PARAMETERS AFFECTING THE INTENSITY OF WIND-DRIVEN RAIN ON THE FRONT FACE OF A BUILDING

In the weathertightness design of building envelope, it is important t o know the amount of rain water impinging on the faces of a building. Wind-driven rain around buildings is a complex phenomenon, and the int ensity of wind-driven rain on a building face is affected by many para meters. The characteristics of the approaching wind and rain are impor tant parameters. The interactions between wind, rain and the building are also expected to have strong effect on the wind-driven rain intens ity. This paper identifies the parameters affecting the intensity of w ind-driven rain impinging onto the front face of a building and invest igates how the intensity is affected. It examines each phase of the pr ocess and their governing parameters which can be grouped into the fol lowing areas. They are (a) rainfall characteristics (drop size distrib ution, intensity), (b) wind speed, (c) building geometry and (d) stati stics of the co-occurrence of wind and rain. A computational fluid dyn amics model is set up and the wind flow pattern around a building, the raindrop trajectories and the wind-driven rain intensity on the front face of a building are calculated. This model is used for the evaluat ion of the effects on the wind-driven rain intensity due to the variou s parameters. The findings indicated that while wind speed, rainfall i ntensity and building geometry all play a part in effecting the wind-d riven rain intensity, the design intensity is governed by the statisti cs of the co-occurrence of wind and rain.