1,720,978 research outputs found
The Influence of Soil Stochastic Heterogeneity and Facility Dimensions on Stormwater Infiltration Facilities Performance
No full textThe progressive increase of impervious surfaces induced by urbanization altered significantly the natural hydrological cycle of urban catchments. To face the need of more sustainable and effective solutions for stormwater management and planning, Low Impact Development (LID) practices have been frequently proposed to support existing urban drainage systems. Among LID infrastructures, design and management of stormwater infiltration facilities are still characterised by a high degree of uncertainty. Since the stochastic heterogeneity of the soil may affect significantly their hydraulic performance, it is crucial to understand whether it should be accounted for in the design process. To this aim, numerical experiments under transient variably water saturated conditions were performed. Four infiltration facilities of different bottom length subjected to the same spatial variability of the intrinsic permeability field were considered. Simulations showed that the effects of stochastic heterogeneity on the hydraulic performance are dependent on the dimensions of the facility and on the correlation lengths of the intrinsic permeability field. These effects may potentially undermine the capacity to capture stormwater. To be reduced, the bottom dimensions of the facility should be higher than the horizontal correlation lengths of the intrinsic permeability field. Most strikingly, whether the stochastic heterogeneity is considered or not, the volume infiltrated through the bottom follows an increasing power law with increasing bottom length, while the average infiltration rate at the bottom follows a decaying power law
Closure to "boosting Genetic Algorithm Performance in Pump Scheduling Problems with a Novel Decision-Variable Representation" by Luigi Cimorelli, Andrea D'Aniello, and Luca Cozzolino
No full textLeaking pipes and the urban karst: a pipe scale numerical investigation on water leaks flow paths in the subsurface
No full textMillions of cubic meters of water are lost every year from water utilities, with detrimental consequences on the environment and on society. However, this large amount of water is not necessarily lost. Although leaking water utilities have the potential to recharge urban aquifers, very little is known about the fate of leaked water and its interaction with subsurface anthropogenic features, such as the high permeability trenches surrounding utility pipelines. As these features are deemed to create preferential pathways, it is crucial to understand if these can reduce urban aquifers recharge by interception and diversion of water leaked. Through a series of transient 3D numerical simulations under a variety of conditions (i.e., different native soil properties, slopes of the utility trench, depths of the groundwater table, and leak rates), this study provides evidence that utility trenches can potentially alter the migration pathway of water leaked from utility pipelines located above the groundwater table. Therefore, the urban karst effect has the potential to occur directly at the utility trench. Indeed, from roughly 55% up to 73% of the water leaked is retained within the utility trench and does not reach the underlying aquifer in one third of the scenarios modeled. This occurs because of the combined effect of soil retention properties, initial effective water saturation, relative permeability, and intrinsic permeability. Although this analysis is still preliminary, these results potentially challenge the traditional concept of leaking pipes recharging groundwater
Optimal regulation of pumping station in water distribution networks using constant and variable speed pumps: A technical and economical comparison
Full text linkGreenhouse gas emission is one of the main environmental issues of today, and energy savings in all industries contribute to reducing energy demand, implying, in turn, less carbon emissions into the atmosphere. In this framework, water pumping systems are one of the most energy-consuming activities. The optimal regulation of pumping systems with the use of variable speed drives is gaining the attention of designers and managing authorities. However, optimal management and operation of pumping systems is often performed, employing variable speed drives without considering if the energy savings are enough to justify their purchasing and installation costs. In this paper, the authors compare two optimal pump scheduling techniques, optimal regulation of constant speed pumps by an optimal ON/OFF sequence and optimal regulation with a variable speed pump. Much of the attention is devoted to the analysis of the costs involved in a hypothetical managing authority for the water distribution system in order to determine whether the savings in operating costs is enough to justify the employment of variable speed drives
Analytical solutions of the linearized parabolic wave accounting for downstream boundary condition and uniform lateral inflows
No full textIn this paper, new analytical solutions of the linearized parabolic approximation (LPA) of the De Saint Venant equations (DSVEs) are derived for the case of finite channel length. The new solutions, which take into account upstream and lateral inflows, are found considering two types of boundary conditions at the downstream end, namely a stage–discharge relationship and a time dependent flow depth. The solutions, for both discharge and water depth, are first determined in the Laplace Transform domain, and the Laplace Transform Inversion Theorem is used in order to find the corresponding time domain expressions. Finally, the effects induced on the flow propagation by the downstream boundary condition are analyzed using the new analytical solutions
Leakage Area Detection in Water Distribution Networks: a Two-Step Algorithm Using Limited Data
No full textThis paper presents a two-step algorithm for leak detection in Water Distribution Networks (WDNs). In the first step, a minimization process based on a derivative-free optimizer reduces the difference between simulated and measured data at the respective pressure/flow sensors installed within the WDN. Leakage coefficients serve as decision variables, each unequivocally associated with a specific location within the network. In the second step, a filtering-clustering-ranking algorithm eliminates nodes where the leaked volume is considered negligible, identifies leakage clusters, and generates a priority list of nodes for further inspection using leak isolation or pinpointing techniques. The proposed algorithm falls within the category of leakage awareness models; therefore, it is not designed to perfectly localize leaks but rather to narrow down the leakage area, facilitating subsequent on-field localization efforts. Tests conducted on a realistic WDN demonstrated promising performance, as the algorithm successfully restricted the leakage area—sometimes even pinpointing the exact location—using a limited number of pressure/flow sensors, despite varying leak magnitudes and locations across the network. Preliminary tests also indicated that the algorithm performs well in scenarios involving multiple leaks. Overall, the proposed model was capable of including the leaking node within a priority list 96% of the time, considering all the parameter settings used and all the leakage scenarios considered
A Novel Generalized Semi-Analytical Approach for Flood Control Reservoir Design
Full text linkFlood control reservoir design requires estimating the total storable water volume or the maximum allowable discharge. This study proposes a novel Generalized Semi-Analytical Approach (GS-AA) to identify the maximum outlet discharge a flood control reservoir can handle for a specific return period. The approach exploits the analytical expression of Flow Duration Reduction (FDR) curves and combines them with an optimization algorithm to find the critical hydrograph and, thus, the hydrograph providing the maximum outlet discharge from the reservoir. The approach models the runoff process of the basin upstream of the reservoir, allowing users to choose any runoff model (RM). The proposed approach shows faster computational times than a fully numerical procedure, enabling potential users to explore and compare multiple reservoir configurations easily. Moreover, this approach addresses flow data limitation issues that prevent FDR curve derivation by correlating them to Intensity Duration Frequency curve parameters, expanding the potential applicability of the procedure in ungauged basins. Finally, results demonstrated the functionality of the procedure regardless of the chosen RM, offering widespread flexibility for users. The proposed GS-AA is a robust and adaptable tool for design and verification purposes to improve flood management strategies
An improved numerical scheme for the approximate solution of the Parabolic Wave model
No full textIn this paper the main features and performances of a new numerical scheme, ILILPM (Improved Locally and Instantaneously Linearized Parabolic Model) are described. ILILPM is an improved version of the Parabolic and Backwater (PAB) and Linearized Parabolic Model (LPM) schemes, proposed in literature for the approximate solution of the Parabolic Wave model. The algorithm presented is able to take into account transcritical flow regime and transitions from free-surface to pressurized flow in tree-like channel networks. Due to its unconditional stability, the model allows large computational time steps, leading to very fast simulations during transients for a class of flow conditions larger than those solved by the parent schemes. The model is demonstrated by comparing its results with experimental observations and with the results provided by the numerical solution of the full De Saint-Venant equations
Comparison Among Resilience and Entropy Index in the Optimal Rehabilitation of Water Distribution Networks Under Limited-Budgets
No full textThe replacement of existing pipes is a strategy for the rehabilitation of water distribution networks that is frequently adopted by water companies. Usually, the optimal choice of the pipes diameter is a difficult optimization task, because limited budgets are available. In order to support the selection of a rehabilitation strategy, surrogate reliability measures are often used as an indirect measure of the water distribution system hydraulic performance. Among others, the resilience and entropy indices have attracted considerable interest because they both represent a measure of the network robustness. In the present work, a comparison between these indices is provided in the framework of the optimal rehabilitation of an existing network under limited budget constraint. The resilience and entropy indices are applied to the case of a realistic water distribution network in an extended period simulation framework. Several values of the maximum budget allocable for rehabilitation are considered, and hydraulic calculations are undertaken by means of a pressure driven approach within a modified EPANET 2 environment. The effectiveness of the two surrogate reliability measures is demonstrated by an a-posteriori reliability assessmen
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