Investigating Wind-Driven Rain Effects on Buildings with 3D City Building Models: An Analysis of Building Complexity Using Computational Fluid Dynamics

Wind-driven rain (WDR) has significant implications for building performance, including hygrothermal performance, interior damage, and structural cracking. This study focusses on investigating the effects of WDR on buildings using 3D city building models. The utilization of Computational Fluid Dynamics (CFD) allows an accurate computation of the wetting area, facilitating building condition assessment. To address the need for improved building representation, this study proposes the involvement of the building model based on the city building modelling standard. Two building models of different levels of detail (LoD) are employed, namely LoD1.3 and LoD2.3. By comparing wind velocity, pattern, and wetting area, the study examines how building complexity influences the interaction with WDR. The results demonstrate that the complexity of the building significantly influences the calculated wind velocity and pattern, as different building structures and designs are represented in the models. Furthermore, variations in wind parts affect the resulting wetting area, which is closely related to the rain trajectories induced by the wind direction. By focusing on areas with structural differences in building models, the study observes that the wetting area varies according to the diversity of exposed and protected regions. Consequently, it is concluded that different LoDs can lead to different WDR outcomes. Therefore, opting for a higher LoD provides more accurate observations of the WDR. In conclusion, this study highlights the importance of investigating the effects of WDR on buildings using 3D city building models. The analysis of building complexity utilizing Computational Fluid Dynamics offers valuable insights into the impact of WDR on building performance.