Wind-driven rain (WDR) loading on building facades: A state-of-the-art review

Wind-driven rain (WDR), as one of the environmental loads, is an important factor in designing durable and climate-resilient buildings. The negative consequences of moisture intrusion caused by WDR include degradation of surface material, frost damage, salt efflorescence, structural cracking, interior damage, etc. WDR has been extensively studied through experimental measurements, numerical simulations, and semi-empirical methods. The previous WDR studies can be categorized into two areas: the study of WDR loading on buildings and the investigation of facade response to the impinging raindrops. While previous studies have investigated the characteristics of WDR loading on facade, such as the wetting pattern on various building configurations, i.e. stand-alone (isolated), street canyon, building-array, urban area. This review paper synthesizes results from the previous studies and provides a comprehensive summary and comparison of research approaches and their outcomes regarding quantification of WDR loading on building facades. The effect of meteorological and geometrical parameters on the interaction of WDR and buildings has been discussed. A cross-comparison of the WDR results has been performed based on previous experimental, CFD, and semi-empirical studies. The effectiveness of RANS and LES approaches has also been discussed. This paper shows that WDR results depend on the CFD approach selected and on the type of WDR modeling techniques used, i.e. Lagrangian Particle Tracking (LPT), and Eulerian Multiphase (EM). It is important to consider turbulent dispersion for the lower part of the windward facade in the case of high-rise buildings in CFD simulations. Finally, the review highlights potential research gaps in WDR.