On the validity of numerical wind-driven rain simulation on a rectangular low-rise building under various oblique winds.

Wind-driven rain (WDR) is one of the most important boundary conditions for hygrothermal building envelope analysis. Although Computational Fluid Dynamics (CFD) simulation of WDR on building facades has been applied intensively in the past decade, validation is still quite limited, and most previous validation efforts have focused either on wind directions perpendicular to the facade or on buildings of complex geometry. This paper addresses CFD simulations of WDR on the west facade of a simple, rectangular low-rise test building for various oblique winds and CFD validation by comparing the simulation results with full-scale measurements. It is shown that overall, fairly accurate results can be obtained, but that the numerical simulations can significantly underestimate the WDR amounts near the downwind edge of the facade when the wind direction is increasingly oblique. These discrepancies are at least partly attributed to the very small impact angles of the raindrops at these facade positions and the resulting inaccuracies in the numerical model