A Laboratory Model of Urban Street-Canyon Flows

Baik, Jong Jin; Park, Rae Seol; Chun, Hye‐Yeong; Kim, Jae Jin

doi:10.1175/1520-0450(2000)039<1592:almous>2.0.co;2

Cited by 125 publications

(59 citation statements)

References 17 publications

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“…e upper recirculation is still shifted downstream (x 0.26H, z 0.71H), according to AR 1, while the lower, atter vortex is centered in the cavity (x 0.26H, z 0.22H). ese results agree reasonably well with the water-channel experiments performed by Baik et al [68] for AR 2, which showed (x 0.32H, z 0.75H) and (x 0.29H, z 0.17H) as the locations of the centers of the upper and lower recirculation regions, respectively.…”

Section: E Ect Of Aspect Ratio Variationssupporting

confidence: 91%

“…Furthermore, the external wind ows above the canopy almost parallel to the roofs, resulting in a poor canyon ventilation process, are strongly hampered by the structure of the vortices. is corroborates the idea that, for the skimming ow, the uid has di culty in penetrating the interelement spaces, and therefore it skims, remaining nearly parallel to the roofs [68,70]. For this reason, it is fundamental to consider a correct urban planning to minimize unwanted e ects of pollutant accumulation.…”

Section: E Ect Of Aspect Ratio Variationssupporting

confidence: 75%

“…is paper concludes with a summary of the main results. e water channel allows the reproduction of the atmospheric boundary layer with several advantages [38][39][40][41]. One of them is that image analysis techniques, such as particle tracking velocimetry, can be easily employed.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

Nardecchia

Bernardino

Pagliaro

et al. 2018

Advances in Meteorology

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Computational fluid dynamics (CFD) is currently used in the environmental field to simulate flow and dispersion of pollutants around buildings. However, the closure assumptions of the turbulence usually employed in CFD codes are not always physically based and adequate for all the flow regimes relating to practical applications. e starting point of this work is the performance assessment of the V2F (i.e., v 2 − f ) model implemented in Ansys Fluent for simulating the flow field in an idealized array of twodimensional canyons. e V2F model has been used in the past to predict low-speed and wall-bounded flows, but it has never been used to simulate airflows in urban street canyons. e numerical results are validated against experimental data collected in the water channel and compared with other turbulence models incorporated in Ansys Fluent (i.e., variations of both k-ε and k-ω models and the Reynolds stress model). e results show that the V2F model provides the best prediction of the flow field for two flow regimes commonly found in urban canopies. e V2F model is also employed to quantify the air-exchange rate (ACH) for a series of two-dimensional building arrangements, such as step-up and step-down configurations, having different aspect ratios and relative heights of the buildings. e results show a clear dependence of the ACH on the latter two parameters and highlight the role played by the turbulence in the exchange of air mass, particularly important for the step-down configurations, when the ventilation associated with the mean flow is generally poor.

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Section: E Ect Of Aspect Ratio Variationssupporting

confidence: 91%

Section: E Ect Of Aspect Ratio Variationssupporting

confidence: 75%

See 1 more Smart Citation

CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

Nardecchia

Bernardino

Pagliaro

et al. 2018

Advances in Meteorology

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“…The Reynolds number, Re, is defined as Re = U re f H/ν, where U re f is a reference velocity, H the canyon height and ν the kinematic viscosity. In all cases, the Reynolds numbers were above 10,000 to achieve fully turbulent regime [37][38][39]. The water depth was 3.4H for case (i) and 3.8H for cases (ii)-(iv).…”

Section: Methodsmentioning

confidence: 99%

Pedestrian-Level Urban Wind Flow Enhancement with Wind Catchers

2017

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Dense urban areas restrict air movement, causing airflow in urban street canyons to be much lower than the flow above buildings. Boosting near-ground wind speed can enhance thermal comfort in warm climates by increasing skin convective heat transfer. We explored the potential of a wind catcher to direct atmospheric wind into urban street canyons. We arranged scaled-down models of buildings with a wind catcher prototype in a water channel to simulate flow across two-dimensional urban street canyons. Velocity profiles were measured with Acoustic Doppler Velocimeters. Experiments showed that a wind catcher enhances pedestrian-level wind speed in the target canyon by 2.5 times. The flow enhancement is local to the target canyon with little effect in other canyons. With reversed flow direction, a "reversed wind catcher" has no effect in the target canyon but reduces the flow in the immediate downstream canyon. The reversed wind catcher exhibits a similar blockage effect of a tall building amid an array of lower buildings. Next, we validated Computational Fluid Dynamics (CFD) simulations of all cases with experiments and extended the study to reveal impacts on three-dimensional ensembles of buildings. A wind catcher with closed sidewalls enhances maximum pedestrian-level wind speed in three-dimensional canyons by four times. Our results encourage better designs of wind catchers to increase wind speed in targeted areas.

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“…Physical modeling involves simulation of airfl ow and pollutant dispersion using wind-tunnel (Rafailidis & Schatzmann, 1995;Meroney, Rafailidis & Pavageau 1996;Meroney, Leitl & Rafailidis, 1999, Pavageau & Schatzmann, 1999Kastner-Klein & Plate, 1999;Baker & Hargreaves, 2001;Kovar et al, 2002, Gromke & Ruck, 2007 water channel (Baik & Kim 2000;Caton, Britter & Dalziel, 2003;Kim & Baik, 2005;Li, Leung, Liu & Lam, 2008), where fl ow can be controlled, and complex urban morphology can be simulated in fi ne details, i.e. including facades, arbitrary roof shape, trees and other street furniture.…”

Section: Introductionmentioning

confidence: 99%

A numerical analysis of pollutant dispersion in street canyon: influence of the turbulent Schmidt number

Abed

Bouarbi

Bouzit

et al. 2017

Przegląd Naukowy Inżynieria I Kształtowanie Środowiska

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Realizing the growing importance and availability of motor vehicles, we observe that the main source of pollution in the street canyons comes from the dispersion of automobile engine exhaust gas. It represents a substantial effect on the micro-climate conditions in urban areas. Seven idealized-2D building configurations are investigated by numerical simulations. The turbulent Schmidt number is introduced in the pollutant transport equation in order the take into account the proportion between the rate of momentum turbulent transport and the mass turbulent transport by diffusion. In the present paper, we attempt to approach the experimental test results by adjusting the values of turbulent Schmidt number to its corresponding application. It was with interest that we established this link for achieving our objectives, since the numerical results agree well with the experimental ones. The CFD code ANSYS CFX, the k, e and the RNGk-e models of turbulence have been adopted for the resolutions. From the simulation results, the turbulent Schmidt number is a range of 0.1 to 1.3 that has some effect on the prediction of pollutant dispersion in the street canyons. In the case of a flat roof canyon configuration (case: runa000), appropriate turbulent Schmidt number of 0.6 is estimated using the k-epsilon model and of 0.5 using the RNG k-e model.

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A Laboratory Model of Urban Street-Canyon Flows

Cited by 125 publications

References 17 publications

CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

Pedestrian-Level Urban Wind Flow Enhancement with Wind Catchers

A numerical analysis of pollutant dispersion in street canyon: influence of the turbulent Schmidt number

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