Foto del docente

Vittorio Di Federico

Full Professor

Department of Civil, Chemical, Environmental, and Materials Engineering

Academic discipline: ICAR/01 Hydraulics


Keywords: environmental hydraulics probabilistic risk analysis gravity currents polynomial chaos expansion fractured media groundwater water distribution and sewer systems stochastic approach heterogeneity non-Newtonian fluids porous media fluid mechanics

1)    Groundwater hydrology and hydraulics:

 1a) Model reduction and uncertainty quantification;

 1b) Characterization of heterogeneity, scaling, flow and transport in porous and fractured media;

 1c) Nonlinear (Forchheimer and non-Newtonian) flows;

 1d) Subsurface heat transfer and geothermal devices;

 1e) Seawater intrusion;

 1f) Probabilistic risk assessment (PRA).

 2)   Environmental Fluid Mechanics and Hydraulics:

 2a) Free-surface debris and hyperconcentrated flow.

 2b) Geophysical gravity and density currents in viscous and inertial regime;

 2c) Fluvial hydraulics and morphodynamics.

 3)   Urban hydraulics:

 3a)  Analysis of pipe failure data;

 3b) Reliability analysis of water distribution and sewer systems;

 3c) Life Cycle Assessment (LCA);

 3d) Decision Support Systems (DSS);

 3e) Risk-based asset management.

1) Groundwater hydrology and hydraulics:

 1a) Model reduction and uncertainty quantification. Stochastic differential equations describing the behavior of complex environmental systems are analyzed, together with techniques for their reduction (surrogate models). For complex environmental problems under uncertainty, Global Sensitivity analysis (GSA) is employed, via the adoption of computationally efficient Polynomial Chaos Expansion methods.

 1b) Characterization of heterogeneity, scaling, flow and transport in porous and fractured media. Heterogeneity in geologic porous media is investigated via geostatistical methods. Scaling of hydraulic conductivity and solute dispersivity si investigated within a unified multiscale conceptual framework which views hydraulic conductivity as a random fractal field. Several problems in stochastic groundwater hydraulics (uniform flow, radial flow towards wells, solute transport, conditioning with field measurements) have been examined adopting the former theory, employing analytical and/or numerical methods. Methods adopted for the description of flow and transport are analytical and numerical (small perturbations, Monte Carlo simulations and moment equations).

 1c) Nonlinear (Forchheimer and non-Newtonian) flows in porous and fractured media. Flow and transport in porous media and fractures is examined when the relationship between flux and pressure gradient is nonlinear, either due to exceedance of the Darcy threshold, or due to the non-Newtonian nature of the fluid . The research aims at a detailed understanding of flow and transport phenomena at the pore or single fracture scale, and at developing simplified methodologies and representative parameters for larger scales.

 1d) Subsurface heat transfer and geothermics. The thermal efficiency of novel shapes of ground heat exchangers (GHEs) employed in geothermal closed loops is tested by solving the transient flow and heat transport problem within the surrounding ground via analytical and numerical models. The aim is to optimize the shape of the exchanger while minimizing the thermal impact on the soil, and to evaluate the effect on parameter uncertainty on model response.

 1e) Seawater intrusion. The influence of parameter uncertainty on seawater intrusion in coastal phreatic or confined aquifers is investigated re-examining existing analytical models under the viewpoint of risk analysis. Model sensitivity to random input parameters is assessed by means of the PCE technique, to evaluate the probability of a variety of undesired events (e.g. well or sensitive area contamination). Data-driven techniques relying on various statistical regressive and auto-regressive models are employed for real cases in which analytical models are not applicable, such as the Emila Romagna phreatic aquifer.

 1f) Probabilistic risk assessment (PRA). After an in-depth analysis of existing literature on risk analysis in natural systems (including methodologies such as “fault tree” and “event tree” analysis), the aim is to develop a integrated framework for risk evaluation, including: i) risk analysis, with identification of risk factors and their quantitative evaluation; ii) risk assessment; iii) risk reduction and control, including the definition and implementation of a decisional process and monitoring. The methods thus individuated, essentially of a probabilistic nature, are applied to aquifers, to support controlled exploitation of groundwater resources and treatment of contaminated sites, of much interest nowadays in connection with the recovery of industrial areas located within the urban perimeter; specifically, for complex environmental problems under uncertainty, Gobal Sensitivity analysis (GSA) is employed, via the adoption of Polynomial Chaos Expansion methods.

 2) Environmental Fluid Mechanics and Hydraulics:

 2a) Free-surface debris and hyperconcentrated flow. Free-surface flow of non-Newtonian fluids is studied in laminar and turbulent regime, with different geometries and boundary conditions. The impact of different rheological equations on integrated variables such as the flowrate is examined. The research aims at a deeper understanding of debris flow phenomena and mining sludges behavior.

 2b) Geophysical viscous and inviscid gravity and density currents. Several important phenomena in industrial, geophysical and environmental applications involve the relative flow of two fluids due to a density difference. Such phenomena are studied in different geometries, for free-surface or porous media flow, and for Newtonian and non-Newtonian fluids, the latter with a variety of constitutive laws. The possible propagation regimes (viscous or inertial) is investigated, pursuing first an analytical approach and then a numerical solution. Space-time development of gravity currents is investigated for different values of rheological parameters. The experimental validation of theories is pursued with laboratory experiments. The influence of medium heterogeneity for gravity currents in porous media is examined with a deterministic or stochastic approach.

 2c) Fluvial hydraulics and morphodynamics. The study deals with calibration of a 2-D morphodynamic model of a stretch of the Po River (Italy) using detailed measurements of the river's morphology and water-sediment fluxes derived from an ADCP recording. Sensitivity analyses are performed to analyze the effects of bed roughness and sediment transport direction on the simulated flow field and morphology.

 3) Urban hydraulics:

 3a) Pipe break data analysis. A statistical analysis of break/blockage events in water/drainage networks is performed, with the aim of defining prediction formulae.

 3b) Reliability analysis of water distribution and sewer systems. For water supply system, the research aims at deriving innovative indices for nodal and overall network performance. For sewer systems, the research aim is the description of hydraulic and environmental performance of drainage systems both in the present condition and in possible future scenarios considering sewer system temporal decline and the application of feasible rehabilitation techniques.

 3c) Life Cycle Assessment (LCA). The Life Cycle Energy Analysis (LCEA) methodology is applied to water distribution networks, allowing to identify the most convenient scenarios in terms of energy cost, materials choice, technologies, and maintenance strategies. The final aim is to provide a decision support system coupling the energy saving and reduction of environmental impact viewpoints to reliability, risk and cost dimensions. A pipe lifecycle is subdivided into three phases: fabrication, use and life end. For each phase, the energy cost associated to each functional unit is evaluated by means of a novel theoretical approach, modifying earlier literature findings.

 3d) Decision Support Systems (DSS). The research aim is to establish a rational framework for water supply systems and sewer network rehabilitation decision making, developing intermediate tools/products and a Decision Support System (DSS) enabling municipal engineers to establish and maintain effective management of their water supply and sewer networks with a pro-active approach.

 3e) Risk-based Asset management. Sustainable asset management of water supply systems, sanitary and drainage network will be pursued under the triple bottom line approach of economic, social and environmental aspects. Performance indicators to evaluate sustainability are developed at different scales. These indicators are evaluated via the urban methabolism model, which views the integrated water cycle as a living organism, whose different parts exchange mass and energy fluxes.