Numerical modeling and wind tunnel testing of a novel wall windcatcher natural ventilation system for multi-floor buildings

The rapid urbanization and increasing density of urban areas have driven the construction of multi-story buildings, intensifying challenges in achieving effective indoor natural ventilation. Traditional ventilation approaches such as single-sided ventilation (SSV) often exhibit limitations, particularly in multi-floor and multi-zone contexts, due to their reliance on single-facade openings, leading to inadequate airflow and stagnation zones. Despite advancements, literature reveals a gap in effectively utilizing natural ventilation systems for consistent airflow across multiple floors, particularly under varied wind orientations. This study introduces a novel wall windcatcher (WWC) ventilation system specifically designed for multi-story buildings. Unlike conventional systems, the WWC features externally mounted, separate inlet and exhaust pathways that capitalize on wind-induced pressure differences and facilitate airflow through the building irrespective of wind direction. To evaluate the performance of the WWC, this study employs a combination of atmospheric boundary layer wind tunnel experiments and computational fluid dynamics (CFD) simulations under varying wind angles and speeds. Results showed significant improvements with the WWC system compared to SSV, achieving up to 5.3 times higher average indoor airflow velocity at 0° wind direction (U_ref = 3.82 m/s), and still achieving up to four times higher velocities at the increased wind speed (U_ref = 7.59 m/s). The WWC consistently reduced stagnation zones and provided more uniform airflow distribution across all floors, particularly evident at challenging wind angles such as 90°, where SSV struggled with stagnation and velocities below 0.05 m/s. Among evaluated turbulence models, the RNG k-epsilon model exhibited the highest accuracy in predicting pressure coefficient, especially at perpendicular wind angles, where other models showed considerably higher discrepancies. This research provides insights and validation for the WWC system, highlighting its potential to advance building ventilation strategies in multi-story buildings.