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Indoor-outdoor pollutant transport through a hollow cube with a cross-ventilating flow
No full textCross-ventilation plays a critical role in dispersing indoor pollutants by promoting the exchange of indoor and outdoor air. To investigate pollutant transport in such scenarios, we experimentally investigate the flow through a hollow cube immersed in an atmospheric boundary layer as an idealized representation, with a ground-level passive scalar (pollutant) source placed at the centre of the building. The focus is on characterizing the velocity and concentration fields to understand the scalar transport mechanisms within and outside the cube. Two different experiments are conducted comparing results from the University of Surrey EnFlo wind tunnel and the University of Southampton water tunnel. The wind tunnel experiments used a laser Doppler anemometer (LDA) and a Fast flame ionization detector (FFID) to collect point measurements of the velocity and concentration, respectively. The water tunnel experiments used Planar Laser-Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV) to obtain simultaneous measurements of scalar and flow fields. The insights gained from this study can potentially improve our understanding and help model pollutant exchange between indoor and outdoor environments, especially in complex atmospheric boundary layer condition
Passive scalar transport in a cross-ventilating flow with upstream source: wind and water tunnel measurements
No full textIn urban environments, pollutant ingress from outdoor sources poses a significant challenge to indoor air quality. Cross-ventilation, while essential for passive cooling and natural airflow, can also facilitate the entry of outdoor contaminants into indoor spaces. To investigate the dynamics of outdoor-to-indoor pollutant transport, the present study employs an idealized configuration, namely, a hollow cube representing a scaled-down model building with window openings in the upstream and downstream faces, subjected to an upstream passive scalar source within an atmospheric boundary layer. The experiments are conducted in two distinct facilities: a water tunnel using Rhodamine dye as the scalar, and a wind tunnel using propane gas, all performed at a specified flow Reynolds number of Re=URefH/v ≈ 50,000 for a fixed boundary layer-to-cube height ratio of about 3; here, is the streamwise velocity at cube’s height (H) measured without the cube. The scalar, released from a ground-level upstream source, is predominantly transported by a streamwise advective flux, while relatively weaker wall-normal advective and turbulent fluxes contribute to vertical dispersion and local mixing. A fraction of the oncoming scalar enters the cube intermittently, through the upstream window. Inside, a central jet-like flow carries the scalar parcels primarily by streamwise advective flux, while also interacting with the upper and lower recirculation regions, enabling scalar exchange across these zones through wall-normal advective and turbulent fluxes. While the time-averaged concentration field inside the cube is nearly uniform, suggesting effective mixing, instantaneous concentration traces exhibit strong intermittency, with sporadic peak events, highlighting the risk of transient peak exposures. The indoor concentration exponentially decays over time once the source is turned off, with a slower decay in the upper recirculation region, implying relatively prolonged exposure near the ceiling region. Both experimental setups produce closely matching values and consistent trends in the spatio-temporal dynamics of scalar concentration, and also highlight their complementary nature, with each offering distinct advantages. The present findings will deepen our understanding of pollutant ingress and mixing in buildings in cross-ventilated flows and also offer valuable insights to future modeling of pollutant exposure in urban indoor spaces
Pollutant dispersion in a cross-ventilating flow through a scaled building : Wind and water measurements
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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
Scalar fluxes near a tall building in an aligned array of rectangular buildings
No full textScalar dispersion from ground level sources in arrays of buildings is investigated using wind-tunnel measurements and large eddy simulation (LES). An array of uniform height buildings of equal dimensions and an array with an additional single tall building (wind tunnel) or a periodically repeated tall building (LES) are considered. The buildings in the array are aligned and form long streets. Sensitivity of the dispersion pattern to small changes of wind direction is demonstrated. Vertical scalar fluxes are decomposed into the advective and turbulent parts and the influences of wind direction and of the presence of the tall building on scalar flux components are evaluated. In the uniform height array turbulent scalar fluxes were dominant, whereas the tall building causes increase of the magnitude of advective scalar fluxes which become the largest component
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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