Abstract
Natural ventilation dominates the heat dissipation and pollutant dispersion in modern cities. Investigations into the flow structure and urban heat island in the Kuala Lumpur City Centre (KLCC) have been conducted by a few researchers. However, these studies were mainly accomplished by means of computational fluid dynamics. The critical problem with computational analysis is the lack of verification. As such, in this research, experimental tools such as the wind tunnel, hotwire anemometry, Pitot tube, and pressure and temperature sensors were utilized. The aim was to assess the ventilation performance of different city models with a height-to-width ratio that was similar to that of the KLCC. Several steps had to be performed before starting the study, among these being the building of the model. A 6×6 array of uniform acrylic blocks (50×50×100 mm) were arranged in line at equal distances. Three arrangements, representing different building densities (35, 25 and 15 %), were examined in the current research. The freestream wind speed was fixed at 5 m/s. The flow was found to be comprised of vortical structures, and attained an energetic turbulence in the downstream of the building areas as compared to the free flow areas. This study suggests keeping the plane area ratio in high-rise building cities within a 15-25% range. The study is beneficial to town planners as the construction of more skyscrapers is being planned.
Highlights
The urban heat island (UHI) phenomenon is the condition when a metropolitan area is significantly hotter than its rural surrounding due to entrapment of heat within the buildings and their surroundings
While the average building dimensions were obtained by exporting every building in Kuala Lumpur City Centre (KLCC) separately to a Stereolithography (STL) file which was later handled by Scilab® to get building length, width and height
The velocity profile and turbulence intensity measurements were performed in an open-circuit blow type, low-speed turbulent boundary layer wind tunnel at the Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia (UKM), this wind tunnel frequently referred to as Pangkor-Low Speed Wind Tunnel (LST)
Summary
The urban heat island (UHI) phenomenon is the condition when a metropolitan area is significantly hotter than its rural surrounding due to entrapment of heat within the buildings and their surroundings. Hang et al (2011) numerically and experimentally investigated the wind flow through arrays of idealized high-rise buildings with aspect ratios from 2 to 5.3 and plane area density 0.25 or 0.4. They delivered recommendations for planning high-rise building cities. Liu et al (2011) conducted CFD analysis for wind flow through 2D street canyons with a wide range of aspect ratios They indicated the importance of turbulence in air change and pollutant removal. Gousseau et al (2011) simulated the pollutant dispersion in downtown Montreal, Canada, using two different modeling approaches (RANS and LES) They validated the results by wind tunnel experiments using a 1/200 scale model of the urban area.
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