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

• WWC enables easy retrofit with minimal internal structural modifications. • Separate inlet-exhaust design ensures consistent airflow in WWC. • WWC achieved up to 430% higher airflow velocities than single-sided ventilation (SSV). • WWC shows robust ventilation at challenging angled wind directions (45°, 90°). • Best turbulence model (k-ε RNG) showed lowest prediction errors (MAPE 4.6% at 45°). The rapid urbanisation and increasing density of urban areas have driven the construction of multi-storey 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, resulting in inadequate airflow and stagnant zones. Despite advancements, literature shows 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-storey buildings. Unlike conventional systems, the WWC features externally mounted, separate inlet and exhaust pathways that capitalise on wind-induced pressure differences and facilitate consistent airflow through the building irrespective of wind direction. To evaluate the performance of the WWC, this study employs combined atmospheric boundary layer wind tunnel experiments and computational fluid dynamics simulations under varying wind angles and speeds. Results showed significant improvements with the WWC system compared to SSV, achieving up to 430 % greater average indoor airflow velocity at 0° wind direction and U ref = 3.82 m/s, and maintaining velocities up to four times higher at increased wind speeds (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 turbaulence models, the k-epsilon RNG model exhibited 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-storey buildings.