戈壁地表野外风速脉动特征

【目的】探究戈壁地表野外风场不同高度风速脉动特征,为进一步湍流情况下风蚀研究奠定基础。【方法】2015年春季在新疆卡拉贝利工程区实测了戈壁地表不同高度瞬时风速,利用统计学方法(标准差、曲线估计等)从风速脉动和脉动强度、湍流度,以及三者与风速之间的关系等角度分析戈壁地表风速脉动特征。【结果】不同高度的瞬时风速和风速脉动在时间序列上变化非常复杂,但变化趋势一致。大风时段(0～50 min),风速脉动幅度非常大,最大接近6 m/s,但90%以上集中在Symbol|A@0～3Symbol|A@ m/s。风速脉动幅度随风速增强而增大,随距地表高度增加而增大。风速脉动概率分布符合高斯分布。不同高度的风速脉动强度与风速均呈一元线性关系,风速越大,风速脉动强度越大。风速脉动强度最大值2.41 m/s。在距地表0～2 m高度内,湍流度在0.14～0.21之间变化,平均约为0.17,湍流强度较高,此高度内湍流度与高度、平均风速无明显关系。【结论】戈壁地表风速脉动具有非平稳性,随风速增强而增大,尤其是大风天气下研究风蚀不能忽略风速的脉动性。

Characteristics of wind velocity fluctuation over Gobi underlying surface

【Objective】This study is to investigate the characteristics of wind velocity fluctuation in the wild area for the theoretical foundation of the research of wind erosion in turbulent flow.【Method】Most previous studies of wind-blown sand were conducted for the wind tunnel, and limited actual wind field data were available because it is difficult to be determined due to poor natural conditions in Gobi area. Therefore, in this study, the instantaneous wind velocities of different height were measured in Gobi surface of Carabeli project area, Xinjiang Uygur Autonomous Region in 2015. Depending on the data, we mainly analyzed the characteristics of wind velocity fluctuation of different heights(0-2 m)from several aspects, that were the wind velocity fluctuation, turbulence intensity, wind velocity fluctuation intensity, and the relationship between them and wind velocity using statistical methods. In addition, the optimal fitting equation was selected by the method of curve estimation in regression analysis.【Result】The variation of instantaneous wind velocity and wind velocity fluctuation of different heights is complex, and their change trends with time are almost similar. In the period of 0-50 min, the instantaneous wind velocity fiercely jumps at the altitude of 40 cm and it tends to be smaller. The amplitude of wind velocity fluctuation is very large, and its maximum value is close to 6 m/s. However, 90% of it is concentrated in the range of∣0-3∣m/s. The probability distribution of wind velocity fluctuation is Gauss distribution. There is a unitary linear relationship between fluctuation intensity and wind velocity. The stronger the wind velocity, the stronger the fluctuation intensity is obtained. The maximum value of wind velocity fluctuation intensity is 2.41 m/s. The turbulence intensity varies between 0.14 and 0.21, and its mean value is about 0.17. It belongs to the high turbulence intensity. No obvious relationship between the height and average wind velocity below 2 m is observed.【Conclusion】The wind velocity fluctuation is non-stationary. As the wind velocity and height increase, the wind velocity fluctuation tends to be stronger in Gobi. The wind velocity fluctuation cannot be ignored when the wind erosion is studied, especially in the windy weather.