Sensitivity Analysis and Calibration of a Rainfall-runoff Model with the Combined Use of EPA-SWMM and Genetic Algorithm

An integrated Visual Basic Application interface is described that allows for sensitivity analysis, calibration and routing of hydraulichydrological models. The routine consists in the combination of three freeware tools performing hydrological modelling, hydraulic modelling and calibration. With such an approach, calibration is made possible even if information about sewers geometrical features is incomplete. Model parameters involve storage coefficient, time of concentration, runoff coefficient, initial abstraction and Manning coefficient; literature formulas are considered and manipulated to obtain novel expressions and variation ranges. A sensitivity analysis with a local method is performed to obtain information about collinearity among parameters and a ranking of influence. The least important parameters are given a fixed value, and for the remaining ones calibration is performed by means of a genetic algorithm implemented in GANetXL. Single-event calibration is performed with a selection of six rainfall events, which are chosen so to avoid non-uniform rainfall distribution; results are then successfully validated with a sequence of four events

Hydraulic Design of a USBR Type II Stilling Basin

The present paper deals with a United States Bureau of Reclamation (USBR) Type II stilling basin, which is characterized by blocks at the end of the chute and a dentated sill at the end of the basin. For this basin, USBR only gives overall design criteria concerning basin length and block dimensions on the basis of the assumption that the hydraulic jump remains confined within the sill. No considerations are provided concerning possible different jump types, pressure regimes, and forces acting on the sill. To comply with such a lack, an experimental campaign was undertaken that focuses on the differences among hydraulic jump types that can occur in a USBR Type II stilling basin. Jump types can range between submerged and spray jump types; accordingly, dimensionless relations are provided to predict jump type and position for assigned boundary conditions, with particular concern about the submerged/nonsubmerged distinction. Considerations about the drag force and drag coefficients are provided, along with estimates of pressure extreme fluctuations. Finally, an evaluation of the dissipation efficiency is presented for both submerged and nonsubmerged jumps, enabling comparisons among different jump types and with classical hydraulic jump. - See more at: http://ascelibrary.org/doi/abs/10.1061/(ASCE)IR.1943-4774.0001150#sthash.ajmk3TuB.dpu

Optimal pump scheduling for urban drainage under variable flow conditions

The paper is focused on the optimal scheduling of a drainage pumping station, complying with variations in the pump rotational speed and a recurrent pattern for the inflow discharge. The paper is structured in several consecutive steps. In the first step, the experimental set-up is described and results of calibration tests on different pumping machines are presented to obtain equations linking significant variables (discharge, head, power, efficiency). Then, those equations are utilized to build a mixed-integer optimization model able to find the scheduling solution that minimizes required pumping energy. The model is solved with respect to a case study referred to a urban drainage system in Naples (Italy) and optimization results are analysed to provide insights on the algorithm computational performance and on the influence of pumping machine characteristics on the overall efficiency savings. With reference to the simulated scenarios, an average value of 32% energy can be saved with an optimized control. Its actual value depends on the hydraulic characteristics of the system

Experimental results on the physical model of an USBR type II stilling basin

The present paper describes the experimental campaign carried on the physical model of the spillway of Lower Diamphwe Dam (Malawi), which is provided with a USBR type II stilling basin. Stilling basins are used in order to reduce the excessive kinetic energy of flowing water downstream of spillways. Specifically, a USBR type II basin is provided with blocks at the end of the chute and with a confining dentated sill; these appurtenances allow to dissipate excess energy with high efficiency. The study focuses on the hydraulic behavior of the stilling basin; tests were carried on for different values of incoming discharge and downstream water depth. Results show the dissipation efficiency of the stilling basin in terms of pressure fluctuation and the variability of the jump type with the hydraulic characteristics of the incoming and the downstream flow depths

Comparing Different Modelling Strategies for the Estimation of Climate Change Effects on Urban Pluvial Flooding

In this paper, two different strategies are presented that allow for the assessment of the effects of climate change on urban pluvial flooding, in order to understand potentialities and limitations, advantages and drawbacks. The two strategies are hereby defined as “top-down” and “bottom-up”, according to the relative position of climate change modelling with respect to flood modelling (upstream for top-down, downstream for bottom-up). To provide a practical example, the two strategies are applied to a case study located in Naples, Italy. However, they can be successfully extended for the assessment of any potential impact of climate change in any location

Indagine sperimentale su manufatti di scarico e derivazione nelle reti di drenaggio urbano

Il presente elaborato prende le mosse dalle attività di ammodernamento della rete fognaria della città di Napoli, nell'ambito della quale si è resa necessaria un'attività sperimentale al fine di determinare i meccanismi di deflusso di due diversi manufatti idraulici. Il primo manufatto oggetto di interesse è il cosiddetto partitore semifrontale, una tipologia innovativa di scaricatore di piena poco ingombrante e particolarmente adatto ad essere utilizzato in corrente veloce, costituito da un canale rettangolare posizionato all'interno del canale principale. Le variabili del sistema sono la distanza del fondo del canale derivatore dal fondo del canale principale, ed in particolare il suo rapporto con il tirante della corrente principale, e la larghezza del derivatore, rapportata alla larghezza del canale principale. La sperimentazione, condotta realizzando un modello in similitudine di Froude dell'area di interesse, con un rapporto di scala delle lunghezze pari a 0.15, ha portato alla definizione della scala di deflusso del partitore; tale equazione descrive in sostanza il rapporto di partizione, ovvero il rapporto tra la portata defluente nel derivatore e quella defluente nel canale principale, come coincidente con il rapporto tra le sezioni rispettivamente occupate dalle due correnti. La scala di deflusso, opportunamente espressa in termini adimensionali, costituisce il criterio di progettazione incognito del manufatto; tramite essa è infatti possibile scegliere le dimensioni da assegnare al partitore note che siano le caratteristiche della corrente in arrivo al sistema e il valore della portata da derivare. La sperimentazione ha inoltre consentito di trarre alcune conclusioni circa l'efficienza del partitore, in buona sostanza analoga a quella di simili sistemi di partizione di portata, e riguardo il raggiungimento della condizione di stato critico, che costituisce il limite superiore, in termini di portata, di utilizzo del manufatto. Il secondo manufatto oggetto di studio è un pozzo di caduta ad asse verticale con imbocco a spigolo vivo. Tale sistema, pur non essendo innovativo nel panorama tecnico internazionale, non risulta tuttavia adeguatamente caratterizzato dal punto di vista progettuale; la letteratura tecnica si limita infatti a fornire delle considerazioni generiche, per lo più mutuate da studi condotti su pozzi caratterizzati da altri tipi di imbocco. La sperimentazione è stata condotta facendo variare i principali parametri del sistema, quali la lunghezza e il diametro del pozzo; si è inoltre deciso di introdurre un sistema di aerazione consistente in un tubo aeroforo coassiale al pozzo, per il quale si sono impiegati diversi diametri e diversi gradi di affondamento dello stesso all'interno del pozzo. L'analisi ha consentito innanzitutto di definire la peculiare forma della scala di deflusso, costituita da tre diversi segmenti corrispondenti a tre diversi regimi di deflusso che possono realizzarsi all'interno del sistema al variare di portata e tirante. Quindi, i dati sperimentali hanno consentito di individuare una relazione fisicamente basata tra la portata defluente nel pozzo e il carico sulla sezione di imbocco, valida in regime di pressurizzazione e atta ad essere utilizzata come criterio di progettazione del manufatto per tale condizione. Più difficile risulta invece l'interpretazione analitica dei restanti regimi di deflusso, i quali tuttavia sono possibili solo per valori modesti di portata e tirante e risultano, da questo punto di vista, meno gravosi per il manufatto; un'ulteriore complicazione allo studio del fenomeno è dato dalla presenza di fenomeni vorticosi che influiscono sulle condizioni di deflusso all'interno del pozzo, apportando notevoli quantità di aria e variando notevolmente le condizioni interne di pressione

A Mixed Strategy Based on Self-Organizing Map for Water Demand Pattern Profiling of Large-Size Smart Water Grid Data

In the present paper a procedure is introduced to detect water consumption patterns within water distribution systems. The analysis is based on hourly consumption data referred to single-household flow meters, connected to the Smart Water Network of Soccavo (Naples, Italy). The procedure is structured in two consecutive phases, namely clustering and classification. Clustering is performed on a selection of standardized monthly time series, randomly chosen within the database; different clustering models are tested, basing on K-means, dendrogram and Self-Organizing Map, and the most performant is identified comparing a selection of Clustering Validity Indices. Supervised classification is performed on the remaining time series to associate unlabeled patterns to the previously defined clusters. Final results show that the proposed procedure is able to detect annual patterns describing significant customers behaviors, along with patterns related to instrumental errors and to abnormal consumptions

Transitional and Weir Flow in a Vented Drop Shaft with a Sharp-Edged Intake

An experimental analysis of a vertical drop shaft with a sharp-edged horizontal intake section and a coaxial venting pipe is undertaken to obtain design criteria given the limited attention provided by literature. Three different flow regimes are observed, namely weir flow and pressurized flow for extreme discharges and transitional flow for intermediate discharges. Particular attention is paid to transitional flow, which is a periodical regime consisting of an alternate switch from weir to pressurized flow, with water heads ranging between a maximum and a minimum. For transitional flow a detailed characterization of water surface oscillations is provided, and nondimensional equations are given describing mean water head, oscillation amplitude and frequency as functions of pipe Froude number and dimensionless plunged length of the coaxial pipe. Also, a region of existence is provided in terms of pipe Froude number and different wave types are identified. For weir flow, a nondimensional head-discharge relation is provided by analogy with overfalls