1,720,972 research outputs found
Urban ventilation and the compact Mediterranean city numerical analysis of the dynamic relationships between density, morphology, and wind flow
Full text linkCombining urbanization and climate change provides new and complex challenges to our cities since they represent a vulnerable element at the center of human life. Cities have been regarded as the emblem of scientific and technological progress, health, and wealth for centuries by humankind. They have gradually attracted the majority of the world population and economic activities. In this process, cities increased in number, size, and density, leading to gradual and inexorable environmental and social degradation. Consequently, the challenge towards more sustainable and resilient built environments has become urgent, especially in existing cities. In this framework, investigations of wind flow in the urban environment are of primary importance. They involve various topics and associated processes, such as human health and comfort, energy consumption and production, durability and robustness of materials, buildings, and infrastructures. Weak wind conditions, often experienced in compact urban areas, can be responsible for low air quality, hence higher potentially hazardous air pollution levels, and higher temperatures, thus increased amplification of heatwaves and human thermal stress. These phenomena cause augmented morbidity, mortality, and energy demand for air cooling and purification. The detrimental effects of air pollution and heat stress on human health and comfort may be mitigated by exploiting urban ventilation.
Urban ventilation represents the capacity of a built area for introducing fresh air within its tissue and diluting pollutants and heat within its canyons. The phenomenon is closely related to urban morphology, i.e., the form and the structure of the urban area, the physical characteristics of the buildings, and their mutual arrangement. Conversely, urban morphology can be an effective tool in renewal plans for improving urban ventilation in urban areas. For this purpose, detailed investigations of the impact of actual urban morphologies on urban ventilation are fundamental and represent an essential step towards more sustainable and resilient cities, especially in the Mediterranean area, where a continuous increase in the mean air temperature can already be observed. However, given the complexity of the phenomena in play, the majority of these studies used simplified models of actual urban areas, i.e., arrangements of generic building geometries forming idealized urban structures. Albeit useful, these simplified models may not reproduce the complexity of the built environment.
In this regard, the main objective of the present research is to identify and validate a methodology for analyzing the effects of urban density and morphology on urban ventilation performance in actual urban areas. The research is structured in three main phases. The first phase involves describing and quantifying the physical structure of urban areas. The second phase covers the investigation of wind flows at the relevant observation scale for the selected case study. The final phase regards the correlation of the results of the analyses performed during the previous two stages.
In the first stage, through an extensive literature review, indices used by practitioners and city planners are selected to describe and quantify the densities and morphologies of different urban tissues. The district scale is used as the operational scale to perform morphological analyses because it is suitable to describe the morphological characteristics of urban areas. The Tuscolano-Don Bosco district, an area in the Southeast of Rome, is selected as the case study. The district presents morpho-typological features typical of compact cities in the Mediterranean basin. Morphological analyses are conducted for the selected area using GIS software, and several scripts and algorithms have been used to combine the raw data to calculate the morphological parameters. In the second stage, appropriate tools, techniques, and indicators for investigating wind flows and assessing urban ventilation performance at the district scale in actual urban areas are selected. Then, 3D steady-state RANS simulations are performed for 12 different wind directions to investigate the impact of different urban morphologies on wind flows and urban ventilation in the selected area. The validation of the computational setting is performed using experimental data from wind-tunnel measurements found in literature and conducted for an idealized case study with physical features similar to the actual case study, applying the so-called sub-configuration approach. The results are presented in terms of non-dimensional mean wind velocity and local age of air, i.e., the time a particle of external fresh air spends replacing a particle of the pollutant in a specific location within the area of interest. The abovementioned parameters and their derivatives are employed in the research as key performance indicators for urban ventilation. In the third stage, the wind environment in the entire case study is described and analyzed. The non-dimensional mean wind velocity calculated at two different heights is correlated to the selected morphological parameters to provide linear, easy-to-use models for highlighting areas potentially vulnerable to poor air conditions without running computationally expensive simulations. Finally, the key performance indicators are used to assess the effectiveness of the different morphologies within the case study in enhancing urban ventilation.
The results show that, in a compact urban area, a drastic reduction in the mean wind velocity, up to 60%, can be experienced at the pedestrian level with a consequent worsening of thermal comfort conditions and air quality. The mean wind velocity reduction is dependent on the urban density and increases monotonically with increases in the morphological parameters. Moreover, the linear models between urban ventilation indicators and morphological parameters show remarkable correlations: coefficients of determination up to 89%. Furthermore, results demonstrate that specific morphologies depending on the wind direction can determine locally pronounced increases in the mean wind velocity, up to 135%, and enhance urban ventilation. The research results confirm the potential of urban morphology in enhancing urban ventilation and the need for approaching regeneration plans according to a climate-sensitive/climate-aware way since sustainability and resilience are the ultimate goals.
This research contributes to establishing a knowledge base of the wind environment in compact cities and developing guidelines for prioritizing regeneration plans in existing urban areas. This work represents a further step to integrate different disciplines to ease the management of the urban environment complexity. The research outcomes are of interest to stakeholders, practitioners, policymakers, and researchers
Urban Ventilation in the Compact City: A Critical Review and a Multidisciplinary Methodology for Improving Sustainability and Resilience in Urban Areas
Full text linkIn the last decades, a tendency towards urban tissue densification has been observed to counteract the urban sprawl. Densification may be achieved through more compact built areas, preferring the vertical to the horizontal development of buildings but avoiding bulky high-rise building blocks. This strategy significantly affects several aspects of the microclimate and produces direct and indirect effects on human health and well-being. In this regard, air pollution and heat stress constitute two increasing threats to human health and well-being that need to be faced immediately. The involved phenomena are various, intertwined, and may lead to conflicting results. Hence, regenerating existing, well-structured, and stratified urban areas by densification is not an easy challenge. Urban ventilation may favor the mitigation of detrimental effects of air pollution and heat stress on human life. Therefore, a multidisciplinary methodology is presented for embedding urban ventilation performance evaluation into urban management and planning processes. The scope is to propose a framework for urban renewal plans that is citizens-centered and aims at improving their health and well-being in existing urban areas. The methodology builds upon the performance-based approach and is supported by the conceptual framework and the literature reviews provided through the paper
Rigenerazione urbana dell’ex fabbrica di saponi Mira Lanza a Roma: un nuovo scenario di parco resiliente
No full textIl carattere naturalistico dell’area, esaltato dalla vicinanza con il corridoio fluviale romano, si fonde con quello industriale, costituito dalla presenza dell’ex stabilimento della Mira Lanza. Qui l’avanzato degrado ha trasformato i manufatti in veri e propri ruderi di archeologia industriale ed il sito, altamente inquinato, giace in prossimità di una risorsa idrica di grande rilievo, quale il fiume Tevere. Si propone, così, un intervento di fitorimedio in situ a lungo termine; una tecnologia che prevede l’impiego di piante per la bonifica del suolo. Contestualmente, si progetta la realizzazione di un parco urbano, con percorsi attrezzati sopraelevati, che, partendo dalla quota posta ai margini della Mira Lanza, viaggiano, sospesi da terra, tra ruderi industriali e verde. La ricerca proposta, pertanto ha per oggetto la realizzazione di un Parco Resiliente, che sappia adattarsi al contesto specifico e trasformi per la Città tutta le problematiche in opportunità
Impact of morphological parameters on urban ventilation in compact cities. The case of the Tuscolano-Don Bosco district in Rome
Full text linkAir pollution and heat stress are major concerns associated with the liveability, resilience and sustainability of cities. They directly affect health and comfort and are associated with augmented morbidity and mortality and an increase in the energy demand for building ventilation, air cleaning and cooling. Nevertheless, the detrimental effects of poor air quality may partly be mitigated by increased urban ventilation. This strategy is closely related to the level of urbanization and the urban morphology. Therefore, detailed investigations on the impact of different morphologies on urban ventilation are of paramount importance. Computational Fluid Dynamics simulations have been widely used during the last decades to investigate the effects of the urban morphology on the urban ventilation. However, most of these studies focused on idealized building arrangements, while detailed investigations about the role of real urban morphologies are scarce. This study investigates the ventilation in a compact area in the city of Rome, Italy. 3D steady-state Reynolds-averaged Navier-Stokes simulations are performed to analyze the impact of Morphological Parameters (MP) on the urban ventilation. The results show a considerable worsening of urban ventilation with increasing building density with a reduction in the mean wind velocity up to 62% experienced at the pedestrian level (zp). Correlations between five MPs, e.g., plan area density, area-weighted mean building height, volume density, façade area density, and non-dimensional mean velocity at pedestrian level and at 10 m height are evaluated, and simple models are obtained using linear regression analysis. Among the selected MPs, the building façade area density shows a remarkable correlation with the non-dimensional mean velocity at zp (R2 = 0.82). Such correlations can be valuable tools for practitioners and urban designers, particularly during the first stage of planning, for highlighting areas potentially vulnerable to poor air conditions without running computationally expensive simulations
Rigenerazione dei fabbricati viaggiatori della stazione ferroviaria e riqualificazione dell’ex stabilimento delle Fornaci Briziarelli di San Gemini // Regeneration of the passenger buildings of the railway station and redevelopment of the former factory Fornaci Briziarelli in San Gemini
No full textIl Piano Nazionale di Ripresa e Resilienza Umbria 2021-2026, approvato nell’aprile 2021 dalla Giunta Regionale, riconosce nel turismo sostenibile «un potere attivante
sull’economia», tanto da riconoscere la «valorizzazione delle aree interne e dei borghi della regione». La presenza di borghi storici sarà la base per innovare la concezione della mobilità in una chiave aggiornata e impostata sulla rigenerazione turistica del tracciato ferroviario della ex Ferrovia Centrale Umbra. In base al PNRR ci si propone di riconvertire e trasformare i fabbricati viaggiatori della stazione di San Gemini, per ospitare le attrezzature di supporto ai turisti e di bike sharing e l’ex stabilimento Fornaci Briziarelli per la produzione di mattoni, che recuperato, diverrà l’elemento principale dell’intera area. Il fabbricato appartamenti, che ospitava gli operai, avrà la funzione di hotel/bed and breakfast; qui potranno soggiornare i turisti in visita alle bellezze del territorio di San Gemini
Reduced-scale numerical investigation of airflow around low-medium density neighbourhoods from the perspectives of drag force and ventilation efficiency
No full textSustainability of compact cities: the SOS_UrbanLab activity
Full text linkUrban development is facing new challenges to allow the evolution of the environment, in accordance to sustainability principles. In this context, decision makers have to answer to three main issues: how to intervene on the existing compact cities? How to combine and develop interventions on different scales? How to move from requalification to regeneration? The SOS_UrbanLab (Engineering Laboratory for Construction and Environmental Sustainability) researches, starting from a multi-scale analysis, propose a set of eco-friendly solutions to support the potential and capability of territories, integrating their benefits to reach a full sustainable approach
Effects of local conditions on the multi-variable and multi-objective energy optimization of residential buildings using genetic algorithms
No full textThe energy requalification of existing buildings entails the fulfillment of different, often conflicting, criteria, such as the reduction of the specific annual energy demand, the containment of the construction costs, the decrease in the annual energy operating cost and the reduction of climate-change gas emissions. Therefore, optimization methods based on the application of computational algorithms are essential to determine solutions that meet multi-objective criteria and so highly optimized to be on the Pareto frontier. In this work, a procedure for the optimization of existing buildings using genetic algorithms is presented. Building energy simulations conducted in the dynamic regime using EnergyPlus are coupled with an Active Archive Non-dominated Sorting Genetic Algorithm (aNSGA-II type). Using a residential building as a benchmark, this procedure is employed to evaluate the best retrofitting interventions for 19 European cities with different climates. The criteria taken into account in the optimization procedure are: the reduction in the annual specific energy demand, the decrease in the construction and installation costs, the reduction in the annual energy operating costs and the reduction in the greenhouse gas emissions. The results show the most advantageous energy retrofitting interventions fulfilling the criteria for the different geographical sites
Metodología SIG para el cálculo de zonas climáticas locales
No full textLas Zonas Climáticas Locales (ZCL) es una metodología desarrollada por Stewart y Oke (2012) originalmente para describir el área urbana en donde las mediciones meteorológicas se realizan. En los últimos años, ha sido utilizada principalmente para la caracterización de las zonas urbanas y sus particularidades en la morfología urbana. Stewart y Oke (2012) presentan 10 clases urbanas y 7 naturales, cada una de ellas se la caracteriza con parámetros morfológicos y de cobertura, en su propuesta presenta la posibilidad de combinar clases. En relación a las 10 clases urbanas, las tres primeras presentan altas densidades de superficie construida con tres alturas diferentes (altas –1–, medias –2– y bajas –3–); las tres siguientes presentan menores densidades manteniendo las tres clases en altura (altas –4–, medias –5– y bajas –6–); la ZCL 7 se refiere a asentamiento informales con materiales livianos; la ZCL 8 presenta grandes complejos de galpones asociados a actividades comerciales e industriales; la ZCL 9 son áreas de muy baja densidad de construcción con baja altura dominadas por áreas naturales; finalmente la ZCL 10 está asociada a actividades industriales. En cuanto a las ZCL naturales: A para bosques densos; B para bosques dispersos; C para arbustos; D para plantas bajas o producción agrícola; E para áreas con suelo desnudo o rocas; F para áreas con arena; y G para zonas con agua. La escala local es central para la clasificación ya que la superficie ocupada por cada zona no puede tener menos de 400 metros cuadrados (Stewart & Oke 2012).Fil: Picone, Natasha. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto de Geografía, Historia y Ciencias Sociales. Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto de Geografía, Historia y Ciencias Sociales; Argentina. University of Glasgow; Reino UnidoFil: Esposito, Antonio. Universitá del Salento; ItaliaFil: Palusci, Olga. Universitá del Salento; ItaliaFil: Emmanuel, Rohinton. University of Glasgow; Reino UnidoFil: Buccolieri, Riccardo. Universitá del Salento; ItaliaXVIII Conferencia Iberoamericana de Sistemas de Información GeográficaCáceresEspañaRed Iberoamericana de Sistemas de Información GeográficaUniversidad de Extremadura. Instituto Universitario de Investigación para el Desarrollo Territorial Sostenibl
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