横风环境下方形建筑迎风面雨滴收集率特性分析

Analysis of catch ratio distribution on windward facade of a cubic building under a crosswind environment

现有建筑风驱雨研究主要关注不同环境和建筑外形条件下,建筑表面风驱雨量的分布结果,但缺乏对风驱雨量分布产生原因的分析。利用有限区域计算方法,对典型条件下方形建筑迎风面收集率分布进行计算,分析了雨滴轨迹包络区域的变化规律,说明了收集率分布的产生原因。结果表明,从轨迹起点平面至终点平面,轨迹包络区域存在拉伸和扭转2种效应。在风向角为0°、参考风速为10 m/s时,高度和宽度方向拉伸率均呈现“上小下大”、“两侧小中间大”的特点。高度方向边界扭转角呈现从中间到两侧逐渐增大的趋势,宽度方向边界扭转角呈现从角点到中间区域逐渐减小的趋势。随参考风速增大,高度方向拉伸率由正变负,宽度方向拉伸率逐渐减小,高度方向扭转角在靠近地面区域逐渐增大、在建筑上部逐渐减小,宽度方向扭转角在靠近建筑顶部区域逐渐增大、在建筑下部逐渐减小。风向角为30°时,从上风侧到下风侧,高度方向拉伸率、高度和宽度边界扭转角均逐渐增大,宽度方向拉伸率则从两侧到中间逐渐增大。研究结果为分析建筑外形对收集率分布的影响和建筑防雨结构设计提供了进一步的理论依据。

Previous researches on wind-driven rain on buildings mainly focus on wind-driven rain distribution on the facades under different environmental conditions and building geometries,but few researchers have analyzed the cause of the distribution.Employing the finite panel method,the catch ratio distribution on the windward facade of a cubic building is calculated,and the cause of the distribution is explained by analyzing the envelop regions bounded by the raindrop trajectories.Results indicate that there are two effects exist in the transformation of the envelop regions from the starting plane to the ending plane,which are named the stretching effect and the distortion effect.When the wind direction angle is 0°and the reference wind speed is 10 m/s,the stretching rates along the height direction and the spanwise direction both reduce from the bottom of the building to the top and middle to the sides.While the absolute distortion angles of the boundaries along the spanwise direction drop from the building's corners to the middle,their absolute values along the height direction increase from the building's center to its sides.As the reference wind speed increases,the stretching rates along the height direction alter from positive values to negative values,and the stretching rates along the spanwise direction decrease.In the spanwise direction,the distortion angles of the borders increase near the top and decrease near the bottom of the building,while the distortion angles of the boundaries along the height direction increase near the ground and decrease near the top of the building.When the wind direction angle is 30°,the stretching rates along the height direction increase from the upwind side to the downwind side,as well as the distortion angles of the boundaries along the height and spanwise directions.Moreover,the stretching rates along the spanwise direction increase from the sides to the middle.The results provide theoretical bases for further investigating the influence of building layouts on the catch ratio distribution,and designing the rain shielding structures of buildings.