Shaping buildings to promote street ventilation: A large-eddy simulation study

Llaguno-Munitxa, Maider; Bou‐Zeid, Elie

doi:10.1016/j.uclim.2018.08.006

Cited by 46 publications

(23 citation statements)

References 51 publications

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“…2015; Yang et al. 2016; Llaguno-Munitxa, Bou-Zeid & Hultmark 2017; Llaguno-Munitxa & Bou-Zeid 2018) of regular (Kanda et al. 2004; Placidi & Ganapathisubramani 2015) or irregular (Chester et al.…”

Section: Resultsunclassified

“…The parameter space that characterizes the surface geometry is large. A non-exhaustive list of studies includes previous works that have investigated height variations (Yang et al 2016), geometric shapes (Leonardi et al 2015;Yang et al 2016;Llaguno-Munitxa et al 2017;Llaguno-Munitxa & Bou-Zeid 2018) of regular (Kanda et al 2004;Placidi & Ganapathisubramani 2015) or irregular (Chester et al 2007;Yuan & Jouybari 2018) surface roughness elements, as well as statistical moments of roughness elements (Zhu et al 2017). We do not aim to comprehensively examine the parameter space in this paper, but we are more interested in the general transition of the flow as the roughness, conserving the same area density λ p , changes from slender elements with low λ f to wide ones with high λ f .…”

Section: Effects Of Surface Geometrymentioning

confidence: 99%

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Contrasts between momentum and scalar transport over very rough surfaces

Bou‐Zeid

2019

J. Fluid Mech.

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Large-eddy simulations are conducted to contrast momentum and passive scalar transport over large, three-dimensional roughness elements in a turbulent channel flow. Special attention is given to the dispersive fluxes, which are shown to be a significant fraction of the total fluxes within the roughness sublayers. Based on point-wise quadrant analysis, the turbulent components of the transport of momentum and scalars are found to be similar in general, albeit with increasing dissimilarity for roughnesses with low frontal blockage. However, strong dissimilarity is noted between the dispersive momentum and scalar fluxes, especially below the top of the roughness elements. In general, turbulence is found to transport momentum more efficiently than scalars, while the reverse applies for the dispersive contributions. The effects of varying surface geometries, measured by the frontal density, can be pronounced on both turbulent and dispersive fluxes. Increasing frontal density induces a general transition in the flow from a rough boundary-layer type to a mixed-layer-like type. This transition results in an increase in the efficiency of turbulent momentum transport, but the reverse occurs for scalars due to reduced contributions from large scale motions in the roughness sublayers. This study highlights the need for distinct parameterizations of the dispersive scalar fluxes and the importance of considering the contrasts between momentum and scalar transport for turbulent flows over very rough surfaces.

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Section: Resultsunclassified

Section: Effects Of Surface Geometrymentioning

confidence: 99%

Contrasts between momentum and scalar transport over very rough surfaces

Bou‐Zeid

2019

J. Fluid Mech.

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“…As highlighted by previous studies 7 and confirmed by the results here, the aerodynamic properties of cities also con-tribute to regulating the intensity of UHIs. However, how complex, non-uniform, urban geometries influence the exchange of heat and momentum at the land surface is still a subject of open research, especially at the scales that are relevant for urban design 40 . Our analysis confirms that albedo management is also a viable option to reduce warming at the city scale 2,46 but, given the seasonality of urban warming 9 , albedo modifications can promote winter cooling and increase energy demand, especially in cold regions 41 .…”

Section: Climate-sensitive Urban Planningmentioning

confidence: 99%

“…Hence, while ∆T s is a good proxy for UHI intensity at the global scale with the advantage of providing a theoretical basis for the factorization of the different mechanisms regulating the surface energy balance7 , a climate-sensitive design of cities should also account for site-specific urban and climate characteristics as well as air-surface temperature feedback. Our global analysis inevitably sacrifices such fine-scale processes and detailed numerical simulations remain essential to describe the complexity and heterogeneity of real cities from the building to the regional scale40,41 .High-resolution simulations, however, are computationally expensive, require detailed information about city texture and building material, and municipalities around the world are often called to make planning decisions without any city-specific analysis. Hence, the coarse-grained approach here can provide a first order guideline on expected cooling effects valid across different regions, future climate, and population scenarios to complement micro-scale monitoring and modeling studies.…”

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confidence: 99%

Magnitude of urban heat islands largely explained by climate and population

Manoli

Fatichi

Schläpfer

et al. 2019

Nature

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696

352

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Urban heat islands (UHIs) exacerbate the risk of heat-related mortality associated with global climate change. The intensity of UHIs is known to vary with population size and mean annual precipitation but a unifying argument is missing, and geographically targeted guidelines for heat mitigation remain elusive. Here we analyze urban-rural surface temperature differences (∆T s) worldwide and find a nonlinear increase of ∆T s with precipitation that is controlled by water/energy limitations on evapotranspiration and that modulates the scaling of ∆T s with city size. We introduce a coarse-grained model linking population, background climate, and UHI intensity and we show that urban-rural changes in evapotranspiration and convection efficiency are the main determinants for warming. The direct implication of these nonlinearities is that mitigation strategies aimed at increasing green cover and albedo are more efficient in dry regions, while cooling tropical cities is a challenge that will require innovative solutions.

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“…The purpose of digging the street wind path is to improve the city air quality which further improves livability [19]. Computational fluid dynamics (CFD) can simulate the wind field of the street and find the ventilation characteristics of the street shape, Geographic Information System (GIS) can calculate the shape index related to the ventilation potential, thereby quantifying the entire urban area [20,21].…”

Section: Introductionmentioning

confidence: 99%

The Ventilation Path Assessment of Urban Street in Wuhan

Yin¹,

Zhan²,

Tayyab³

2021

Pol. J. Environ. Stud.

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The urban ventilation path can help to alleviate the heat island effect and air pollution. The building ventilation method is based on building front area density, the building data is divided into grids with numerical attributes, to detect ventilation path. The urban morphology is including building and street, while this building method ignores the ventilation path of the urban street. The streets are most closely connected with people's lives. The direction of the street is the main evaluation index to extract the street ventilation path, which is the supplement of the building method. The spatial analysis technology of Geographic Information System (GIS) was used to calculate the front area density, the street direction, the street length, and the street aspect ratio. These indicators are related to ventilation potential and simulated by Computational Fluid dynamics (CFD). Under different wind directions including the vertical and parallel to the street, it found that the street ventilation potential is different as to the street aspect ratio, if the wind direction is parallel to the street, the street ventilation is better with the decrease of street aspect ratio; if the wind direction is perpendicular to the street, the street ventilation is better with the increase of the street aspect ratio. In the grids of high front area density, there are also some potential ventilation urban streets.

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Shaping buildings to promote street ventilation: A large-eddy simulation study

Cited by 46 publications

References 51 publications

Contrasts between momentum and scalar transport over very rough surfaces

Contrasts between momentum and scalar transport over very rough surfaces

Magnitude of urban heat islands largely explained by climate and population

The Ventilation Path Assessment of Urban Street in Wuhan

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