静止型雷暴冲击风作用下列车气动导纳函数试验研究

Experimental study on aerodynamic admittance functions of the train under the stationary thunderstorm downburst wind

为研究静止型雷暴冲击风作用下列车的气动导纳函数,利用雷暴冲击风试验装置模拟雷暴冲击风场,基于刚性模型测压试验,并考虑列车模型对周围风场的影响,测试并分析距雷暴冲击风中心不同径向距离的列车抖振力谱、脉动风速谱以及脉动风速相干函数特性。通过拟合脉动风速相干函数获得考虑顺风向和竖向脉动风速展向相关性的传递函数,识别出考虑脉动风速展向相关性的列车气动导纳函数,并与未考虑脉动风速展向相关性的气动导纳函数进行对比。研究结果表明,当径向距离较小时,如r/D_(j)=0.5时,列车抖振力谱的能量主要集中在极值频率附近的窄带范围内;随着径向距离的增大,列车抖振力谱极值频率附近的能量逐渐向低频部分转移,同时,脉动风速谱的低频部分能量分布逐渐变均匀,而高频部分逐渐符合“-5/3”定律。当列车模型放入风场后,不同测点位置处的顺风向和竖向脉动风速谱的幅值随径向距离而变化,但距列车模型中心2B处的顺风向和竖向脉动风速谱的变化趋势与空风场的较接近。不同径向距离时,脉动风速相干函数都存在峰值,列车的侧向力和升力气动导纳函数在低频部分均趋近于一个常数;当径向距离r/D_(j)=1时,侧向力和升力气动导纳函数的幅值最大,而其他径向距离的侧向力和升力气动导纳函数幅值均基本相同。考虑传递函数后,识别出来的气动导纳函数幅值显著增大,同时高频部分的气动导纳函数幅值随着频率的增加其变化趋势也不同。采用频响函数拟合列车的气动导纳函数时,气动导纳函数低频部分的幅值由系数k决定,同时径向距离越大,拟合参数a、b和k值均越大。

To study the aerodynamic admittance functions of the train under the stationary thunderstorm downburst wind,a thunderstorm downburst wind test device was used to simu⁃late the thunderstorm downburst wind field.Based on the pressure measurement tests on a rigid model,and considering the influences of the train model on the surrounding wind field,the characteristics of buffeting force spectra of the train,fluctuating wind speed spec⁃tra and coherence functions at different radial distances from the center of the stationary thunderstorm downburst wind were tested and analyzed.By fitting the fluctuating wind speed coherence functions,transfer functions considering the spanwise correlation of longitudinal and vertical fluctuating wind speeds were obtained.Then,the aerodynamic admittance func⁃tions of the train considering the spanwise correlation of fluctuating wind speeds were identi⁃fied and compared with those without considering the spanwise correlation of fluctuating wind speeds.The results show that when the radial distance is small,such as r/D_(j)=0.5,the energy of the buffeting force spectra of the train is mainly concentrated in the narrow band near the extreme frequency.With the increase of radial distance,the energy near the extreme frequency of the buffeting force spectra of the train gradually shifts to the low⁃fre⁃quency part.At the same time,the energy distribution of the low⁃frequency part of the fluc⁃tuating wind speed spectra gradually becomes uniform,while the high⁃frequency part gradu⁃ally conforms to the“-5/3”law.When the train model is placed into the wind field,the amplitudes of longitudinal and vertical fluctuating wind speed spectra at different measure⁃ment point positions change with the radial distance,but the trends of longitudinal and ver⁃tical fluctuating wind speed spectra at 2B from the center of the train model are closer to those of the empty wind field.At different radial distances,the fluctuating wind speed co⁃herence functions all have peaks,and the aerodynamic admittance functions of the lateral and lift force of the train tend to be constant in the low⁃frequency part.When the radial dis⁃tance r/D_(j)=1,the amplitudes of aerodynamic admittance functions of the lateral and lift forces are the highest,while the amplitudes of aerodynamic admittance functions of the lat⁃eral and lift forces for other radial distances are basically the same.After considering the transfer functions,the amplitudes of the aerodynamic admittance functions have significantly increased,and the amplitudes of the aerodynamic admittance functions in the high⁃frequency part also change with frequency in a different trend.When the frequency response function is used to fit the aerodynamic admittance function of the train,the amplitude of the low⁃frequency part of the aerodynamic admittance function is determined by the coefficient k.At the same time,as the radial distance increases,the fitting parameters a,b,and k in⁃crease as well.