Roberta Padulano

Combined Effects of Parallel and Series Detention Basins for Flood Peak Reduction

A simple analytical method is proposed that allows a preliminary evaluation of the overall efficiency of a detention basin system for flood risk reduction in a specific target section. Solutions are provided both for parallel and series systems, under some simplifying assumptions concerning the linearity of detention basin, river network and watershed responses. Further, for the series configuration a regressive model is proposed for the computation of the overall efficiency, because of the complexity of analytical solution. A case study is also presented, where the overall efficiency of a system of nine detention basins is computed by means of both the analytical and the regressive model. Results are discussed to assess the different influence of detention basins in parallel or in a series system.

Optimization of Osmotic Desalination Plants for Water Supply Networks

Water scarcity and the poor quality of water resources are leading to a wider diffusion of desalination plants using the Reverse Osmosis (RO) process. Unfortunately, the cost of a cubic meter of fresh water produced by an RO plants is still high and many efforts are in progress to increase the efficiency of the membranes used in osmotic plants and to limit the energy required by the process. A further reduction of the energy cost could be obtained by an optimal operation of the desalination plant so reducing the hourly energy cost, or by coupling the RO plant with an energy production plant based on direct osmosis (Pressure Retarded Osmosis PRO).The economic viability of the desalination process has been analyzed until now without accounting for the integration of the RO plant with the existing water network. This analysis is developed in the present paper with reference to a hypothetical change of water supply in a real network, where a desalination plant is used to satisfy the fresh water demand. Several scenarios will be analyzed to assess the minimum cost of fresh water production and water supply to the network, including the use of energy recovery systems, such as an integrated use of RO and PRO processes, or the regulation of pressure at the network intake by a micro hydro power plant.

Multivariate probability distribution for sewer system vulnerability assessment under data-limited conditions

The lack of geometrical and hydraulic information about sewer networks often excludes the adoption of in-deep modeling tools to obtain prioritization strategies for funds management. The present paper describes a novel statistical procedure for defining the prioritization scheme for preventive maintenance strategies based on a small sample of failure data collected by the Sewer Office of the Municipality of Naples (IT). Novelty issues involve, among others, considering sewer parameters as continuous statistical variables and accounting for their interdependences. After a statistical analysis of maintenance interventions, the most important available factors affecting the process are selected and their mutual correlations identified. Then, after a Box-Cox transformation of the original variables, a methodology is provided for the evaluation of a vulnerability map of the sewer network by adopting a joint multivariate normal distribution with different parameter sets. The goodness-of-fit is eventually tested for each distribution by means of a multivariate plotting position. The developed methodology is expected to assist municipal engineers in identifying critical sewers, prioritizing sewer inspections in order to fulfill rehabilitation requirements.

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.

Novel Diversion Structure for Supercritical Flow

AbstractIn urban drainage systems, it is usually necessary to split the storm water discharge among different sewer branches because of limited flow capacity of either hydraulic structures or sewer lines. For this purpose, sewer sideweirs and leaping weirs are generally used as diversion overflow structures. For supercritical approach flow, the former is not recommended because of the occurrence of hydraulic jumps, whereas the latter requires an outlet located below the approach flow sewer bottom. To overcome these constraints, a novel compact hydraulic structure is proposed. It consists of a frontal rectangular intake, representing the diversion sewer inlet, located in the approach flow sewer and parallel to its bottom. A 6.67:1 scale model was tested over a range of hydraulic and geometrical parameters to determine its head-discharge relationship, developing a dimensionless equation relating the diversion discharge to the geometrical properties of the intake under supercritical flow conditions. The limi...

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. been studied by several researchers. Ohtsu et al. (1991) and Hager and Li (1992) described the effect of a continuous end sill on the hydraulic jump, while Habibzadeh et al. (2011) studied the dissipation efficiency of baffle blocks when a submerged jump occurs. This paper describes the experimental campaign performed on the physical model of Lower Diamphwe Dam (Malawi), which is provided with an uncontrolled spillway and a USBR type II stilling basin. The USBR type II basin is provided with blocks at the end of the chute and a dentated sill at the end of the basin (Fig. 1). The aim of the paper consists in the study of its hydraulic behavior, which has been poorly investigated so far, to the Authors’ knowledge. Measurements of pressure fluctuation upstream and downstream of the dentated sill were

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

AbstractAn 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-discha...

Hydraulic Design of a USBR Type II Stilling Basin

AbstractThe 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 ...

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.