4,748 research outputs found
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 Xβhotwire 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
Roughness-sublayer correction for the profiles of mean velocity and turbulence over urban areas
published_or_final_versio
Oral health status and behaviours of preschool children in Hong Kong.
published_or_final_versio
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
Potential use of Niti implant for intra-articular fracture of phalax
Session - New Developments in Orthopaedic Implant Materialspublished_or_final_versio
Isolated penile urethral injury: a rare case following male coital trauma
published_or_final_versio
- β¦