Renata Della Morte

Stochastic approaches for sensors placement against intentional contaminations in water distribution systems

Water distribution systems are vulnerable to intentional contamination: in this paper, optimising the placement of a set of monitoring stations to promptly detect this type of attack is considered. Due to the uncertainty about the place and the time of the beginning of the attack, and the inherent variability of the hydraulic conditions throughout the water distribution network, the impact probability distribution (IPD) has been defined in order to take into account the random variability of the conventional measures of impact. Two different approaches for the optimal placement of the monitoring stations are compared: the first minimises the expected value of a conventional damage measure, while the second minimises a given percentile of the IPD. The two approaches are applied to a real-world case study, showing their feasibility.

Optimal Location and Setting of PRVs in WDS for Leakage Minimization

Water loss is an issue that affect Water Distribution Systems (WDSs) very often, especially when aged and high pressure occurs. Pressure reduction valves (PRVs) can be used as devices to reduce as much as possible the water losses within the network. Indeed, for a given number of PRVs, the daily volume of water lost from the network can be reduced minimizing the pressure through a proper choice of valve positions as well as their settings. In this paper, a methodology for the optimal number, positioning and setting of PRVs is presented. In the proposed methodology, a genetic algorithm is coupled with a physical modelling of leakage from joints and a simplified and yet realistic hydraulic simulation of the WDS. The proposed methodology is demonstrated using two WDSs examples. Comparisons with a more extreme and complicated hydraulic modelling, already proposed by authors in previous work, are also performed in the first case study in order to validate the proposed methodology. These comparisons demonstrate that the methodology proposed in this work performs fairly well when compared to similar approach that uses a more sophisticated hydraulic model. As a consequence, it revealed to be a good tool for the optimal positioning and sizing of PRVs within WDS aimed at reducing the background leakages even when the WDS is characterized by complex geometry and topology.

Enhancing the Efficiency of the Automatic Design of Rural Drainage Networks

AbstractThe discharges flowing through rural drainage networks depend not only on the local climatic and hydrologic characteristics, but also on the geometric characteristics of the channels constituting the network. For this reason, the evaluation of the design discharges should be accomplished during the search of the optimal network. This leads to time-consuming optimization procedures, and it is desirable to devise efficient numerical alternatives. Two novel models, EGA and EGA-f, are proposed in order to increase the numerical efficiency of genetic algorithms (GAs) for the solution of the optimal rural drainage network problem. Both EGA and EGA-f procedures are based on the use of the nodal excavation depths at the channel ends as decision variables. Moreover, the EGA-f procedure improves EGA by freezing temporarily the design discharges during the optimization process in the case where uniform flows through the channels can be assumed. The application of the two models is demonstrated by means of nu...

Novel Numerical Approach for 1D Variable Density Shallow Flows over Uneven Rigid and Erodible Beds

AbstractThe numerical modeling of hyperconcentrated shallow flows is a challenging task because they exhibit special features, such as propagation over dry beds, profound bed elevation modifications owing to erosion or deposition phenomena, and flow discontinuities. In this paper, a novel depth-positivity preserving Harten, Lax, and van Leer—contact (HLLC) Riemann solver is devised in order to approximate the solution of the Riemann problem for the 1D (one-dimensional) hyperconcentrated shallow flows equations over horizontal beds. The solver is used as a building block for the construction of hyperconcentrated shallow flows (HCSF), a well-balanced finite-volume scheme for the solution of the hyperconcentrated shallow flows equations with variable elevation. HCSF is able to handle the case of dry beds, to take into account the variability of the topography also in the presence of bed discontinuities, considering the flow resistance and the mass exchange between the flowing mixture and the mobile bed. The ...

A numerical model for the simulation of debris flow triggering, propagation and arrest

In this paper, it is described the development and the assessment of a 1D numerical procedure for the simulation of debris flow phenomena. The procedure focuses on: (1) the rainfall triggering, and the effects induced on slope stability by both rainfall infiltration and groundwater dynamics; (2) the possible inception of debris flows during the propagation phenomenon itself, due to the actions exerted on the slope by the already triggered flowing masses; (3) the propagation phenomenon over complex topographies; (4) the non-Newtonian internal dissipative processes that develop within the sediment–water mixture; (5) the effects induced by the evolution of the boundaries where the propagation phenomenon occurs; (6) the run-out and arrest phenomena. In order to show the performance and capabilities of the model, the results of its application to an analytic test and to laboratory experimental tests are first analyzed, and finally, the application to a plausible debris flow scenario, taken from a real case study, is discussed.

Exact Solution of the Dam-Break Problem for Constrictions and Obstructions in Constant Width Rectangular Channels

AbstractIn hydraulic engineering, it is common to find geometric transitions where a channel is not prismatic. Among these geometric transitions, constrictions and obstructions are channel reaches ...

Supercritical low-crested bilateral weirs: hydraulics and design procedure

Sideweirs are hydraulic structures commonly used in combined sewer systems for separating excess storm water from urban sewage. In the case of low-crested sideweirs, the design is difficult because supercritical flows may establish along the overflow reach. This can lead to transcritical conditions not easily modelled in many cases. The present paper analyses the supercritical outflow process over a low-crested bilateral sideweir in a circular channel, based on both experimental and numerical investigations. Experiments were conducted to define the approach water depth and the free-surface profiles. The measurements were compared with the numerical values resulting from the application of energy and momentum conservation principles. The paper shows that the formulas used for estimating the end depth at free overfalls in circular channels can be applied to evaluate the approach water. The numerical investigation proves that the energy conservation approach allows for the computation of free-surface profiles with reasonable accuracy.

A new frequency domain analytical solution of a cascade of diffusive channels for flood routing: FREQUENCY DOMAIN ANALYTICAL SOLUTION FOR FLOOD ROUTING

Simplified flood propagation models are often employed in practical applications for hydraulic and hydrologic analyses. In this paper, we present a new numerical method for the solution of the Linear Parabolic Approximation (LPA) of the De Saint Venant equations (DSVEs), accounting for the space variation of model parameters and the imposition of appropriate downstream boundary conditions. The new model is based on the analytical solution of a cascade of linear diffusive channels in the Laplace Transform domain. The time domain solutions are obtained using a Fourier series approximation of the Laplace Inversion formula. The new Inverse Laplace Transform Diffusive Flood Routing model (ILTDFR) can be used as a building block for the construction of real-time flood forecasting models or in optimization models, because it is unconditionally stable and allows fast and fairly precise computation.