Experimental analysis of air exchange mechanisms between indoor environments under human and climatic forcings

Airflow dynamics in indoor environments play a crucial role in pollutant dispersion and the overall indoor microclimate. This study experimentally investigates air exchange processes between two interconnected rooms under two distinct driving mechanisms: human motion, specifically the “pump effect” generated by a person walking through a doorway, and wind-induced interactions between indoor and outdoor spaces. To capture these phenomena, two reduced-scale experimental models were developed based on Reynolds number similarity. The first, operating with air inside a wind tunnel, explored the effects of external wind, window configurations, and pressure differentials on inter-room airflows. Hot-wire anemometry measurements provided a detailed characterization of turbulence and flow rates, revealing a power-law relationship between the volumetric flow rate and the Euler number, with an observed exponent of 0.39. The second model, a water-filled tank, enabled detailed visualization of turbulent flow structures generated by human motion through the use of ultrasonic velocimetry and in particular Particle Image Velocimetry (PIV). The results highlighted how walking speed and imposed recirculation flows influence air exchange, with specific flow rates identified that minimize crosscontamination between rooms. The findings offer valuable insights for the design of localized ventilation strategies aimed at reducing backflow and improving indoor air quality. Future work will extend the experimental database to support the calibration and validation of computational fluid dynamics (CFD) models, enabling accurate prediction of recirculation and stagnation zones and optimizing HVAC system design.