Local-scale forcing effects on wind flows in an urban environment: Impact of geometrical simplifications

Ricci, Alessio; Kalkman, I Ivo; Blocken, Bje Bert; Burlando, Massimiliano; Freda, Andrea; Repetto, Maria Pia

doi:10.1016/j.jweia.2017.08.001

Cited by 59 publications

(32 citation statements)

References 41 publications

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“…Many studies have been carried out to investigate the influence of buildings on the airflow and concentration fields (e.g. Zhang et al 2015, Ricci et al 2017. The wind field within the street canyons can look very different from the average wind field with along-street flow and large-scale turbulent eddies.…”

Section: Dispersion Coefficientsmentioning

confidence: 99%

UDINEE: Evaluation of Multiple Models with Data from the JU2003 Puff Releases in Oklahoma City. Part II: Simulation of Puff Parameters

Hernández-Ceballos

Hanna²,

Bianconi³

et al. 2019

Boundary-Layer Meteorol

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The capabilities of nine atmospheric dispersion models in predicting near-field dispersion from puff releases in an urban environment are addressed under the Urban Dispersion INternational Evaluation Exercise (UDINEE) project. The model results are evaluated using tracer observations from the Joint Urban 2003 (JU2003) experiment where neutrallybuoyant puffs were released in the downtown area of Oklahoma City, USA. Sulphur hexafluoride concentration time series measured at ten sampling locations during four daytime and four night-time puff releases are used to evaluate how the models simulate the puff passage at the measurement locations. The neutrally-buoyant puff releases in the JU2003 experiment are the closest scenario to radiological dispersal device (RDD) releases in urban areas, and therefore, UDINEE is a first step towards improving the emergency response to an RDD explosion in the urban environment. We investigate for each puff and sampler the model capability of simulating the peak concentration; the peak and puff arrival times; and time duration, defined as the period over which concentrations exceed 10% of the peak concentration. This analysis points out differences on the performance of models: the fraction within a factor-of-two values ranges from 0.10 to 0.6 for peak concentration, from 0 to 1 for the peak and arrival times, and from 0 to 0.8 for the time duration. The results reveal that the characteristics of the release site largely influence the model simulation as it affects initial puff size and the initial downwind spread of the puff.

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Section: Dispersion Coefficientsmentioning

confidence: 99%

UDINEE: Evaluation of Multiple Models with Data from the JU2003 Puff Releases in Oklahoma City. Part II: Simulation of Puff Parameters

Hernández-Ceballos

Hanna²,

Bianconi³

et al. 2019

Boundary-Layer Meteorol

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“…As the fine features and complexity of the geometry adversely affect the mesh design, a geometry simplification is commonly used as a preprocessing step to improve the mesh quality of the model [10]. Among the numerical analysis processes, the simplification of a complex geometry requires a great deal of manual work and is time-consuming [11].…”

Section: Introductionmentioning

confidence: 99%

Building Geometry Simplification for Improving Mesh Quality of Numerical Analysis Model

et al. 2020

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Numerical analysis, especially the finite volume method (FVM), is one of the primary approaches employed when evaluating a building environment. A complicated geometry can degrade the mesh quality, leading to numerical diffusions and errors. Thus, this study develops and evaluates an automatic building geometry simplification method based on integrating similar surfaces for the geometry of an indoor space. A regression model showed that the complexity of the simplified geometry and its similarity to the original geometry decreased linearly with the threshold of the method. The mesh quality was significantly improved by the simplification. In particular, the maximum skewness decreased exponentially with the threshold of the method. It is expected that the simplification method and regression model presented in this study can be used to quantitatively control the mesh quality.

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“…Several experimental and numerical studies dealt with urban flows over both simplified and complex building geometries, focusing on different spatial scales: street scale (of order 10-100 m), neighbourhood scale (100-1000 m) or city scale (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). A recent work of Ricci et al (2017) highlights the differences occurring in mean and turbulent flow, by means of urban area models with increasing levels of geometrical details. They pointed out how the significant deviations can be caused by geometrical simplifications, although underlining the huge computational power requested for numerical simulations with high level of detail.…”

Section: Introductionmentioning

confidence: 99%

Air exchange in urban canyons with variable building width: a numerical LES approach

Garau

Badas

Ferrari

et al. 2019

IJEP

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The aim of this work is to gain further insight into the role played by the building aspect ratio (ARB, i.e. the ratio of the building width, WB, to the building height, H) and its influence on street canyon flow. We carried out a series of Large Eddy Simulations with arrays of obstacles with different widths, ranging from 0.5 to 2.0, and two canyon aspect ratios (ARC, i.e. the ratio of the canyon width, W, to H) ARC = 0.5 and ARC = 1.0. Experimental data was obtained in a water channel for the corresponding configuration and used to validate numerical simulations. Results were found strongly dependent on the building aspect ratios, with two distinct behaviors identified with respect to the canyon aspect ratio. The residence time decreases with decreasing ARB, irrespective of the canyon aspect ratio, suggesting that ARB and ARC can be optimized to guarantee an optimal street canyon ventilation in urban planning.

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Local-scale forcing effects on wind flows in an urban environment: Impact of geometrical simplifications

Cited by 59 publications

References 41 publications

UDINEE: Evaluation of Multiple Models with Data from the JU2003 Puff Releases in Oklahoma City. Part II: Simulation of Puff Parameters

UDINEE: Evaluation of Multiple Models with Data from the JU2003 Puff Releases in Oklahoma City. Part II: Simulation of Puff Parameters

Building Geometry Simplification for Improving Mesh Quality of Numerical Analysis Model

Air exchange in urban canyons with variable building width: a numerical LES approach

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