Simulation of non-stationary fluctuating wind velocity in downburst
LI Jin-hua，WU Chun-peng，CHEN Shui-sheng
1. Department of Civil Engineering, East China Jiaotong University, Nanchang 330013，China； 2. Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong 999077, China
Abstract：Distinct from the atmospheric boundary layer wind, average wind speed of downburst has observable time-varying characteristics, and its fluctuating wind possesses strongly non-stationary characteristics. According to the evolutionary spectrum theory, to realize the effective simulation of non-stationary fluctuating wind needs to establish a non-uniform modulation function of the power spectrum, and an efficient simulation method of non-stationary wind speed. To do this, firstly in this paper the method to create Kaimal non-uniform modulation function is used to obtain other modulation functions of power spectra, such as Davenport, Simiu and Harris, which provide the precondition for simulating non-stationary fluctuating wind. Then, founded on the autoregressive (AR) model to further consider the time variability, a time-varying autoregressive (TAR) model is established, which provides an effectual method for non-stationary wind speed simulation. Finally, based on the precondition and method of the above, the non-stationary fluctuating wind speed in downburst is simulated with considering the time-varying features of average wind speed. The simulation results show: for the non-stationary fluctuating wind velocity of downburst, the cross-correlation weakens along with the distance increases between the different positions, and the amplitude increases with time-dependent average wind speed increases, which coincide with the actual wind field characteristics and indicate the effectiveness of non-uniform modulation function; the power spectrum has obvious time-varying characteristics which match well with the target time-varying spectrum, and the temporal average power spectrum and correlation function are also in agreement with the targets, which involve the efficiency of the method generating non-stationary fluctuating wind of downburst.
2014, Vol. 33 
