1,721,140 research outputs found
Multi-disciplinary, community-oriented design of low-noise aircraft: the COSMA project
No full textThe EC-funded project COSMA (Community Oriented
Solutions to Minimize aircraft noise Annoyance, 7th
Framework Programme) started in June 2009 with an ambitious,
twofold goal: improve the understanding of the
annoyance induced by aircraft noise on the population
and identify the engineering guidelines to establish appropriate
design strategies and operational procedure to reduce
these effects. The project was conceived within the
context of the X-Noise Collaborative Network, a worldwide
network of experts and institutions committed to the
commercial aviation noise challenge. The COSMA objectives
were addressed using a highly multi-disciplinary approach,
integrating competences pertaining to psychoacoustics,
sound engineering, and aeronautical engineering.
The work of twenty-three research groups from nine
European countries was structured in six, strongly interconnected
work packages. Aim of the present paper is the
review of this cross-disciplinary research from the point
of view of the aircraft designer. The attention is focused
on the Optimisation of Airport Noise Scenarios work package,
where the aeronautical technology contextwas established
in detail and where, eventually, the design criteria
and operational recommendation were defined on the basis
of the outcomes of the annoyance examination experimental
campaign
On the use of a SIMD vector extension for the fast evaluation of Boundary Element Method coefficients
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An aeroelastic approach to the numerical simulation of a reed-driven woodwind musical instrument
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Elementi di meccanica razionale
No full textQuesto libro presenta la trattazione teorica dei temi fondamentali della Meccanica Razionale. Gli argomenti discussi, la loro sequenza, la simbologia utilizzata e la modalità di sviluppo della teoria attraverso cui si giunge alla definizione dei modelli matematici utili alla soluzione dei problemi della Meccanica Razionale sono quelli ritenuti dagli autori più idonei per allievi ingegneri che frequentano un corso di laurea triennale di indirizzo industriale. Partendo dai richiami sull’Algebra vettoriale e la Dinamica del punto materiale, il testo prosegue con lo studio dei Sistemi particellari che risulta essere anche propedeutico per gli argomenti trattati nei successivi capitoli. Quindi si esaminano i temi della Cinematica del corpo rigido, per poi arrivare allo studio dei Moti relativi per l’introduzione dei sistemi di riferimento non inerziali, e allo sviluppo dei modelli matematici per la Dinamica del corpo rigido. Un capitolo viene dedicato agli elementi della Meccanica lagrangiana
Theoretical and Numerical Modeling of Acoustic Metamaterials for Aeroacoustic Applications
No full textThe advent, during the first decade of the 21st century, of the concept of acoustic metamaterial has disclosed an incredible potential of development for breakthrough technologies. Unfortunately, the extension of the same concepts to aeroacoustics has turned out to be not a trivial task, because of the different structure of the governing equations, characterized by the presence of the background aerodynamic convection. Some of the approaches recently introduced to circumvent the problem are biased by a fundamental assumption that makes the actual realization of devices extremely unlikely: the metamaterial should guarantee an adapted background aerodynamic convection in order to modify suitably the acoustic field and obtain the desired effect, thus implying the porosity of the cloaking device. In the present paper, we propose an interpretation of the metamaterial design that removes this unlikely assumption, focusing on the identification of an aerodynamically-impermeable metamaterial capable of reproducing the surface impedance profile required to achieve the desired scattering abatement. The attention is focused on a moving obstacle impinged by an acoustic perturbation induced by a co-moving source. The problem is written in a frame of reference rigidly connected to the moving object to couple the convective wave equation in the hosting medium with the inertially-anisotropic wave operator within the cloak. The problem is recast in an integral form and numerically solved through a boundary-field element method. The matching of the local wave vector is used to derive a convective design of the metamaterial applicable to the specific problem analyzed. Preliminary numerical results obtained under the simplifying assumption of a uniform aerodynamic flow reveal a considerable enhancement of the masking capability of the convected design. The numerical method developed shows a remarkable computational efficiency, completing a simulation of the entire field in a few minutes on mid-end workstations. The results are re-interpreted in term of boundary impedance, assuming a locally-reacting behavior of the outer boundary of the cloaking layer. The formulation is currently being extended to the analysis of arbitrarily complex external flows in order to remove the limitation of the background uniform stream in the host
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