A wind tunnel study of organised and turbulent air motions in urban street canyons

Klein, Petra M.; Fedorovich, Evgeni; Rotach, Mathias W.

doi:10.1016/s0167-6105(01)00074-5

Cited by 186 publications

(107 citation statements)

References 11 publications

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“…In a similar study, Rafailidis (1997) still observed pronounced peaks in Reynolds stress and turbulence intensity profiles above an array of idealized street canyons for particular roof shapes. Kastner-Klein et al (2001) analyzed mean flow and turbulence data measured in wind-tunnel models of idealized street canyons in comparison with data from corresponding field studies, and found qualitative similarity between wind-tunnel flow characteristics and their atmospheric counterparts. Cheng and Castro (2002) presented detailed mean flow and turbulence data inside and above idealized urban surfaces, which consisted of regularly spaced (packing density 25%) cubes and rectangular blocks.…”

Section: Introductionmentioning

confidence: 98%

Mean Flow and Turbulence Characteristics in an Urban Roughness Sublayer

Klein

Rotach

2004

Boundary-Layer Meteorology

212

122

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Abstract. In this study, a detailed model of an urban landscape has been re-constructed in the wind tunnel and the flow structure inside and above the urban canopy has been investigated. Vertical profiles of all three velocity components have been measured with a Laser-Doppler velocimeter, and an extensive analysis of the measured mean flow and turbulence profiles carried out. With respect to the flow structure inside the canopy, two types of velocity profiles can be distinguished. Within street canyons, the mean wind velocities are almost zero or negative below roof level, while close to intersections or open squares, significantly higher mean velocities are observed. In the latter case, the turbulent velocities inside the canopy also tend to be higher than at street-canyon locations. For both types, turbulence kinetic energy and shear stress profiles show pronounced maxima in the flow region immediately above roof level.Based on the experimental data, a shear-stress parameterization is proposed, in which the velocity scale, u s , and length scale, z s , are based on the level and magnitude of the shear stress peak value. In order to account for a flow region inside the canopy with negligible momentum transport, a shear stress displacement height, d s , is introduced. The proposed scaling and parameterization perform well for the measured profiles and shear-stress data published in the literature.The length scales derived from the shear-stress parameterization also allow determination of appropriate scales for the mean wind profile. The roughness length, z 0 , and displacement height, d 0 , can both be described as fractions of the distance, z s − d s , between the level of the shear-stress peak and the shear-stress displacement height. This result can be interpreted in such a way that the flow only feels the zone of depth z s − d s as the roughness layer. With respect to the lower part of the canopy (z < d s ) the flow behaves as a skimming flow. Correlations between the length scales z s and d s and morphometric parameters are discussed.The mean wind profiles above the urban structure follow a logarithmic wind law. A combination of morphometric estimation methods for d 0 and z 0 with wind velocity measurements at a reference height, which allow calculation of the shear-stress velocity, u * , appears to be the most reliable and easiest procedure to determine mean wind profile parameters. Inside the roughness sublayer, a local scaling approach results in good agreement between measured and predicted mean wind profiles.

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Section: Introductionmentioning

confidence: 98%

Mean Flow and Turbulence Characteristics in an Urban Roughness Sublayer

Klein

Rotach

2004

Boundary-Layer Meteorology

212

122

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“…To better understand its complex nature, wind-tunnel or waterchannel experimental studies (e.g., Kastner-Klein et al 2001;Princevac et al 2010), numerical modeling studies (Letzel et al 2012;Park et al 2013), and field experimental studies (e.g., Brown et al 2004;Zajic et al 2011) have been performed extensively.…”

Section: Introductionmentioning

confidence: 99%

Measurements of Turbulent Flow and Ozone at Rooftop and Sidewalk Sites in a High-Rise Building Area

Park¹,

Kwak²,

Han³

et al. 2015

SOLA

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Turbulent flow and ozone concentration at two (rooftop and sidewalk) sites in a high-rise building area of Seoul, Republic of Korea, were measured for the period of 24−27 June 2013 to examine their characteristics according to site location. During the observation period, the diurnal variations of air temperature, wind speed, and turbulent kinetic energy were distinct at both sites. The time series of ozone concentration exhibits a diurnal variation with daytime double peaks and one nighttime peak at both sites. The horizontal wind direction at the rooftop site has variations related to local winds, while the horizontal wind direction at the sidewalk site is mostly southerly (following a nearby street). The multiresolution spectra of horizontal and vertical velocities at the rooftop site confirm diurnal and turbulence-related variations. A quadrant analysis indicates that turbulence at the rooftop site is characterized by frequent ejections and less frequent but stronger sweeps, while turbulence at the sidewalk site is weaker and less characterizable than turbulence at the rooftop site.

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“…These discrepancies were thought to be caused by the difficulty in specifying reference parameters, such as the friction velocity, displacement height or roughness length. This problem has also been partly described by Kastner-Klein et al (2001). The geometry of the buildings and, in general, of the urban area also has a major influence on the production of turbulence inside and outside a canyon.…”

Section: Introductionmentioning

confidence: 99%

“…Despite these studies, details of the exchange mechanisms, and the velocities and fluxes between a canyon and the flow above, are not well understood and stand in need of further research. Kastner-Klein et al (2001) underlined a common difficulty encountered in many studies. Observations from field measurements can rarely be compared with data from either wind tunnel or computational approaches.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Mapping of Air Flow at an Urban Canyon Intersection

Carpentieri

Robins

Baldi

2009

Boundary-Layer Meteorol

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In this experimental work both qualitative (flow visualisation) and quantitative (laser Doppler anemometry) methods were applied in a wind tunnel in order to describe the complex 3-dimensional flow field in a real environment (a street canyon intersection). The main aim was an examination of the mean flow, turbulence and flow pathlines characterising a complex 3-dimensional urban location. The experiments highlighted the complexity of the observed flows, particularly in the upwind region of the intersection. In this complex and realistic situation some details of the upwind flow, such as the presence of two tall towers, play an important role in defining the flow field within the intersection, particularly at roof level. This effect is likely to have a strong influence on the mass exchange mechanism between the canopy flow and the air aloft, and therefore the distribution of pollutants. This strong interaction between the flows inside and outside the urban canopy is currently neglected in most state-of-the-art local scale dispersion models.

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A wind tunnel study of organised and turbulent air motions in urban street canyons

Cited by 186 publications

References 11 publications

Mean Flow and Turbulence Characteristics in an Urban Roughness Sublayer

Mean Flow and Turbulence Characteristics in an Urban Roughness Sublayer

Measurements of Turbulent Flow and Ozone at Rooftop and Sidewalk Sites in a High-Rise Building Area

Three-Dimensional Mapping of Air Flow at an Urban Canyon Intersection

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