Mitigation of and adaptation to UHI phenomena : the Padua case study

Elaborating solutions to counteract UHI effects can represents a relevant challenge for spatial planning and urban design. A specific experimentation has been developed on the city of Padua, analysing different scenarios of urban warming and using specific monitoring tools (Lidar/aerial survey) to define a DIM (Digital Surface Models) providing local situation in terms of green quality and extension, solar incidence/radiation, sky view factors, building materials. This chapter reconstruct the methodology followed during the survey and the elaboration of specific solutions to counteract UHI accordingly different scenarios

Strumenti e politiche di adattamento per UHI nell\u2019area centrale veneta

La ricerca si propone di misurare l'effetto UHI sul territorio dell\u2019area metropolitana della citt\ue0 di Padova, inteso quindi come ambito \u201claboratorio\u201d per condurre approfondimenti specifici

Response surface model of a brake system to optimize structural modifications for squeal noise suppression

In spite of decades of investigation, brake squeal is still an unresolved problem. Many attempts have been made by industry and researchers to establish a general approach aimed at preventing squeal in brake design. Nowadays, the lock-in theory is one of the most accepted approaches for squeal generation and particular attention is given to the dynamics of brake systems. Moreover, one of the main difficulties encountered in studying squeal is the complexity of a real brake system. Thus many researchers approached the problem by conducting experimental and numerical analysis on simplified brake systems, and then trying to correlate the results with theoretical models. In this paper, an approach to identify appropriate changes of the physical properties of a brake system is developed, in order to suppress the squeal occurrence. First a sensitivity approach is developed to discard the less effective physical parameters. These selected parameters are those that can be modified. Subsequently, a simple mathematical model (Response Surface Model) that represents how the selected parameters affect system eigenvalues, can be obtained using Design of Experiments

Mitigazione e adattamento ai fenomeni di UHI: il caso studio di Padova

Il capitolo illustra la sperimentazione condotta e finalizzata a cogliere il legame tra clima locale, struttura urbana e formazione dell’effetto isola di calore, con l’obiettivo di orientare nel prossimo futuro, mediante linee di indirizzo, gli interventi sul territorio. E' stata qindi individuata una porzione dell’area metropolitana della città di Padova, come ambito di sperimentazione analitico-progettuale, con l’intenzione di applicare successivamente i risultati di tale sperimentazione al resto dell’area centrale veneta. Spesso le cause che generano le isole di calore urbane sono dei fattori puntuali (come ad esempio grandi super!ci pavimentate) relazionati direttamente con fattori sistemici estesi (come la dispersione notturna del calore assorbito dai tessuti urbani periferici, o l’inquinamento prodotto dalle aree produttive sempre in periferia). Questa pluralità di cause obbliga a studiare l’isola di calore a diversi livelli, sia orizzontale che verticale

Role of damping on contact instability scenarios

In the last years, many studies have been dedicated to investigate sliding contact issues between deformable bodies. Local frictional behavior and its interaction with the global dynamics of the system has been the subject of many works in several disciplines as tribology, geophysics, vibration mechanics and fracture mechanics. Experimental and numerical papers have focused the attention on the understanding how local interface dynamics (wave and rupture propagation) affects the macroscopic frictional behavior of the system during instability regime (stick-slip instability, mode coupling instability) and conversely. The stick-slip regime is characterized by sudden friction force drops (sliding state) along the time, separated by period of elastic energy accumulation (stick state). Instead, the modal dynamic instability occurs when a vibration mode of the mechanical system becomes unstable, due to frictional contact forces. This kind of instabilities, generated by frictional forces, has been mainly object of papers [5] dealing with a specific issue named brake squeal. However general and common mechanical system can generate harmonic acoustic emission comparable to brake squeal noise during relative motion with frictional contact. In such context, the role of material damping on the frictional dynamics has been investigated by a simple frictional elastic model. Comparison between nonlinear transient simulations and complex eigenvalues analysis allowed for investigating different instability scenarios for general systems in frictional contact and drawing a qualitative map in function of damping parameters. Moreover, the results show the importance on defining a good estimation of damping to modeling system with frictional contact, in order to have reliable results. Finally a brief comparison between numerical and experimental results has been carried out

Instability scenarios between elastic media under frictional contact

International audienceThis article presents the results of a numerical dynamic analysis of two bodies in sliding contact. The 2D model consists of two finite elastic media separated by a contact interface, governed by classical Coulomb friction law. The aim of this work is to investigate the instability scenarios occurring when friction forces excite the mechanical systems during the relative motion; simulation results show that the coupling between the frictional behaviour at the contact and the global dynamic of the system can bring to either stick-slip phenomena, or mode coupling instability. Complex eigenvalue analysis and transient non-linear simulations highlight how system parameters, like structural damping, affect the macroscopic frictional behaviour, switching from stick-slip phenomena to harmonic vibrations (due to mode coupling instability), up to the stable sliding state. The presented results allow for generalizing the instabilities due to mode coupling, named in brake squeal literature "lock-in" instability, to any mechanical system with frictional contact. The analyses show how maps of the instability scenarios can be drawn as a function of different parameters to help the design of systems in frictional contact

Experimental and numerical characterization of system response under dry frictional contact

The transition from macro stick-slip to continuous sliding has been observed as a function of the system parameters (boundary conditions, bi-material effect, etc.) both numerically and experimentally. The frequency and time analysis of experimental frictional phenomena exhibit good agreement with numerical results obtained through transient contact simulations as a function of the same key parameters. The numerical analysis with the support of experimental validation allow for the understanding of the physical phenomena at the origin of different frictional scenarios