Alessandro De Maio

Interplay between Shape and Roughness in Early-Stage Microcapillary Imbibition

Flows in microcapillaries and associated imbibition phenomena play a major role across a wide spectrum of practical applications, from oil recovery to inkjet printing and from absorption in porous materials and water transport in trees to biofluidic phenomena in biomedical devices. Early investigations of spontaneous imbibition in capillaries led to the observation of a universal scaling behavior, known as the Lucas-Washburn (LW) law. The LW allows abstraction of many real-life effects, such as the inertia of the fluid, irregularities in the wall geometry, and the finite density of the vacuum phase (gas or vapor) within the channel. Such simplifying assumptions set a constraint on the design of modern microfluidic devices, operating at ever-decreasing space and time scales, where the aforementioned simplifications go under serious question. Here, through a combined use of leading-edge experimental and simulation techniques, we unravel a novel interplay between global shape and nanoscopic roughness. This interplay significantly affects the early-stage energy budget, controlling front propagation in corrugated microchannels. We find that such a budget is governed by a two-scale phenomenon: The global geometry sets the conditions for small-scale structures to develop and propagate ahead of the main front. These small-scale structures probe the fine-scale details of the wall geometry (nanocorrugations), and the additional friction they experience slows the entire front. We speculate that such a two-scale mechanism may provide a fairly general scenario to account for extra dissipative phenomena occurring in capillary flows with nanocorrugated walls.

An enhanced parallel version of kiva–3v, coupled with a 1d CFD code, and its use in general purpose engine applications

Numerical simulations of reactive flows are among the most computational demanding applications in the scientific computing world. KIVA-3V, a widely used computer program for CFD, specifically tailored to engine applications, had been deeply modified in order to improve accuracy and stability, while reducing computational time. The original methods included in KIVA to solve equations of fluid dynamics had been fully replaced by new solvers, with the aim of both improving performance and writing a fully parallel code. Almost every feature of original KIVA-3V has been partially or entirely rewritten, a full 1D code has been included and a strategy to link directly 3D zones with zero dimensional models has been developed. The result is a reliable program, noticeably faster than the original KIVA-3V in serial mode and obviously even more in parallel, capable of treating more complex cases and bigger grids, with the desired level of details where required.

A Computational and Experimental Analysis for Optimization of Cell Shape in High Performance Catalytic Converters

The effects of the internal geometry of catalytic converter channels on flow characteristics; exhaust backpressure and overall conversion efficiency have been investigated by means of both numerical simulations and experimental investigations. The numerical work has been carried out by means of a micro scale numerical tool specifically tailored for flow characteristics within converter channels. The results are discussed with aid of flow distribution patterns within the single cell and backpressure figures along the catalyst channel.

A simulation model for forest fires

The control of forest fires is a very important problem for many countries around the world. Proper containment and risk management depend on the availability of reliable forecasts of the flame front propagation under the prevailing wind conditions, taking into account the terrain features and other environmental variables. In this paper we discuss our initial development of the central part of an integrated system, namely a tool to simulate the advancement of the flame front. We discuss the pyrolisis model, the wood characteristics taken into account, and the modeling of heat exchange phenomena; this modeling tool is derived from the well known fluid dynamics code Kiva, originally developed for engine design applications. Finally, we give an overview of the future directions of development for this activity, with special attention to the models of combustion employed.

FAST-EVP: an engine simulation tool

FAST-EVP is a simulation tool for internal combustion engines running on cluster platforms; it has evolved from the KIVA-3V code base, but has been extensively rewritten making use of modern linear solvers, parallel programming techniques and advanced physical models. The software is currently in use at the consulting firm NUMIDIA, and has been applied to a diverse range of test cases from industry, obtaining simulation results for complex geometries in short time frames.

Lattice Boltzmann Simulation of Diesel Injection

The evaluation and improvement of internal combustion engine performance is a challenge of major importance and it has been the object of research efforts over the last centuries. Phenomena like fuel cavitation inside diesel injector nozzles, the formation of spray and its break-up in the combustion chamber as well as the impingement of fuel droplets on engine walls are known to have a great influence on energy release during combustion and on pollutant formation and emissions, as well.In this work, a methodology based on the Lattice Boltzmann Method (LBM) is used to directly simulate phenomena affecting diesel injection. LBM is a numerical method based on Boltzmann’s Kinetic Equation, which has been successfully employed in recent years for the simulation of phenomena of technical interest.The results of LB simulations are displayed and compared to experimental data from literature, proving the accuracy of the proposed investigation method.Copyright