A numerical method based on Computational Fluid Dynamics is applied for a preliminary study of the relationship between driving rain and building envelope pathology (facade surface disfigurement). The study is conducted for the case of the ceramic brick facade of a low-rise office building. It will be shown that the numerical method can be used to explain disfigurement patterns that are caused by direct driving rain impingement. Figure 1. Surface soiling patterns at the ceramic brick facade of a low-rise office building. Until recently, information on driving rain on buildings was gathered by employing either an experimental or a semi-empirical approach. As research efforts continued to reveal the inherent complexity of the problem, researchers realized that further achievements were to be found through numerical analyses. In the past decade, Computational Fluid Dynamics (CFD) has made its introduction in the area. A number of researchers have employed CFD to study the trajectories of raindrops in the calculated wind flow pattern around a building and to determine the driving rain amount falling onto the building facade (Choi 1993, Wisse 1994, Sankaran & Paterson 1995, Lakehal et al. 1995, Karagiozis et al. 1997, van Mook et al. 1997, van Mook 1999, Hangan 1999, Etyemezian et al. 2000). Based on their investigations, a practical numerical simulation method for driving rain has been developed (Blocken & Carmeliet 2000a, 2000b). The method allows the calculation of both the spatial and temporal distribution of driving rain on buildings based on generally available climatic data (wind speed, wind direction, rainfall intensity). It has been verified and found to yield fairly accurate results for the case of a low-rise building and for different rain events (Blocken & Carmeliet 2000a, 2002). In this paper, the numerical model is employed to examine and explain the observed staining pattern p3. A brief review of the numerical model will first be given in section 2. In section 3, the case study will be outlined, computed and analysed.
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