1,721,041 research outputs found
Identifying the High-level Flow Model of Water Distribution Networks Using Graph Theory
No full textAbstractIdentifying the main connections between water production, processing and distribution sites can give a clearer comprehension of their structure, importance and criticality. We present a graph-theory based approach which is able to dramatically reduce the complexity of a network to allow a better comprehension of its main flow models. As a starting point, some nodes in the network are marked as primary;A skeletonization procedure then reduces the graph excluding all the pipes which are not essential to connect the primary nodes. The network is further analysed to define a single path between couples of primary nodes. An efficient implementation (in Python+IGraph) is discussed, along with performance improvements. The results can be employed to understand the flow model of a previously unknown network or as a first step to determine its most vulnerable or important elements
Comparison among best solutions of the optimal design of water distribution networks obtained with different algorithms
No full textThe optimal design of water distribution networks is a complex problem even in its simplest formulation, where only the maintenance of a minimum pressure is required. This paper compares the best solutions obtained using different optimization algorithms: the BONMIN Branch and Bound algorithm, which directly tackles the MINLP (mixed integer non-linear programming) formulation, and two heuristic algorithms, i.e. GHEST (genetic heritage evolution by stochastic transmission) and an island parallel implementation of the multi-objective algorithm NSGA-II. In addition, the best solutions are compared with the actual diameter configuration of the network in terms of cost and of hydraulic behaviour. The three algorithms are applied to the hydraulic model of Modena water distribution network that takes into account the main pipes
Genetic Heritage Evolution by Stochastic Transmission in the optimal design of water distribution networks
No full textAndrea Bolognesi, Cristiana Bragalli, Angela Marchin and Sandro Artinahttp://www.elsevier.com/wps/find/journaldescription.cws_home/422911/description#descriptio
Contributo dell'algoritmo euristico ghest nella caratterizzazione energetica di una rete di distribuzione idrica
Full text linkUn sistema di distribuzione idropotabile (Water Distribution Network -WDN), data la sua complessità strutturale e funzionale, per l' ordinario esercizio richiede elevati quantitativi di energia. L'attuale trend tecnico/scientifico incoraggia la loro gestione e progettazione nell'ottica di un generale risparmio di energia che, oltre ad un indiscusso vantaggio economico, implica sopratutto una razionalizzazione dell'impiego di risorsa idrica.
Questo è il contesto scientifico/culturale in cui il presente elaborato si colloca. Nello specifico, ci si propone la caratterizzazione energetica di la rete di distribuzione idrica Cabrera_network.(rivisitazione della rete presentata da E.Cabrera e M.Pardo nel loro studio del 2010) .
Si sono quindi qualificati i legami tra i consumi energetici ed aspetti, quali: dimensionamento dei condotti, perdite idriche, tipologia di pompa centrifuga sfruttata e livello idrico massimo del serbatoio di compenso. Ciò è stato esplicato in due fasi di analisi. In una primo momento, si sono impiegati strumenti classi quali il simulatore idraulico Epanet2 e i fogli di calcolo Excel. In un secondo momento, il problema dell'ottimizzazione energetica della rete è stato risolto a mezzo l'algoritmo euristico GHEST.
Al di là delle specifiche conclusioni, cui si rinvia, l'elaborato consente di cogliere un più generale profilo di ordine metodologico: l'importanza di una visione d'insieme del problema energetico in un sistema di distribuzione idropotabile, dalla quale, nel caso di specie, emerge che la scelta più ragionevole, al fine dell'ottimizzazione energetica, consiste nell'individuazione del più idoneo modello di pompa alimentante la rete. Per poi, data l'onere progettuale e applicativo che comporta, provvedere al reinvestimento dei capitali risparmiati in attività volte alla riduzione delle perdite idriche. Sono questi infatti, i due aspetti che più incidono sui consumi energetici nel caso di studio
Analisi degli aspetti di qualità nella gestione dei sistemi di drenaggio urbano attraverso modellazione numerica e indagini di campo
No full textIn order to protect river water quality, highly affected in urban areas by continuos as
intermittent immissions, it is necessary to adopt measures to intercept and treat these
polluted flows.
In particular during rain events, river water quality is affected by CSOs activation. Built
in order to protect the sewer system and the WWTP by increased flows due to heavy
rains, CSOs divert excess flows to the receiving water body.
On the basis of several scientific papers, and of direct evidences as well, that
demonstrate the detrimental effect of CSOs discharges, also the legislative framework
moved towards a stream standard point of view.
The WFD (EU/69/2000) sets new goals for receiving water quality, and groundwater as
well, through an integrated immission/emissions phylosophy, in which emission limits
are associated with effluent standards, based on the receiving water characteristics and
their specific use.
For surface waters the objective is that of a “good” ecological and chemical quality
status. A surface water is defined as of good ecological quality if there is only slight
departure from the biological community that would be expected in conditions of
minimal anthropogenic impact. Each Member State authority is responsible for
preparing and implementing a River Basin Management Plan to achieve the good
ecological quality, and comply with WFD requirements.
In order to cope with WFD targets, and thus to improve urban receiving water quality, a
CSOs control strategy need to be implemented. Temporarily storing the overflow (or at
least part of it) into tanks and treating it in the WWTP, after the end of the storm,
showed good results in reducing total pollutant mass spilled into the receiving river.
Italian State Authority, in order to comply with WFD statements, sets general
framework, and each Region has to adopt a Water Remediation Plan (PTA, Piano
Tutela Acque), setting goals, methods, and terms, to improve river water quality. Emilia
Romagna PTA sets 25% reduction up to 2008, and 50% reduction up to 2015 fo total
pollutants masses delivered by CSOs spills.
In order to plan remediation actions, a deep insight into spills dynamics is thus of great
importance.
The present thesis tries to understand spills dynamics through a numerical and an
experimental approach. A four months monitoring and sampling campaign was set on
the Bologna sewer network, and on the Navile Channel, that is the WWTP receiving
water , and that receives flows from up to 28 CSOs during rain events. On the other
hand, the full model of the sewer network, was build with the commercial software
InfoWorks CS.
The model was either calibrated with the data from the monitoring and sampling
campaign. Through further model simulations interdependencies among masses spilled,
rain characteristics and basin characteristics are looked for.
The thesis can be seen as a basis for further insighs and for planning remediation
actions
Experimental and numerical analyses about the efficiency of flow through devices for the sediment controll in urban runoff
No full textAs land is developed, the impervious surfaces that are created increase the amount of runoff during rainfall events, disrupting the natural hydrologic cycle, with an increment in volume of runoff and in pollutant loadings. Pollutants deposited or derived from an activity on the land surface will likely end up in stormwater runoff in some concentration, such as nutrients, sediment, heavy metals, hydrocarbons, gasoline additives, pathogens, deicers, herbicides and pesticides. Several of these pollutants are particulate-bound, so it appears clear that sediment removal can provide significant water-quality improvements and it appears to be important the knowledge of the ability of stromwater treatment devices to retain particulate matter. For this reason three different units which remove sediments have been tested through laboratory. In particular a roadside gully pot has been tested under steady hydraulic conditions, varying the characteristics of the influent solids (diameter, particle size distribution and specific gravity). The efficiency in terms of particles retained has been evaluated as a function of influent flow rate and particles characteristics; results have been compared to efficiency evaluated applying an overflow rate model. Furthermore the role of particles settling velocity in efficiency determination has been investigated. After the experimental runs on the gully pot, a standard full-scale model of an hydrodynamic separator (HS) has been tested under unsteady influent flow rate condition, and constant solid concentration at the input. The results presented in this study illustrate that particle separation efficiency of the unit is predominately influenced by operating flow rate, which strongly affects the particles and hydraulic residence time of the system. The efficiency data have been compared to results obtained from a modified overflow rate model; moreover the residence time distribution has been experimentally determined through tracer analyses for several steady flow rates. Finally three testing experiments have been performed for two different configurations of a full-scale model of a clarifier (linear and crenulated) under unsteady influent flow rate condition, and constant solid concentration at the input. The results illustrate that particle separation efficiency of the unit is predominately influenced by the configuration of the unit itself. Turbidity measures have been used to compare turbidity with the suspended sediments concentration, in order to find a correlation between these two values, which can allow to have a measure of the sediments concentration simply installing a turbidity probe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
