非平稳非高斯湿下击暴流风雨荷载的模拟
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摘要
为模拟湿下击暴流风雨荷载,使用时变平均风速和调制的kaimal谱数值模拟具有非平稳非高斯特征的下击暴流脉动风速。从模拟结果可以看出,模拟的脉动风速相关函数明显具有时变的特征,而且瞬时相关函数均与目标函数吻合,因此模拟的脉动风速具有非平稳的目标特性;与此同时,在任意时刻,目标函数也与模拟的脉动风速概率密度函数吻合,表明模拟的脉动风速也具有非高斯的目标特性。因此,所采用的非平稳非高斯过程模拟方法有效可行。针对雨滴冲击荷载,首先对单个雨滴运动分析,推导出单个雨滴的冲击力,进而运用单位体积雨滴谱将单个雨滴冲击扩展到大量雨滴的冲击状态。结果表明,风速对雨滴冲击荷载的影响大,雨荷载变化趋势基本与风速一致,说明湿下击暴流的雨滴冲击作用主要由风速拖拽所致;此外,通过改变降雨强度发现,随着降雨强度增大,雨滴冲击力的变化趋势几乎不变,但峰值增大。
In order to numerically simulate the downburst accompanied with rain,the non-stationary non-Gaussian fluctuating wind speed is generated using the time-varying average wind speed and the modulated kaimal spectrum.Analysis of the results shows that the correlation function of the simulated fluctuating wind speed sample possesses the time-varying characteristics,and the instantaneous correlation function is consistent with the corresponding targets,meaning that the simulated fluctuating wind velocity has the targeted non-stationary characteristics;simultaneously,the probability density function agrees with the objective function,implying that the simulated fluctuating wind speed possesses the targeted non-Gaussian trait.Hence,the proposed simulation method is effective and feasible for the non-stationary non-Gaussian stochastic process.In view of the impact load of raindrop,the impact force of a single raindrop is derived from the motion analysis of a single raindrop.Further,the impact of a single raindrop is extended to the impact of a large number of raindrops using the unit volume raindrop spectrum.Analysis of the results indicates that the wind speed has a great influence on raindrop impact load and the trend of rain load is basically consistent with that of the wind speed,thus implying the impact of raindrops of downburst is mainly caused by its wind speed drag.Likewise,with the increase of rainfall intensity the change tendency of raindrop impact force is practically unchanged,but its peak increases.In addition,by changing the parameter of rainfall intensity,it is found that with the increase of rainfall intensity,the change trend of raindrop impact force is almost invariable,but the peak value increases.
In order to numerically simulate the downburst accompanied with rain,the non-stationary non-Gaussian fluctuating wind speed is generated using the time-varying average wind speed and the modulated kaimal spectrum.Analysis of the results shows that the correlation function of the simulated fluctuating wind speed sample possesses the time-varying characteristics,and the instantaneous correlation function is consistent with the corresponding targets,meaning that the simulated fluctuating wind velocity has the targeted non-stationary characteristics;simultaneously,the probability density function agrees with the objective function,implying that the simulated fluctuating wind speed possesses the targeted non-Gaussian trait.Hence,the proposed simulation method is effective and feasible for the non-stationary non-Gaussian stochastic process.In view of the impact load of raindrop,the impact force of a single raindrop is derived from the motion analysis of a single raindrop.Further,the impact of a single raindrop is extended to the impact of a large number of raindrops using the unit volume raindrop spectrum.Analysis of the results indicates that the wind speed has a great influence on raindrop impact load and the trend of rain load is basically consistent with that of the wind speed,thus implying the impact of raindrops of downburst is mainly caused by its wind speed drag.Likewise,with the increase of rainfall intensity the change tendency of raindrop impact force is practically unchanged,but its peak increases.In addition,by changing the parameter of rainfall intensity,it is found that with the increase of rainfall intensity,the change trend of raindrop impact force is almost invariable,but the peak value increases.
引文
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[15] Liang J W,Chaudhuri S R,Shinozuka M.Simulation of nonstationary stochastic processes by spectral representation[J].Journal of Engineering Mechanics,2007,133(6):616-627.
[16] Marshall J S,Palmer W M.The distribution of raindrops with size[J].Journal of Meteorology,1948,5(4):165-166.
[2] 张文福,谢丹,刘迎春,等.下击暴流空间相关性风场模拟[J].振动与冲击,2013,32(10):12-16,35.(ZHANG Wen-fu,XIE Dan,LIU Ying-chun,et al.Simulation of downburst wind field with spatial correlation[J].Journal of Vibration and Shock,2013,32(10):12-16,35.(in Chinese))
[3] Li J H,Li C X.Simulation of non-Gaussian stochastic process with target power spectral density and lower-order moments [J].Journal of Engineering Mecha-nics,2012,138(5):391-404.
[4] 曾岩,李刚.非高斯随机激励下滞迟系统响应与首次穿越失效[J].计算力学学报,2014,31(1):13-17.(ZENG Yan,LI Gang.Response and first-passage failure of hysteretic system under non-Gaussian random excitation[J].Chinese Journal of Computa-tional Mechanics,2014,31(1):13-17.(in Chinese))
[5] 何军,寇新建.非高斯结构首次超越分析的概率模型[J].计算力学学报,2007,24(1):64-68.(HE Jun,Kou Xin-jian.Probabilistic model for the first passage of Non-Gaussian structures[J].Chinese Journal of Computational Mechanics,2007,24(1):64-68.(in Chinese))
[6] Puig B,Akian J L.Non-Gaussian simulation using Hermite polynomials expansion and maximum entropy principle[J].Probabilistic Engineering Mecha-nics,2004,19(4):293-305.
[7] Grigoriu M.Simulation of stationary non-Gaussian translation processes[J].Journal of Engineering Mechanics,1998,124(2):121-126.
[8] Li J H,Li C X,He L,et al.Extended modulating functions for simulation of wind velocities with weak and strong nonstationarity[J].Renewable Energy,2015,83:384-397.
[9] Ge H,Chiu V,Stathopoulos T.Effect of overhang on wind-driven rain wetting of facades on a mid-rise building [J].Building and Environment,2017,118:234-250.
[10] 李宏男,任月明,白海峰.输电塔体系风雨激励的动力分析模型[J].中国电机工程学报,2007,27(30):43-48.(LI Hong-nan,REN Yue -ming,BAI Hai-feng.Rain-wind-induced dynamic model for transmission tower system[J].Proceedings of the Chinese Society for Electrical Engineering,2007,27(30):43-48.(in Chinese))
[11] 王辉,陈雨生,曹洪明,等.组合布局对建筑立面风驱雨分布影响特性的数值分析[J].土木工程学报,2016,49(12):27-34.(WANG Hui,CHEN Yu-sheng,CAO Hong-ming,et al.Numerical simulation for influence of combination layout on wind-driven rain distribution on building facades[J].China Civil Engineering Journal,2016,49(12):27-34.(in Chinese))
[12] 张丽.土楼夯土墙风雨撞击荷载研究[D].华侨大学,2013.(ZHANG Li.The Research of the Impact Load of Rain Induced Wind on Rammed Earth Wall of Earth Building[D].Huaqiao University,2013.(in Chinese))
[13] 李锦华,吴春鹏,陈水生.下击暴流非平稳脉动风速数值模拟[J].振动与冲击,2014,33(14):54-60.(LI Jin-hua,WU Chun-peng,CHEN Shui-sheng.Simulation of non-stationary fluctuating wind velocity in downburst[J].Journal of Vibration and Shock,2014,33(14):54-60.(in Chinese))
[14] Priestley M B.Power spectral analysis of non-sta-tionary random processes[J].Journal of Sound and Vibration,1967,6(1):86-97.
[15] Liang J W,Chaudhuri S R,Shinozuka M.Simulation of nonstationary stochastic processes by spectral representation[J].Journal of Engineering Mechanics,2007,133(6):616-627.
[16] Marshall J S,Palmer W M.The distribution of raindrops with size[J].Journal of Meteorology,1948,5(4):165-166.
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