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不同强风样本湍流特性参数的计算分析
Turbulent Characteristic Parameter of Different Strong Wind Samples
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摘要: 在结构风工程中, 风湍流统计参数计算的正确与否直接影响到风荷载的计算精度。在实际风参数计算与分析中, 多选用风速较大的样本资料, 但过分强调大风可能产生不合理的计算结果。利用超声风速仪瞬时风速观测资料, 分别划分成相对强风和持续强风样本, 计算并比较其湍流统计特性参数, 发现湍流统计参数特性值 (湍流度、阵风因子、摩擦速度等) 与风速大小并不能很好匹配, 有时风速不大但其湍流特性值却很大, 反之也然。研究表明:选取的湍流风资料样本或统计方法不同, 都会影响风特性参数的计算结果, 进而影响到风荷载计算的精度。这一结果对于提高结构风工程中风参数计算与设计的科学性和合理性具有现实意义。Abstract:
In structure wind engineering, the accuracy of wind turbulent characteristic parameter is extremely important to the calculation of wind load of large structures. In the actual wind observation and analysis, the gale data are generally used to analyze the turbulent parameter characteristics, and more attentions are caught by the strong wind such as typhoon in coastal area. The calculation of wind turbulent characteristic parameter may be disturbed by an excessive attention given to the strong wind data. Moreover, the precision in the calculation of wind load may decline. In order to comprehend the impact of different strong wind samples upon the calculation of turbulent characteristic parameter values, an analysis and a comparison between two groups of wind speed samples are made. In the experiment, the CSAT3D three dimensional supersonic anemometer is used to observe the instantaneous wind speed from June to September in 2005 on the no rthern coast of Jiaozhou Gulf. About 605 hours effective wind observation data or 3631 subsamples are obtained in the experiment and divided into 10-min time step. The subsamples are divided into two groups according to different wind speed. One is called continual strong wind sample, in which the average wind speed during 10 minutes of each subsample is more than 8 m/s and the duration is more than 30 minutes. The other is called relative strong wind sample, in which the average wind speed of the subsamples is not always more than 8 m/s. The turbulent characteristic parameters of the two wind sample groups are calculated and a comparison between the two groups is made accordingly. It shows that though the average wind speed of continual strong breeze samples is about 37.6% more than that of relative strong wind samples, the average turbulent intensity of the relative strong breeze is 18%—23.5% smaller than that of the comparative strong wind samples, and the former average gust factor is more than 10%smaller than the latter, where as the former average friction velocity is 50% more than the latter. These results show that the value of wind turbulent characteristic parameter doesn't match the wind velocity well. Sometimes the wind velocity is small but its turbulent characteristic parameter value is big and vice versa. So, different wind velocity sample or different statistical methods may affect the calculation results of wind turbulent characteristic parameter.The calculation of wind turbulent characteristic parameter may be affected by an excessive attention given to the strong wind data. Moreover, the precision in the calculation of wind load may decline.
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图 2 平均湍流度与平均风速的关系
Fig. 2 The relationship between average turbulence intensity and average wind speed
图 3 平均阵风因子与平均风速的关系
Fig. 3 The relationship between average gust factor and average wind speed
图 4 平均摩擦速度平方与平均风速的关系
Fig. 4 The relationship between average friction velocity and average wind speed
表 1 60 m高度风观测样本平均风速
Table 1 The average wind speed observed with CSAT3D at 60-meter height
表 2 强风和持续强风样本的平均湍流度 (I) 和阵风因子 (G)
Table 2 The average turbulence intensity (I) and gust factor (G) of the two sample groups
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