Wind-driven rain on two parallel wide buildings: field measurements and CFD simulations

Most studies of wind-driven rain (WDR) reported in the literature focus either on isolated buildings or on a particular building in geometrically complex environments. There is a need for experimental and numerical studies for more generic multi-building geometries. The present study reports detailed field measurements and numerical simulations of WDR that are conducted for an idealized geometry with two parallel wide buildings with different heights, located in Dübendorf, Switzerland. The datasets of rain events and WDR measurements with high spatial and temporal resolution are made available online to download and are intended for model development and validation. Numerical simulations are performed with computational fluid dynamics (CFD) based on the 3D steady Reynolds-averaged Navier-Stokes (RANS) equations and an Eulerian multiphase (EM) model for WDR, including the turbulent dispersion of raindrops. The numerical results are validated by comparing the calculated catch ratio values and cumulative WDR amounts with data from the field measurements. The CFD simulations accurately estimate the WDR intensities at the positions of 18 WDR gauges. The average discrepancies between the numerical and experimental results are found to be 6.9% for the rain event on February 20-21, 2014 and 4.9% for the rain event on August 2-3, 2014. In different building configurations, the influences of recirculation regions, sheltering, wind-blocking effect and acceleration of wind determine the WDR distribution on the downstream building. WDR can increase due to recirculation regions and acceleration of wind, while wind-blocking effect and sheltering decrease WDR.status: publishe