三峡库区青草背长江大桥桥位风速非平稳特性研究

为从定量上描述和评价山区峡谷风场的非平稳程度，利用三峡库区青草背长江大桥桥位处实测风速序列，分别采用轮次检验法和希尔伯特（Hilbert）变换分析了实测风速序列在幅值和频率上的非平稳程度，探讨了风速样本时长和窗口时距对基于Hilbert变换的非平稳度指标的影响，并与西堠门大桥桥位处12月份期间实测风速记录进行对比，实现了山区峡谷风的非平稳特征的定量评价。结果表明：非平稳度值可反映出风速序列在不同频率成分上的非平稳特性，且风速频率越高非平稳度指标越大，同时非平稳度值随风速样本总时长的增大、窗口时距的增大而减小；相比西堠门桥位处风速，青草背长江大桥桥位处山区风风场在幅值和频率均表现出更强的非平稳特性，且短时距高频段的风速分量非平稳特征更为明显；当某段风速序列在给定的窗口时距下的非平稳度值超过良态风速相应的非平稳度极值后，可认为该段风速序列具有较强的非平稳特征。

Field measurement of non-stationary characteristics at site of Qingcaobei Yangtze River Bridge in Three Gorges

In order to quantitatively describe and evaluate the non-stationary characteristics of gorge winds, a series of wind velocities were obtained by field measurements at the site of Qingcaobei Bridge located in Three Gorges. The non-stationary characteristics in time and frequency domain of those gorge winds were analyzed by run test method and Hilbert transform. The effects of sample length and window length on non-stationary index obtained by Hilbert transform were also discussed. A quantitative evaluation method for non-stationary property of mountain areas wind was proposed. It is shown that the non-stationary characteristics of wind in frequency domain can be evaluated by non-stationary index, which increases with the increasing of sample length, and decreases as the time interval becomes longer. Time series of wind velocities obtained at Qingcaobei Bridge site exhibit significant nonstationarity in frequency and amplitude compared with those of Xihoumen Bridge, and the non-stationary properties of wind components with higher frequency and shorter sample length were more remarkable. It can be concluded that a time series of wind velocity can be identified as non-stationary if the index is greater than its extreme value with the same time interval of normal wind.