Investigation of the quasi-periodic airflow oscillation and ventilation performance of an enclosed environment with a jet air supply

Abstract

Unsteady airflows lead to better mixing in ventilated enclosures, facilitating indoor pollutant dispersion and exhausting. In this study, an air jet ventilated enclosure and its flow characteristics were investigated using experimental measurements and computational fluid dynamics simulations, focusing on the quasi-periodic fluctuation of the airflow field and the advantages of such an oscillation pattern for the ventilation efficiency. Starting from a non-converged Reynolds-averaged Navier–Stokes (RANS) simulation, we then used the unsteady RANS method (URANS). As validated by sampling the high-frequency velocity data of representative positions in the jet-ventilated space, the URANS results reflected the unsteady flow characteristics more precisely than the RANS results, further confirming that the supply jet air swung up and down quasi-periodically. The ventilation performance of such an actual quasi-periodic airflow was evaluated by purging a gaseous pollutant from the enclosure, and the results were compared with those in the average steady-state airflow field to showcase the different performance of the unsteady ventilation system.