Determination of aerodynamic parameters of urban surfaces: methods and results revisited
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Estimates of aerodynamic parameters, in particular roughness length z 0 and displacement height d, are important for the analysis of the roughness of an urban surface, which affects processes that occur within the urban boundary layer such as pollutant dispersion and urban ventilation. Findings regarding the aerodynamic effects of various configurations of urban arrays were compiled from various studies. Several experimental, numerical and semi-empirical studies to estimate z 0 and d were reviewed and compared with each other. The results can be summarized as follows: (1) the influence of the frontal area index (λ f ) on z 0 is significant and their relationship has been confirmed by both experimental and numerical data; (2) compared to one-parameter and two-parameter fitting methods, the three-parameter fitting method is the least accurate; (3) the physical meaning of d remains vague because its definition as the height where surface drag acts may not be accurate for sharp-edged roughness blocks and (4) the peak values of z 0 for uniform and heterogeneous block heights indicate presence of skimming or wake-interference flow effects, which may influence surface roughness. Finally, the semi-empirical models were found to be limited to cases derived from available experimental data, which normally involve uniform arrays of cubes.
KeywordsWind Profile Wind Tunnel Experiment Building Height Urban Surface Surface Shear Stress
This research was financially supported by the Malaysian Ministry of Higher Education (MOHE) under the Fundamental Research Grant Scheme (4 F350) project of Universiti Teknologi Malaysia.
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