Based upon the impinging jet model, the results of Reynolds stress calculated by Reynolds stress model (RSM) were introduced into the spectrum functions proposed by Letchford and Panofsky respectively. With the three-dimensional fluctuating wind velocity field of the thunderstorm downburst obtained from large eddy simulation (LES), both spectrums were validated, and the one which differs a lot was further revised. In combination with random flow generation technique and fast Fourier transform technique, an efficient method for the simulation of three-dimensional fluctuating wind velocity of the thunderstorm downburst was developed, which satisfied the incompressible condition and coherence function. In order to verify its accuracy, some typical points in a specific radial area of the downburst wind field with relatively high horizontal radial wind velocities were chosen. The simulation method mentioned above was employed to get the three-dimensional fluctuating wind velocities point-by-point along the height direction, whose auto-power spectrum functions and time coherence functions were further checked. The results match well with the target values, which implies that the method can simulate the three-dimensional fluctuating wind velocity field of downburst efficiently and precisely．
LOU Wen-juan, WANG Jia-wei, YANG Lun, CHEN Yong. Simulation of three-dimensional fluctuating wind velocity field #br# upon thunderstorm downburst. JOURNAL OF ZHEJIANG UNIVERSITY (ENGINEERING SCIENCE), 2014, 48(7): 1162-1169.
1］ HOLMES J D. Modeling of extreme thunderstorm winds for wind loading of structures and risk assessment ［C］∥Wind Engineering into 21st Century, Proceedings of 10th International Conference on Wind Engineering. Copenhagen: ［s.n.］, 1999: 1409-1415．
［2］ 孙凌峰,郭学良,孙立谭,等. 武汉“6·22”空难下击暴流的三维数值模拟研究［J］. 大气科学,2003,27（6）:1077-1092．
SUN Ling-feng, GUO Xue-liang, SUN Li-tan, et al. A numerical study of the airplane disaster-producing microburst on 22 June 2000 in Wuhan ［J］. Chinese Journal of Atmospheric Sciences, 2003, 27(6): 1077-1092．
［3］ WILSON J W, WAKIMOTO R M. The discovery of the downburst: T.T.Fujitas contribution ［J］. Bulletin of the American Meteorological Society, 2001, 82(1): 49-62．
［4］ KNUPP K R. Numerical simulation of low-level downdraft initiation within precipitating, cumulonimbi: some preliminary results ［J］. Monthly Weather Review, 1989,117:1517-1529．
［5］ STRAKA J M, ANDERSON J R. Numerical simulations of microburst producing storms: some results from storms observed during COHMEX ［J］. Journal of the Atmospheric Sciences, 1993, 50: 1329-1348．
［6］ PROCTOR F H, BOWLES R L. Three-dimensional simulation of the Denver 11 July 1988 microburst-producing storm ［J］. Meteorology and Atmospheric Physics, 1992, 49: 107-124．
［7］ LIN E W, ORF L G, SAVORY E, et al. Proposed large-scale modeling of the transient features of a downburst outflow ［J］. Wind and Structure, 2007, 10: 315-346．
［8］ VERMEIRE B C, ORF L G, SAVORY E. Improved modeling of downburst outflows for wind engineering applications using a cooling source approach ［J］. Journal of Wind Engineering and Industrial Aerodynamics, 2011a, 99(8): 801-814．
［9］ MASON M S, WOOD G S, FLETCHER D F. Numerical simulation of downburst winds ［J］.Journal of Wind Engineering and Industrial Aerodynamics, 2009, 97(11/12): 523-539．
［10］ HJELMFELT M R. Structure and life cycle of microburst outflows observed in Colorado ［J］. Journal of Applied Meteorology, 1988, 27(8): 900-927．
［11］ SPILLANE K T. On the microburst family. Australian wind engineering society ［C］∥ Third Workshop on Wind Engineering.Brisbane:\[s.n.\],1993．
［12］ HOLMES J D, OLIVER S E. An empirical model of a downburst ［J］. Engineering Structures, 2000, 22(9):1167-1172．
［13］ WOOD G S, KWOKA K C S, MOTTERAMB N A, et al. Physical and numerical modeling of thunderstorm downbursts ［J］.Journal of Wind Engineering and Industrial Aerodynamics, 2001, 89(6): 535-552．
［14］ MASON M S, LETCHFORD C W, JAMES D L. Pulsed wall jet simulation of a stationary thunderstorm downburst, part A: physical structure and flow field characterization ［J］. Journal of Wind Engineering and Industrial Aerodynamic, 2005, 93(7): 557-580．
［15］ CHEN L Z, LETCHFORD C W. A deterministic-stochastic hybrid model of downbursts and its impact on a cantilevered structure ［J］. Engineering Structure, 2004, 26: 619-629．
［16］ 刘锡良, 周颖. 风荷载的几种模拟方法［J］. 工业建筑,2005, 35(5): 81-84.
LIU Xi-liang, ZHOU Ying. Numerical simulation methods of wind load ［J］. Industrial Construction, 2005, 35(5): 81-84．
［17］ DEODATIS G. Simulation of ergodic multivariate stochastic processes ［J］. Journal of Engineering Mechanics, ASCE, 1996, 112(8): 778-787.
［18］ CARASSALE L, SOLAR G. Monte Carlo simulation of wind velocity fields on complex structures ［J］. Journal of Wind Engineering and Industrial Aerodynamics, 2006, 94(5): 323-339.
［19］ SENTHOORAN S, DONG D L, PARAMESWARAN S. A computational model to calculate the flow-induced pressure fluctuations on buildings ［J］. Journal of Wind Engineering and Industrial Areodynamics, 2004, 92(13): 1131-1145．
［20］ SMIRNOV A, SHI S, CELIK I. Random flow generation technique for large eddy simulations and particle-dynamics modeling ［J］. Journal of Fluids Engineering, 2001, 123(2): 359-371.
［21］ 杨伦, 黄铭枫, 楼文娟, 等. 高层建筑三维瞬态风场的混合数值模拟［C］∥第十五届全国结构风工程学术会议暨第一届全国风工程研究生论坛论文集. 北京: 人民交通出版社, 2011: 545-548．
YANG Lun, HUANG Ming-feng, LOU Wen-juan, et al. Hybrid simulation of three dimensional fluctuating wind fields around tall buildings ［C］∥15th National Conference on Structural Wind Engineering and Proceedings of the 1st National BBS Graduate Students in Wind Engineering. Beijing: People’s Traffic Press, 2011: 545-548．
［22］ HOLMES J D, HANGAN H M. A forensic study of the Lubbock-Reese downdraft of 2002 ［J］. Wind and Structures, 2008, 11(2): 137-152.
