1,720,974 research outputs found
Audit energetico ed ipotesi di riqualificazione di un edificio universitario
No full textL’oggetto di studio è una porzione della Facoltà di Architettura “Valle Giulia”, storicamente definita e compiuta, realizzata nel 1958 su progetto di Del Debbio come ampliamento della sede originaria degli anni ’20-‘30.
L’obiettivo della ricerca è l’individuazione di una serie gerarchica d’interventi tecnologici, impiantistici e gestionali, volti ad incrementare la qualità prestazionale ed energetica della costruzione. La ricerca può essere riassunta in tre fasi principali.
La prima fase è consistita nella caratterizzazione energetica del sistema edificio-impianto allo stato attuale. Sono state
attuate procedure volte ad acquisire informazioni sulle prestazioni degli impianti e dell’involucro edilizio. Nell'impossibilità di effettuare indagini distruttive, i dati relativi all’edificio sono stati ricavati dalle informazioni rese dalla letteratura tecnica, rielaborate attraverso la rilettura dell’organismo architettonico, lo studio delle fonti storiche e l’impiego di termografie, con le quali si sono identificate le dispersioni energetiche dovute alla presenza di radiatori, tubazioni e ponti termici. E’ stata anche effettuata una simulazione dinamica che ha permesso di valutare gli effetti del soleggiamento sull’edificio e di individuare superfici dove eventualmente installare pannelli fotovoltaici.
La seconda fase è data dalla verifica prestazionale-energetica delle proposte progettuali. Sono state analizzate e confrontate
fra loro e con lo stato attuale cinque diversi interventi. Un’analisi sperimentale sull’andamento della temperatura interna alle aule ha consentito di dimostrare la necessità di sistemi di regolazione automatica a retroazione e a compensazione per usufruire in modo razionale dell’apporto solare e degli apporti gratuiti interni.
La terza fase consiste nell’analisi costi-benefici e nella determinazione delle priorità d’intervento. I cinque interventi base e quelli dovuti alla loro combinazione sono stati confrontati con lo stato attuale rapportando i benefici energetici e gli investimenti necessari a realizzarli, ottenendo una serie di informazioni che evidenzia le soluzioni più efficaci
Analisi comparata di interventi di riqualificazione energetica per la Facoltà di architettura di Roma “Valle Giulia” Energy saving potential for the Faculty of Architecture "Valle Giulia" in Rome
No full textL’oggetto di studio è rappresentato da una porzione della Facoltà di Architettura “Valle Giulia”, storicamente definita e compiuta, realizzata nel 1958 su progetto di Del Debbio come ampliamento della sede originaria degli anni ’20.
L’obiettivo della ricerca è individuare una serie gerarchica d’interventi tecnologici, impiantistici e gestionali, volti ad incrementare la qualità prestazionale ed energetica della costruzione, attraverso tre fasi principali.
La prima fase è rappresentata dalla caratterizzazione energetica del sistema edificio-impianto allo stato attuale, con procedure volte ad acquisire informazioni sulle prestazioni degli impianti e dell’involucro edilizio. Nell’impossibilità di attuare indagini distruttive, i dati relativi all’edificio sono stati ricavati dalle informazioni rese dalla letteratura tecnica e rielaborate attraverso una rilettura dell’organismo architettonico, uno studio accurato delle fonti storiche, l’impiego di termografie.
La seconda fase è costituita dalla verifica prestazionale-energetica di alcune proposte progettuali, sulla porzione opaca e su quella trasparente dell’involucro, sui sistemi impiantistici. Un’analisi sperimentale sull’andamento della temperatura interna alle aule ha consentito di dimostrare la necessità di sistemi di regolazione automatica per usufruire in modo razionale dell’apporto solare e degli apporti gratuiti interni.
La terza fase comprende un’analisi costi-benefici con determinazione delle priorità d’intervento. Gli interventi base attuati singolarmente o combinati sono stati confrontati con lo stato attuale, rapportando i benefici energetici e gli investimenti necessari a realizzarli, ottenendo una serie degli interventi che evidenzia quelli più efficaci
FLEW: a DNS Solver for compressible flows in generalized curvilinear coordinates
Full text linkWe present FLEW, an in-house high-fidelity solver for direct numerical simulation (DNS) of turbulent compressible flows
over arbitrary shaped geometries. FLEW solves the Navier–Stokes equations written in a generalized curvilinear coordinate
system, in which the surface coordinates are non-orthogonal, whereas the third axis is normal to the surface. Spatial dis-
cretization relies on high-order finite-difference schemes. The convective terms are discretized using an hybrid approach,
combining the near-zero numerical dissipation provided by central approximations with the robustness of weighted essentially
non-oscillatory (WENO) schemes, required to capture shock waves. Central schemes are stabilized using a skew-symmetric-
like splitting of convective derivatives, endowing the solver with the energy-preserving property in the inviscid limit. The
maximum order of accuracy is eighth for central schemes (also used for viscous terms discretization) and seventh for WENO.
The code is oriented to modern high-performance computing (HPC) platforms thanks to message passing interface (MPI)
parallelization and the ability to run on graphics processing unit (GPU) architectures. Reliability, accuracy and robustness of
the code are assessed in the low-subsonic, transonic and supersonic regimes. We present the results of several benchmarks,
namely the inviscid Taylor–Green vortex, turbulent curved channel flow, transonic laminar flow over a NACA 0012 airfoil and
turbulent supersonic ramp flow. The results for all configurations proved to be in excellent agreement with previous studies
Interventi di riqualificazione, un'analisi comparata
No full textValutazione energetica ed economica di interventi per la riduzione dei consumi della Facoltà di Architettura di Roma "Valle Giulia"
Direct numerical simulation of drag reduction in rotating pipe flow up to Reτ ≈ 3000
No full textDirect numerical simulation (DNS) of rotating pipe flows up to Reτ ≈ 3000 is carried
out to investigate drag reduction effects associated with axial rotation, extending previous
studies carried out at a modest Reynolds number (Orlandi & Fatica, J. Fluid Mech.,
vol. 343, 1997, pp. 43–72; Orlandi & Ebstein, Intl J. Heat Fluid Flow, vol. 21, 2000,
pp. 499–505). The results show that the drag reduction, which we theoretically show
to be equivalent to net power saving assuming no mechanical losses, monotonically
increases as either the Reynolds number or the rotation number increases, proportionally
to the inner-scaled rotational speed. Net drag reduction up to approximately 70 % is
observed, while being far from flow relaminarisation. Scaling laws for the mean axial
and azimuthal velocity are proposed, from which a predictive formula for the friction
factor is derived. The formula can correctly represent the dependency of the friction factor
on the Reynolds and rotation numbers, maintaining good accuracy for low-to-moderate
rotation numbers. Examination of the turbulent structures highlights the role of rotation in
widening and elongating the small-scale streaks, with subsequent suppression of sweeps
and ejections. In the core part of the flow, clear weakening of large-scale turbulent motions
is observed at high Reynolds numbers, with subsequent suppression of the outer-layer peak
in the pre-multiplied spectra. The Fukagata–Iwamoto–Kasagi decomposition indicates
that, consistent with a theoretically derived formula, the outer layer yields the largest
contribution to drag reduction at increasingly high Reynolds numbers. In contrast, both the
inner and the outer layers contribute to drag reduction as the rotation number increases
On low-frequency unsteadiness in swept shock wave–boundary layer interactions
Full text linkWe derive a scaling law for the characteristic frequencies of wall pressure fluctuations
in swept shock wave/turbulent boundary layer interactions in the presence of cylindrical
symmetry, based on analysis of a direct numerical simulations database. Direct numerical
simulations in large domains show evidence of spanwise rippling of the separation line,
with typical wavelength proportional to separation bubble size. Pressure disturbances
around the separation line are shown to be convected at a phase speed proportional
to the cross-flow velocity. This information is leveraged to derive a simple model for
low-frequency unsteadiness, which extends previous two-dimensional models (Piponniau
et al., J. Fluid Mech., vol. 629, 2009, pp. 87–108), and which correctly predicts growth of
the typical frequency with the sweep angle. Inferences regarding the typical frequencies in
more general swept shock wave/turbulent boundary layer interactions are also discussed
Development of a dns solver for compressible flows in generalized curvilinear coordinates
No full textWe present a solver for DNS of turbulent compressible flows over arbitrary shaped
geometries. The code solves the compressible Navier-Stokes equations in a generalized curvilinear
coordinates system, using high-order central finite-difference schemes combined with WENO
reconstruction for shock-waves treatment. An innovative stabilization strategy for central schemes
based on skew-symmetric-like splitting of convective derivatives is used. The code is oriented to
modern HPC platforms thanks to MPI parallelization and the ability to run on GPU architectures.
The robustness and accuracy of the present code is assessed both in the low-subsonic case and in
the supersonic case. We show here the results of a turbulent curved channel flow and a turbulent
supersonic compression ramp, which proved to be in excellent match with previous studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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