Vortex Identification in the Flow Field of Opposed Jet-Vents in Occupied Enclosure

In an occupied enclosure space formed by multiple opposing jet outlets, understanding vortex structures is crucial in controlling the spread of viruses and pollutants. In this study, a scaled model of an occupied enclosed space with opposing jet flows was constructed by incorporating a heated floor as a heat source to create thermal plumes under cooling conditions. A particle image velocimetry (PIV) system was employed to measure the flow field under isothermal and cooling conditions. The identification performance of different vortex identification algorithms was compared by studying the turbulent characteristics of the flow field from the perspective of the vortex. The Liutex vortex identification method was applied to analyze the vortex motion within one oscillation period, revealing distinct strengths in counterclockwise and clockwise directions, with maximum intensities of 50 s^-1 and 110 s^-1, respectively. The study concluded that the motion, merging, and annihilation of vortices influenced the flow field structure with a jet oscillation period of approximately 3.67 s. Owing to the trapping effect of vortices on pollutants, areas of pollutant accumulation can be represented using relative frenquency distribution maps of vortex cores. Despite the unsteady flow field, the vortex distribution remained relatively stable. Specifically, on the left side of the CS4 cross-section, the vortex core appeared at the same point up to 21 times. Under cooling conditions, pollutants are confined to smaller regions, which aids in containing the spread of pollutants.