A comprehensive evaluation of ventilation performance in urban buildings with different opening configurations

The efficiency of natural ventilation in cross-ventilated buildings is significantly influenced by the positioning of openings. In sheltered conditions, where building configurations generate complex flow interactions, indoor air distribution and ventilation efficiency can be substantially impacted. This study investigates the influence of various opening positions on ventilation performance in two representative urban layouts: square (SQ) and staggered (ST) building arrays. Computational fluid dynamics (CFD) simulations were performed using the renormalization group k-ε (RNG) closure model. The evaluation of ventilation performance is conducted by three principal indices: ventilation rate, age of air, and air exchange efficiency, enabling a comprehensive assessment of indoor air quality. The results indicate that both ventilation rate and air exchange efficiency are significantly influenced by the combination between opening locations and array configurations. In both array layouts, positioning openings at elevated positions on the windward and leeward facades consistently improves the dimensionless ventilation rate by 2 to 3 times compared to other opening arrangements. A similar trend is observed in air exchange efficiency, attaining 61% for SQ array and 73% for ST array. This is attributed to a deeper penetration of air into the building envelope and enhanced internal mixing prior to leaving the area. Furthermore, under SQ array, placement of both openings in the lowest region of the facades should be avoided as it leads to poor ventilation rate and decreased air exchange efficiency. These findings highlight the importance of openings position in optimizing natural ventilation strategies for buildings situated in sheltered urban environments.