Experimental investigation of airflow from various respiratory activities on a partitioned desk in quiescent air

Abstract

The dynamics and characteristics of exhaled airflow under various respiratory activities, injection points, and inclined angles on a partitioned desk in still air were examined using the Particle Image Velocimetry technique. The study revealed that airflow generated by coughing exhibits two distinct regimes: initial movement within the partitioned area and the subsequent formation of an intrusion flow along the wall surface after the airflow impacts the wall. By calculating the entrainment coefficient, the coughing airflow in initial movement was categorized into two phases: the jet phase and the puff phase. Additionally, it was observed that the trajectory of airflow generated during speech are predominantly controlled by the airflow associated with plosive words. Further analysis indicated that, for a single plosive word, the primary factor influencing the spread of airflow is the traveling distance, which is affected by the tilting angle and the height of the injection source. In contrast, the effect of the intrusion flow generated by the pressure of the airflow upon wall impingement was found to be negligible. The study also presented the influenced area of airflow under different scenarios, demonstrating that when airflow under various respiratory activities decelerated to 1 m/s, it could spread to over 30 % of the central area in most experimental cases. This finding highlights the significant impact on the partitioned area before the airflow fully decelerates to ambient velocity (0.2 m/s), offering valuable insights for future investigations into aerosol concentration and infection risk. These results underscore the importance of understanding airflow dynamics in partitioned spaces to inform strategies for mitigating airborne transmission.