Silvia Di Francesco

Detailed Simulation of Complex Hydraulic Problems with Macroscopic and Mesoscopic Mathematical Methods

The numerical simulation of fast-moving fronts originating from dam or levee breaches is a challenging task for small scale engineering projects. In this work, the use of fully three-dimensional Navier-Stokes (NS) equations and lattice Boltzmann method (LBM) is proposed for testing the validity of, respectively, macroscopic and mesoscopic mathematical models. Macroscopic simulations are performed employing an open-source computational fluid dynamics (CFD) code that solves the NS combined with the volume of fluid (VOF) multiphase method to represent free-surface flows. The mesoscopic model is a front-tracking experimental variant of the LBM. In the proposed LBM the air-gas interface is represented as a surface with zero thickness that handles the passage of the density field from the light to the dense phase and vice versa. A single set of LBM equations represents the liquid phase, while the free surface is characterized by an additional variable, the liquid volume fraction. Case studies show advantages and disadvantages of the proposed LBM and NS with specific regard to the computational efficiency and accuracy in dealing with the simulation of flows through complex geometries. In particular, the validation of the model application is developed by simulating the flow propagating through a synthetic urban setting and comparing results with analytical and experimental laboratory measurements.

Application of the lattice Boltzmann method for large‐scale hydraulic problems

Purpose – The purpose of this paper is to prove the validity of the front‐tracking variant of the lattice Boltzmann method (LBM) to simulate free surface hydraulic flows (i.e. dam break flows).Design/methodology/approach – In this paper, an algorithm for free surface simulations with the LBM method is presented. The method is chosen for its computational efficiency and ability to deal with complex geometries. The LBM is combined to a surface‐tracking technique applied to a fixed Eulerian mesh in order to simulate free surface flows.Findings – The numerical method is then validated against two typical cases of environmental‐hydraulic interest (i.e. dam break) by comparing LBM results with experimental data available in literature. The results show that the model is able to reproduce the observed water levels and the wave fronts with reasonable accuracy in the whole period of the transient simulations, thus highlighting that the present method may be a promising tool for practical dam break analyses.Origina...

POROUS SUBSTRATE EFFECTS ON THERMAL FLOWS THROUGH A REV-SCALE FINITE VOLUME LATTICE BOLTZMANN MODEL

In this paper, fluid flows with enhanced heat transfer in porous channels are investigated through a stable finite volume (FV) formulation of the thermal lattice Boltzmann method (LBM). Temperature field is tracked through a double distribution function (DDF) model, while the porous media is modeled using Brinkman–Forchheimer assumptions. The method is tested against flows in channels partially filled with porous media and parametric studies are conducted to evaluate the effects of various parameters, highlighting their influence on the thermo-hydrodynamic behavior.

Optimal water distribution in a Sierpinski type network

An explicit algorithm for determining the optimal water distribution in a pipe network is applied. Supply pressure and volumetric flow requirement represent the constraints of the system. The decision parameters involved are generally design parameters (i.e., pipe diameters, pump capacities and reservoir elevations), operational parameters (i.e., pumps and valves settings), and calibration parameters (i.e., pipe roughness, node demands). The solution is obtained via a graph-theoretic approach that allows to utilize the full set of continuity and energy relations. In order to illustrate the method an application on a Sierpinski type network is presented.

A central moments model for shallow water equations: Convergence analysis

In this report we provide first results about the study of a novel central moments MRT model, in order to solve shallow water equations with Lattice Boltzmann method. The asymptotic behaviour of the viscosity and the Galilean invariance of the adopted scheme was evaluated using the test of the one-dimensional decaying wave, under the so-called diffusive scale.In this report we provide first results about the study of a novel central moments MRT model, in order to solve shallow water equations with Lattice Boltzmann method. The asymptotic behaviour of the viscosity and the Galilean invariance of the adopted scheme was evaluated using the test of the one-dimensional decaying wave, under the so-called diffusive scale.

Virtual Academic Teaching for Next Generation Engineers

Recent advances in web technology have transformed the World-Wide-Web from delivering static text to providing an easily accessible multimedia channel for dynamic, interactive communication. By using such technologies, academic teaching may evolve toward the next-generation way to transfer knowledge. At present time, there are two approaches that can be found: the Massive Open Online Courses (MOOC) approach that delivers video interactive classes to the vast audience with an open-access philosophy and Restrict-Access Courses (RAC) that deliver classes and, more important, standard degrees to limited audience [1]. While the two approaches are comparable when dealing with most academic disciplines, teaching engineering has some peculiarities that let the restricted–access course a more viable solution.First of all, engineering schools must prepare the student for the profession. In most countries, after the degree there is a professional practice period, thus a closer relation between teacher and students allows bringing the professional knowledge embedded in the academy.Being also a scientific discipline, engineering takes advantage from a close contact between teaching and research, especially for cutting-edge technologies. Finally, student projects are one of the most important steps of the educational path of the young engineers. Good student projects need one to one supervision, an adequate environment in particular for lab practice, and campuses that only restricted-access academies may provide.Copyright