Investigating the influence of neighbouring structures on natural ventilation potential of a full-scale cubical building using time-dependent CFD

- Ventilation rates are found experimentally and computationally for the Silsoe cube in isolation and irregular array format.
- CIBSE A overestimates building pressure coefficients in urban settings.
- K-ω SST SAS accurately predicts ventilation rates in OpenFoam and Fluent.
- Cubes in centres of arrays obtain pulsing ventilation due to shedding vortices.

Building location and orientation with respect to incident wind angle are important parameters in determining wind-driven natural ventilation. Experimentally measured façade pressures and ventilation rates in the Silsoe cube under single-sided and cross-flow ventilation configurations are compared with CFD simulations conducted in OpenFoam and ANSYS Fluent using a typical linear workflow approach. Eight wind directions are studied with the cube in isolation and in a new staggered nine cube array format. Comparison is made using CIBSE's prescribed ventilation calculation method based on internal/external building pressure differences. Ventilation rate in the isolated cube with single-sided opening was comparatively lower than either of the cross-flow cases, and relationships between air change rate and wind angle were much weaker in the array cases. For the single opening case with the isolated cube, ventilation effectiveness decreases as the wind turns towards the opening due to increased short-circuiting of airflows. Turbulent structures close to windows improve mixing in the array case. Simulations suggest that vortex shedding from up-wind buildings provides pulsating ventilation in both window configurations, which may attenuate the negative effects of upwind flow obstruction.