Wind tunnel study on flows over various two-dimensional idealized urban-like surfaces

Extensive human activities (e.g. increased traffic emissions) emit a wide range of pollutants resulting in poor urban area air quality. Unlike open, flat and homogenous rural terrain, urban surface is complicated by the presence of buildings, obstacles and narrow streets. The irregular urban surfaces thus form a random roughness that further modifies the near-surface flows and pollutant dispersion. In this study, a physical modelling approach is employed to commence a series of wind tunnel experiments to study the urban-area air pollution problems. The flow characteristics over different hypothetical urban roughness surfaces were studied in a wind tunnel in isothermal conditions. Preliminary experiments were conducted based on six types of idealized two-published_or_final_versio

Experimental study on near-ground boundary layer response to the change in different patterns of urban-type surface

The flow behaviour over various two-dimensional (2D) urban-type surfaces was investigated in a laboratory wind tunnel. Square aluminium bars of size 2.5 cm were used to represent flat-roof buildings and the building separation was adjusted to fabricate various types of urban surface of building-height-to-street-width (aspect) ratios of 1, 1/2, 1/8, 1/10 and 1/12. Mean velocities and velocity fluctuations were measured with a 90o X–hotwire anemometry. The current results compare well with our previous large-eddy simulation (LES). Analysis of the turbulence characteristics for different urban surfaces was performed in attempt to examine the near-ground boundary layer response to various street-canyon configurations.postprin

Influence of atmospheric boundary layer depth on the ventilation performance over idealized urban surfaces

The mechanism of flows and scalar transfer over urban areas is complicated by the random city surfaces in which a detailed investigation is required in its parameterization. Despite the collective effort made by the researchers on urban air pollution problems, our knowledge on the interaction between flows and aerodynamic resistance over cities is limited. Apart from the roughness effect induced by the bottom of the urban boundary layer (UBL), the local atmospheric environment conditions and the city-level air quality are closely correlated but their importance is apparently overlooked. Therefore, as a pilot attempt, this study is conceived to examine the effect of UBL depth on the ...published_or_final_versio

Street-Level Ventilation in Hypothetical Urban Areas

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Roughness-sublayer correction for the profiles of mean velocity and turbulence over urban areas

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Parameterisation of flows and pollutant transport over idealised urban roughness

No. J7.2Atmospheric flow over urban areas basically is a type of turbulent flow over roughness. The flows and pollutant transport process, especially at the lower part of the boundary layer (BL), is strongly modified due to the presence of building geometry. The aerodynamic resistance exerted by the surface roughness reduces the mean velocity in the lower BL but enhances the turbulence intensity. Moreover, the near-wall impingement structures over rough surfaces are attributed to the flow dynamics aloft, leading to increasing aerodynamic resistance and BL depth. However, the dependence on surface morphology and BL depth is not yet well understood. There is ...postprin

A rule-based acceleration control scheme for an induction motor

Author name used in this publication: Y. K. WongAuthor name used in this publication: S. L. Ho2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A simulation study on sensorless control of permanent magnet synchronous motor drives

Author name used in this publication: Tze-Fun ChanRefereed conference paper2006-2007 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Speed estimation of an induction motor drive using an optimized extended Kalman filter

Author name used in this publication: K. L. ShiAuthor name used in this publication: Y. K. WongAuthor name used in this publication: S. L. Ho2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe