Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds...Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.展开更多
Based on one year gradient wind data and the wind data of a strong typhoon observed by three meteorological towers located on the coast and at the inshore sea,the underlying surfaces of the meteorological towers were ...Based on one year gradient wind data and the wind data of a strong typhoon observed by three meteorological towers located on the coast and at the inshore sea,the underlying surfaces of the meteorological towers were classified and the roughness lengths were calculated quantitatively.On the basis of strong wind characteristic representative assessment and sample selection on the wind data of strong typhoon Hagupit,the gust factor variation characteristics of tropical cyclones under different underlying surfaces were analyzed.The observed fact and variation rule were found as follows:1) The roughness lengths under neutral atmospheric condition which were calculated using logarithmic wind profile fitting based on the observation data can describe the slight change of the underlying surface objectively.2) The gust factor of strong typhoon wind didn't have variation trends with wind speed.But the variation amplitude of the gust factor was rather large over rough underlying surface which had pronounced effect on the numerical design of structural engineering.3) The variation of the gust factor with height satisfied power law or logarithmic law.The power law fitting was more suitable for smooth underlying surface while the logarithmic fitting was better over rough underlying surface.4) The observation data also suggested that the relationship between gust factor and roughness length can be described by power or linear equation.5) The gust factor observed in this typhoon case was different from the gust factor recommended by WMO:The gust factor of the offshore wind came from rough underlying surface was higher than the value recommended by WMO while the gust factor of the onshore wind came from smooth underlying surface is less than the WMO recommended value.展开更多
Using high-frequency onshore wind data from four different heights of a coastal tower,the variations in gust factor with turbulence intensity,height and wind speed were studied under typhoon conditions.The gust factor...Using high-frequency onshore wind data from four different heights of a coastal tower,the variations in gust factor with turbulence intensity,height and wind speed were studied under typhoon conditions.The gust factor increases with increasing turbulence intensity and,most often,can be described by a linear relationship with the turbulence intensity.The gust factor decreases with height and is relatively small compared with those presented in the national codes and other studies.A value of 2.5 is acceptable for the peak factor,which is close to the recommended value of the national code in China.The gust factor increases with increasing wind speed and is also affected by the wind direction.The gust factor has a value to that of previously published results when the wind flows roughly perpendicular to the shoreline,and has a smaller value when the wind flows roughly parallel to the shoreline.The phenomenon is caused by the confinement of shoreline on the sea wave development.Sea waves tend to propagate normal to the shoreline because of the refraction effect.As a result,a shorter roughness length exists in the parallel direction to the shoreline.It can be further explained by the weakness in the momentum flux exchange between the air and sea based on the wave form drag theory when the wind flows parallel to the shoreline.展开更多
基金Projects(51378396,51678452,51708074,2014M560706)supported by General Program of National Natural Science Foundation of ChinaProject(2014M560706)supported by the China Postdoctoral Science Foundation
文摘Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. 90715031, 40775071) the National Special Re-search Fund for Non-Profit Sector of China Ministry of Science and Tech-nology (Grant No. GYHY200806012)
文摘Based on one year gradient wind data and the wind data of a strong typhoon observed by three meteorological towers located on the coast and at the inshore sea,the underlying surfaces of the meteorological towers were classified and the roughness lengths were calculated quantitatively.On the basis of strong wind characteristic representative assessment and sample selection on the wind data of strong typhoon Hagupit,the gust factor variation characteristics of tropical cyclones under different underlying surfaces were analyzed.The observed fact and variation rule were found as follows:1) The roughness lengths under neutral atmospheric condition which were calculated using logarithmic wind profile fitting based on the observation data can describe the slight change of the underlying surface objectively.2) The gust factor of strong typhoon wind didn't have variation trends with wind speed.But the variation amplitude of the gust factor was rather large over rough underlying surface which had pronounced effect on the numerical design of structural engineering.3) The variation of the gust factor with height satisfied power law or logarithmic law.The power law fitting was more suitable for smooth underlying surface while the logarithmic fitting was better over rough underlying surface.4) The observation data also suggested that the relationship between gust factor and roughness length can be described by power or linear equation.5) The gust factor observed in this typhoon case was different from the gust factor recommended by WMO:The gust factor of the offshore wind came from rough underlying surface was higher than the value recommended by WMO while the gust factor of the onshore wind came from smooth underlying surface is less than the WMO recommended value.
基金supported by the National Key R&D Program of China (Grant No.2023YFC3008501)the Shanghai Science and Technology Commission Project (Grant No.23DZ204701)the Science and Technology Research and Development Project of China Construction Eighth Engineering Division Corp.,LTD. (Grant No.2022-Q-03).
文摘Using high-frequency onshore wind data from four different heights of a coastal tower,the variations in gust factor with turbulence intensity,height and wind speed were studied under typhoon conditions.The gust factor increases with increasing turbulence intensity and,most often,can be described by a linear relationship with the turbulence intensity.The gust factor decreases with height and is relatively small compared with those presented in the national codes and other studies.A value of 2.5 is acceptable for the peak factor,which is close to the recommended value of the national code in China.The gust factor increases with increasing wind speed and is also affected by the wind direction.The gust factor has a value to that of previously published results when the wind flows roughly perpendicular to the shoreline,and has a smaller value when the wind flows roughly parallel to the shoreline.The phenomenon is caused by the confinement of shoreline on the sea wave development.Sea waves tend to propagate normal to the shoreline because of the refraction effect.As a result,a shorter roughness length exists in the parallel direction to the shoreline.It can be further explained by the weakness in the momentum flux exchange between the air and sea based on the wave form drag theory when the wind flows parallel to the shoreline.
