云南大理复杂地形上风场的模拟研究

Simulation of Wind on the Complex Terrain of Dali in Yunnan Province

大风是云南地区的主要灾害性天气现象之一,对当地的经济和农业生产以及日常出行都造成不利影响。运用三维大涡模式OpenFOAM研究云南大理白族自治州南部(100.24°N,24.83°E)微环境地形条件下风场的变化规律。结果表明:入口风速为南风时,由于迎风坡地形的强迫抬升使局部风速增大,最大值接近于入口风速的1.5倍。而同时由于山脉的阻碍作用,在山坡背面坡风速则会急剧减小,同时风向也会发生变化,产生尺度较小的涡旋以及不规则的回流。经计算,该地区刮北风时探测点风速相较于入口风速减小,东风时探测点风速略有增加,而西风入口风速条件下观测点风速变化最大,初始入口风速为西风30 m/s时,7200 s后观测点风速在水平方向上的分量最大可达44.55 m/s。

Wind is one of the major disastrous weather phenomena in Yunnan Province,which causes a large impact on local economy and agricultural production.In this study,a three-dimensional large eddy simulation was performed to investigate the wind variation under a complex terrain in the southern part of Dali,Yunnan Province(100.24°N,24.83°E)by an open-sourced software OpenFOAM.The simulation results show that when it is southerly inlet wind,the local wind speed increases due to the forced uplifting caused by the topography,and the maximum value occurring in the computational domain is close to 1.5 times the strength of the inlet wind.Meanwhile,due to the existence of mountains,the wind speed on the leeward slope decreases sharply,and the wind direction changes,leading to the occurrence of many vortices with small scales and irregular reflows.In contrast to that,under a condition of a northerly wind and an easterly wind,the wind speed at the observational site is slightly reduced and increased,respectively.It should be noted that under a westerly inlet wind,the wind speed at the observational site changes the most.When the inlet westerly wind speed is 30 m/s,the wind speed at the observational point along the horizontal direction can reach 44.55 m/s after 7200 s.