Abstract
Wind loads are the dominant loads for large-scale buildings and structures in tropical cyclone-prone regions; however, wind characteristics in tropical cyclones are still far from being understood. In this study, wind characteristics concerned in engineering applications, for example, wind attack angle, friction velocity, drag coefficient, turbulence intensity, integral scale, gust factor, and peak factor, were carefully investigated based on field measurements in typhoon Hagupit and were compared with measurements in typhoon Maemi and three hurricanes in literatures. The results show that drag coefficient increases with mean wind speeds at low levels and then decreases gradually at wind speed greater than 22.45 m/s in typhoon Hagupit over sea surface; turbulence intensities in front-side eyewall region are greater than those in back-side eyewall regions both in typhoons and hurricanes; the ratio between longitudinal integral scale and lateral integral scale, [Formula: see text], is scattered, but the ratio between longitudinal integral scale and vertical integral scale, [Formula: see text], is closer both in typhoons and hurricanes; the gust factor in typhoon Hagupit is 1.25 over open sea surface and 1.42 over open flat terrain; the peak factor is about 2.4.
Highlights
Typhoons frequently make landfall in South China each year and cause severe structural damages with attending serious economic and personnel loss.[1]
In the boundary layer of a tropical cyclone, mean and turbulent wind fields have characteristic flow structures driven by buoyancy and shear that are observed to vary significantly as the radius increases from wind eye to outer-vortex regions, and to render the wind characteristics different from synoptic winds.[3]
In addition to the structural characteristics, sudden change in wind speeds and directions along the radial axis of the storm wind field may lead to large excursions in wind speeds at ground level as the sharp interface/eyewall meets the ground and the radial pressure gradient associated with the turbulence gradient drives an inward flow, which stimulates roll structures that are aligned with the swirling flow by the combined convective and dynamic instabilities.[3,4,5,6]
Summary
Typhoons frequently make landfall in South China each year and cause severe structural damages with attending serious economic and personnel loss.[1]. Through a comparative study of multi-platform measurements in typhoons and/or hurricanes, it is meaningful to conclude the wind characteristics in tropical cyclones to advance the structural design in cyclone-prone regions. The ‘‘Wind characteristics’’ section presents a comparative analysis of wind characteristics such as mean wind speed and direction, friction velocity, aerodynamic roughness length, drag coefficient, turbulence intensity, integral scale, gust factor, and peak factor in typhoon Hagupit and other tropical cyclones reported in literatures. The data acquisition system measures three-dimensional (3D) wind speed and direction at 60 m height using Gill WindMaster Pro ultra-anemometer at a sampling frequency of 10 Hz and collects barometric and temperature at 8 m height using NRG BP-20 barometer and NRG #110S temperature sensor, respectively. 10min Mean wind speed 䠄㼙 㻛㼟䠅 10min Mean wind direction㻔o䠅 10min vertical wind direction 䠄o䠅 䠄
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