青藏高原西藏区域近地层大风过程脉动风特性研究

A study on fluctuating wind characteristics during strong wind processes in the surface layer over the Qinghai-Tibet Plateau, Xizang region

  • 摘要: 针对青藏高原西藏区域(后文简称“西藏高原”)近地层大风脉动特性研究不足的问题,本文利用浪卡子和狮泉河两站超声波风速实测资料,选取10 min平均风速大于8 m/s的大风样本,基于数据统计分析研究了西藏高原宽谷湖盆和山谷地形B类地貌条件下的脉动风特征。结果表明:顺风向和横风向平均湍流强度分别为0.23和0.21,平均阵风因子分别为1.52和0.45,整体脉动强度低于沿海台风区,其中顺风向湍流强度和阵风因子与美国ASCE规范推荐值较为接近;顺风向和横风向平均积分尺度分别为111 m和113 m,其中顺风向积分尺度更接近日本规范推荐值;顺风向脉动风速功率谱与von Kármán谱吻合度最高。此外,提出了适用于该类地形的阵风因子-湍流强度关系修正模型以研究该类地形的脉动风演化规律。结果发现,主导来流方向区间内湍流强度与阵风因子随风速增大显著减小,积分尺度表现出明显的方向依赖性。整体来看,西藏高原宽谷湖盆和山谷地形B类地貌条件下的脉动风参数具有明显的区域特征。本文研究可为西藏高原近地层建筑结构抗风设计提供参考。

     

    Abstract: To address the insufficient research on near-surface gale fluctuation characteristics in the Qinghai-Tibet Plateau, Xizang Automous Region, China (hereafter "Xizang Plateau"), this study utilizes ultrasonic anemometer data from two stations, Langkazi and Shiquanhe. Wind samples with a 10-minute average wind speed exceeding 8 m/s are selected. Based on statistical analysis, the fluctuating wind characteristics under type B terrain conditions (wide-valley lake basin and valley terrain) in the Xizang Plateau are investigated. The results show that the average turbulence intensities in the along-wind and across-wind directions are 0.23 and 0.21, respectively, and the average gust factors are 1.52 and 0.45, respectively. The overall fluctuation intensity is lower than that in coastal typhoon areas. The along-wind turbulence intensity and gust factor are close to the recommended values of the ASCE 7-22 of the United States. The average integral length scales in the along-wind and across-wind directions are 111 m and 113 m, respectively, with the along-wind integral length scale being closer to the recommended value of the AIJ-RLB-2004. The power spectrum of along-wind fluctuating wind speed shows the highest consistency with the von Kármán spectrum. Furthermore, a modified model for the relationship between gust factor and turbulence intensity applicable to such terrain areas is proposed to investigate the evolution laws of the fluctuating wind. The results show that, within the dominant inflow direction range, turbulence intensity and gust factor significantly decrease with increasing wind speed, while the integral length scale exhibits a clear directional dependence. Overall, the fluctuating wind parameters under type B terrain conditions in the Xizang Plateau show distinct regional characteristics. The findings can serve as a reference for wind-resistant design of building structures in such regions.

     

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