analysis shows that conventional PRV's are most appropriate for small pressure zones, with limited leakage and low-cost water while real time control is needed in larger zones, with high leakage and high-cost water
Using Additional Time Slots for Improving Pump Control Optimization Based on Trigger Levels
No full textThis paper presents a new methodology for optimizing the operation of pumps supplying water from a low source to an elevated tank in water distribution systems (WDSs). It is based on the use of the on/off trigger level technique for each pump present in the pumping station. The novelty of the methodology consists of the addition of time slots for the optimization of the trigger levels. These slots are created at the end of each energy tariff period, to drive the tank level to the highest and lowest points at the beginning and at the end of the peak, respectively. As a result, pumps are led to work more and less during low and high tariff periods, respectively, yielding reductions in energy costs. In the applications, the methodology was introduced within a multi-objective optimization framework, searching for solutions in the trade-off between daily average energy cost and daily average number of pump switches, representative of the stressing conditions for the system. The methodology was applied to case studies with single and multiple pumps, using realistic demand patterns, and was compared with other trigger levels-based methodologies in the scientific literature. The results proved its benefits, in yielding solutions with reduced number of pump switches for prefixed values of energy cost. This is more evident when the operation of three pumps must be optimized. In an explicative example with three operating pumps, for an energy cost around 6000 €/day, the newly proposed methodology leads to a number of pump switches between 17% and 33% lower than the results obtained with the methods considered for comparison
Multiobjective Optimization of Control Valve Installation and DMA Creation for Reducing Leakage in Water Distribution Networks
No full textThis paper presents a novel methodology for optimizing simultaneously the installation of control valves and the creation of district metered areas (DMAs) in water distribution networks (WDNs). This methodology was developed through the multiobjective approach, by considering, as decisional variables, the sites for control valve installation and isolation valve closure. The proposed algorithm is based on the hybrid combination of three algorithms, a multiobjective genetic algorithm, which is entrusted with valve site search, and two embedded algorithms, the first based on iterated linear programming (LP) and the second based on graph theory, aimed at searching for the optimal settings of control valves and at partitioning the WDN into DMAs, respectively. The hybrid algorithm attempts to find optimal solutions in the trade-off between the following objective functions to be optimized simultaneously: total installation cost, daily leakage volume, and demand uniformity across DMAs. The applications to a small Lebanese WDN proved that the methodology can find, especially for high values of the total installation cost, effective control valve installations, and isolation valve closures in terms of leakage abatement while obtaining a uniform distribution of demands across DMAs
Closure to "peak Demand Assessment and Hydraulic Analysis in WDN Design" by E. Creaco, P. Signori, S. Papiri, and C. Ciaponi
No full textA Dynamic Adaptive Approach for Water Distribution Network Design
Full text linkThis is the author accepted manuscript. The final version is available from American Society of Civil Engineers via the DOI in this record In the face of a highly uncertain future, there is a need for water utilities to develop structured approaches for the long-term strategic design of water distribution networks (WDNs). A new conceptual framework for developing an integrative approach based on a multicriteria decision analysis (MCDA), embracing an optimization model to size flexible alternatives, is proposed. The flexible solutions are evaluated through MCDA for all the criteria (investment costs, carbon emissions, resilience, and reliability of WDNs) across all the scenarios generated for the sake of robustness and will help to adapt WDNs to changing conditions over a long planning horizon, divided into phases. The alternatives are ranked through two different MCDA methods, Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), so that decision makers will have more comprehensive information for analyzing highly ranked design solutions and after the first phase, solutions for the other phases can be reassessed by the same dynamic adaptive framework
Service Pressure and Energy Consumption Mitigation-Oriented Partitioning of Closed Water Distribution Networks
No full textThis paper presents the partitioning of the closed water distribution network (WDN) serving the city of Pavia, Italy. As a thus far poorly explored aspect in the scientific literature, clustering for the definition of size and extension of district metered areas (DMAs) and of inter-DMA boundary pipes is performed by ensuring that the DMAs respect the altimetric areas of the WDN by leaning on a modified formulation of modularity. To define the boundary pipes to be closed or alternatively fitted with a flow meter for the monitoring of DMA consumption, the dividing is performed with an innovative heuristic algorithm. This technique operates by sequentially implementing the boundary closures that do not cause significant head losses, to obtain an approximation of the Pareto front in the trade-off between number of flow meters installed and WDN reliability. In the last part of the work, the pumps present in the network are assumed to be equipped with the variable speed drive, and their hourly settings are optimized to regulate service pressure. Overall, WDN partitioning and pump setting optimization are proven to mitigate the service pressure and energy consumption of the WDN, offering evident and attractive benefits up to about 50% for water utilities
Nondimensional simulation-based regression formulas for slit dam design in mountain rivers
No full textCompact regression formulas were developed through one-dimensional (1D) unsteady flow numerical model simulations for the analysis of slit dam (SD) hydraulic behavior in torrents. The formulas allow an easy evaluation of the sediment-trapping efficiency and of the depth of the sediment deposit upstream from SDs at the peak time of flood. The use of the developed formulas also provides a first estimation of the dam self-cleaning effects at the end of the event associated with the receding stage of the hydrograph. Compared to the approaches available in the literature, the results of this work allow the extension of the analysis of the trapping processes behind SDs to conditions of unsteady flow. The developed formulas may represent a simple and reliable tool for SD design in mountain gravel bed rivers characterized by relatively steep slopes (1-5%)
The in situ approach to model identification and control design for pressure regulation in Water Distribution Networks: An in silico evaluation
No full textIn the context of Water Distribution Networks, service pressure regulation is an important technique that allows reductions in leakage, risk of pipe bursts and mechanical stress to the infrastructure. Recent works demonstrated in silico, i.e. numerically, that linear control systems can be effectively adopted for this task, provided that a careful tuning is performed. Specifically, the tuning should be based on high order, linear models, which describe the system dynamics around a nominal working point. These models can be straightforwardly derived in a simulated environment, but their in situ identification may be challenging due to the presence of non-measurable, exogenous disturbances. This work moves a step forward towards the application of service pressure regulation in situ, by proposing an effective model identification approach for the linear models, based on spectral analysis. The novel approach can cope with exogenous, non-measured disturbances acting during the identification experiments, and considers possible constraints limiting the experimental design. Moreover, the models identified in the in situ conditions are exploited to synthesise linear regulators and assess the closed-loop performances of the overall control methodology. Though being presented and tested in silico, this work assumes a strong practical relevance in view of the results achieved. It in fact demonstrates that novel control schemes, previously designed in nominal conditions only, can be actually designed and implemented in a real scenario, thus making pressure control safer, more reliable and more effective. Finally, the numerical analysis allows for a comparison of both identification and control results with to those obtained in nominal conditions, to provide further insight and stress the reliability of the proposed methodology
Testing an innovative first flush identification methodology against field data from an Italian catchment
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