Abstract
Wind characteristics within the atmospheric boundary layer (ABL) have always been subject to wide attentions in the field of wind engineering. A well-established understanding of boundary layer wind characteristics can not only facilitate the wind-resistant design of high-rise and long-span structures, it also provides valuable information for many other fields, such as wind energy development, urban wind environment, air pollution dispersion, as well as aviation meteorology.The research works contained in this thesis cover two major parts: the first part presents the investigation of wind characteristics within the ABL, while the second part demonstrates the practical applications in various aspects in relation to the boundary layer wind characteristics.
In the first part, a series of boundary layer wind characteristics, including gust factor and vertical profiles of horizontal mean wind speed, are estimated based on wind measurements obtained from a variety of observation equipment at numerous weather stations in Hong Kong. Comparative analyses are carried out with respect to different wind events, namely tropical cyclone, monsoon and thunderstorm. For the assessment of gust factor, a 6-year database is used to determine the characteristics of gust factor at various weather stations. The statistical properties, correlations of gust factor with mean wind speed and averaging time, as well as the effect of topography, are evaluated respectively in regard to different wind events and terrain conditions. As for the assessment of vertical wind profiles, wind measurements obtained by a Doppler radar profiler are adopted and categorized according to different wind events. The differences in terms of the shapes of profiles, gradient height, power-law exponent, wind shear coefficient and some other parameters are presented and discussed. Last but not least, a light detection and ranging (LiDAR) system, equipped at an offshore platform near Clear Water Bay, Hong Kong, is employed to assess the offshore wind characteristics. The fidelity of wind LiDAR measurement is examined. Statistical analysis of mean wind speed, wind shear coefficient, turbulence intensity and gust factor are conducted. In addition, the height-dependence of mean wind speed, turbulence intensity and Weibull parameters, are investigated as well. The outcomes are expected to benefit the future development of offshore wind farms in Hong Kong and the surrounding areas.
In the second part, wind characteristics within the ABL are well utilized to aid the practical applications in several engineering fields. Based on the wind measurements at various weather stations in Hong Kong, a comprehensive assessment of wind characteristics and wind energy potential at different terrain conditions across the territory of Hong Kong is performed by means of statistical analysis using Weibull distribution function. The values of Weibull parameters corresponding to a variety of temporal scales are calculated, which are applied to determine several characteristic parameters associated with wind energy development and wind turbine optimization. In particular, investigations of wind characteristics and wind energy potential at different offshore areas are delivered, which attempts to accelerate the offshore wind energy development in Hong Kong. Although previous wind energy projects are predominantly carried out in offshore areas or rural sites owing to the considerations of economic feasibility and operation safety, it is worthwhile mentioning that wind energy development in urban environment also reveals perspectives with respect to the mitigation of carbon footprint. Pearl River Tower, a 79-storey building in Guangzhou, China, was designed to be the most energy efficient tall building in the world. In addition to a series of energy-efficient strategies, the most iconic innovation in the design of Pearl River Tower is the deployment of four wind turbines installed in four openings in the tall building for power generation. Wind tunnel testing is implemented to estimate the wind speed amplification effects inside the four tunnels. The results are subsequently used, in conjunction with long-term meteorological data, to predict the performance of the four wind turbines embodied in these tunnels. Apart from the applications associated with urban wind energy, the boundary layer wind characteristics are also applied to facilitate the environment impact assessment of relocating a sewage treatment work into a nearby cavern. Assessments on both the odor impact and pedestrian-level wind environment are carried out based on a physical model testing at a boundary layer wind tunnel.
| Date of Award | 23 Jun 2016 |
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| Original language | English |
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| Supervisor | Qiusheng LI (Supervisor) |