Untitled

Ketzel, Matthias; Berkowicz, Ruwim; Lohmeyer, Achim

doi:10.1023/a:1006460724703

Cited by 27 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We intend to show here that transport and dispersion in urban canyons can be elucidated via multivariable frequency analysis of synchronized time series of wind and PM concentration data. Specifically, we show that transport is strongest when wind azimuth approaches the street azimuth, confirming findings in other wind tunnel studies in the literature, for example, Ketzel et al 13 In addition, using Eigen-frequency analysis we show that PM concentrations comprise periodic components that reflect vehicular emissions from traffic, demonstrating that downwind concentrations can be linked to traffic patterns. The approach presented in this paper is based on analysis of several sets of timeseries data, including simultaneous wind speed, wind direction, and contaminant concentrations measured at several locations within a 5 s synchronization.…”

Section: Introductionsupporting

confidence: 89%

Establishing a link between vehicular PM sources and PM measurements in urban street canyons

et al. 2009

View full text Add to dashboard Cite

The Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study, conducted in Brooklyn, NY, USA, in 2005, was designed with multiple goals in mind, two of which were contaminant source characterization and street canyon transport and dispersion monitoring. In the portion of the study described here, synchronized wind velocity and azimuth as well as particulate matter (PM) concentrations at multiple locations along 33rd Street were used to determine the feasibility of using traffic emissions in a complex urban topography as a sole tracer for studying urban contaminant transport. We demonstrate in this paper that it is possible to link downwind concentrations of contaminants in an urban street canyon to the vehicular traffic cycle using Eigen-frequency analysis. In addition, multivariable circular histograms are used to establish directional frequency maxima for wind velocity and contaminant concentration.

show abstract

Section: Introductionsupporting

confidence: 89%

Establishing a link between vehicular PM sources and PM measurements in urban street canyons

et al. 2009

View full text Add to dashboard Cite

show abstract

“…In the present article, the numerical model MISKAM (EICHHORN, 1989) has been used to simulate flow and pollutant concentrations in street canyons with tree planting. MISKAM has been employed and validated for several pollutant concentration studies in urban environments, such as KETZEL et al (2000), SAHM et al (2002), andGORICSÁN et al (2009). A k-ε turbulence model has been employed to close the RANS equations.…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of flow and pollutant dispersion in street canyons with tree planting

Bálczó¹,

Ruck²

2009

metz

107

View full text Add to dashboard Cite

Numerical simulations of the impact of tree planting on airflow and traffic pollutant dispersion in urban street canyons have been performed using the commercial CFD (Computational Fluid Dynamics) code MISKAM. A k-ε turbulence model including additional terms for the treatment of vegetation, has been employed to close the Reynolds-averaged-Navier-Stokes (RANS) equations. The numerical results were compared to wind tunnel data. In the case of the investigated wind direction perpendicular to the street axis, the presence of trees lead to increased pollutant concentrations inside the canyon. Concentrations increased strong on the upstream side of the canyon, while on the downstream side a small concentration decrease could be observed. Lower flow velocities and higher pollutant concentrations were found in the numerical simulations when directly compared to the experimental results. However, the impact of tree planting on airflow and concentration fields when compared to the treeless street canyon as a reference configuration were simulated quite well, meaning that relative changes were similar in the wind tunnel investigations and numerical computations. This feature qualifies MISKAM for use as a tool for assessing the impacts of vegetation on local air quality. Zusammenfassung Numerische Simulationen über die Auswirkungen von Baumpflanzungen auf die Strömungsverhältnisse und die Ausbreitung von Verkehrsemissionen in städtischen Straßenschluchten wurden mit dem kommerziellen CFD (Computational Fluid Dynamics) Code MISKAM durchgeführt. Ein k-ε Turbulenzmodell mit speziellen Zusatztermen zur Vegetationsberücksichtigung kam zum Einsatz um die Reynoldsaveraged-Navier-Stokes (RANS) Gleichungen zu schließen. Die numerischen Berechnungsergebnisse wurden mit Windkanalergebnissen verglichen. Im Fall der untersuchten Windrichtung senkrecht zur Straßenlängsachse führten die Baumpflanzungen zu im Mittel höheren Konzentrationen innerhalb der Straßenschlucht. Deutliche Konzentrationszunahmen waren an der leeseitigen Straβenschluchtwand zu verzeichnen, während an der luvseitigen Wand nur geringe Konzentrationsabnahmen zu beobachten waren. Die numerischen Simulationen ergaben geringere Windgeschwindigkeiten und höhere Schadstoffkonzentrationen gegenüber den experimentellen Ergebnissen. Jedoch wurden die Auswirkungen von Baumpflanzungen auf die Strömungs-und Konzentrationsfelder insofern zufriedenstellend simuliert, als dass die relativen Änderungen im Vergleich zur baumfreien Straßenschlucht als Referenzfall eine gute Übereinstimmung mit den Windkanalmessungen aufwiesen. Somit erweist sich MISKAM geeignet den Einfluss von Vegetation auf die Luftqualität im Straβenschluchtbereich einzuschätzen.

show abstract

“…Depaul and Sheih 1986;Qin and Kot 1993;Rotach 1995;Kousa et al 2001;Vachon et al 2001;Ketzel et al 2002;Kastner-Klein et al 2003). Although such experiments provide the ultimate real data, there are a number of weaknesses: low spatial resolutions, uncontrollable meteorological conditions, and complex building configurations.…”

Section: Introductionmentioning

confidence: 99%

Large‐eddy simulation of turbulent flow in a street canyon

Cui

Cai

Baker

2004

Quart J Royal Meteoro Soc

112

View full text Add to dashboard Cite

SUMMARYThe turbulent flow inside an idealized urban street canyon with an aspect ratio of one is studied by means of large-eddy simulation. The Regional Atmospheric Modelling System is configured to simulate the turbulent flow in a neutrally stratified atmosphere with the initial wind perpendicular to the street canyon axis. The mean velocity components, resolved-scale turbulent kinetic energy (RS-TKE), the skewness and kurtosis of the resolved-scale velocity components (u along the canyon and w vertically) are compared with wind-tunnel measurements. The comparison indicates that a reasonable agreement is achieved. The simulation slightly underestimates the intensity of the primary eddy. It is found that distribution of the RS-TKE is very asymmetric: high in the vicinity of the downstream wall, and uniformly low in the vicinity of the upstream wall. The analyses of skewness and kurtosis indicate that there is a layer just below the rooftop in the canyon where ejection events dominate. Quadrant analysis of resolved-scale velocity fluctuations, u and w , under the rooftop at the centre of the canyon reveals that the exchange of momentum across the canyon top is contributed unevenly by different events. Weak ejection events dominate the frequency of occurrences, but fewer strong sweep events contribute the majority of the total momentum transfer. The features of momentum transfer are further investigated by analysing the spatial-temporal variations of u , w , and u w at the roof level. It is found that the variation of these variables is highly intermittent and is associated with multi-scale turbulent events. The period of eddies containing high RS-TKE is attributed to the Kelvin-Helmhotz instabilities. These results improve our understanding of the turbulent structure in street canyon flow.

show abstract

Untitled

Cited by 27 publications

References 0 publications

Establishing a link between vehicular PM sources and PM measurements in urban street canyons

Establishing a link between vehicular PM sources and PM measurements in urban street canyons

Numerical modeling of flow and pollutant dispersion in street canyons with tree planting

Large‐eddy simulation of turbulent flow in a street canyon

Contact Info

Product

Resources

About