土木工程下击暴流风速数值模拟的研究

雷暴天气下击暴流之类的高强风对诸如输电塔这样的晶格状结构具有很大的破坏性。因此,建立可靠合理的下击暴流风速模型来分析这些结构在这种极端风荷载作用下的动力响应是很有必要的。通过运用一些时频分析工具可以发现:下击暴流风速表现出明显的非平稳性。而且,下击暴流非平稳风速时程可以分解为随时间变化的平均风速即时变平均风速与具有一定相关性的随机脉动成分。基于Holmes平均风速模型和Vicroy风速竖向分布模型,使用Deo-datis提出的均匀调制非平稳随机场的模拟方法,数值模拟了雷暴天气下击暴流行进路线上某一固定位置处的竖向分布风速场。在随机脉动成分的数值模拟过程中,引入了三次样条函数插值技术,以减少Cholesky分解的次数,进一步提高了数值模拟雷暴天气下击暴流风速的效率。

Numerical simulations of downburst wind speeds in civil engineering

High intensity winds in many parts of the world are caused by severely convective thunderstorm downbursts, which are responsible for the failures of many slender lattice structures, such as transmission line towers. Therefore, it is essential to build up an applicable and appropriate model to quantitatively assess the safety of these structures subjected to this sort of extreme wind loading through analyzing the corresponding dynamic responses. With the help of time-frequency analysis tools, the non-stationary component embedded in downburst winds can be detected so that downburst winds are characterized as a summation of time-varying mean and coherent fluctuating components. In the present paper, based on Holmes’ empirical model and Vicroy’s vertical profile used to model the deterministic time-varying mean wind speed, the vertical distribution wind velocity field of a definite position in the course of a thunderstorm downburst may be simulated by resorting to the uniformly modulating non-stationary stochastic process approach by Deodatis. In the simulation, the cubic spine interpolation technique is introduced here to reduce the times of Cholesky decomposition so as to further improve the efficiency of the simulation.6748