Stereoscopic PIV Measurements Of The Human Thermal Plume

Abstract

A human thermal plume contributes significantly towards indoor fluid flows. Such flows impact the ventilation system designs like mixing and displacement ventilation. Further, the human thermal plume influences the dispersion of air constituents to and away from the breathing zone. This is also relevant in the transport of respiratory droplets which results in spread of respiratory diseases including COVID-19. One of the general scenarios in many ventilated spaces is the sitting condition which is the focus here. Experiments were performed with a thermal manikin and comparisons were made with a real human. The thermal plume is visualised by Stereoscopic PIV with the visualisation plane located 30 cm above the head parallel to ground. The results presented here show that the thermal plume from a manikin without breathing function have many similarities in the average flow field above the head with the field induced by a real person. The peak velocity observed with the real person is slightly lower than the one of the thermal manikin and the structures of the thermal plumes resemble to some extent in both cases. The real person with breathing or talking revealed a bi-lobe like structure with the secondary lobe due to the breath. The thermal manikin also showed a second lobe which possibly is due to the thermal plume from the legs. Furthermore, the effect due to breathing, speaking, and movement of the real person are analysed. The integral values do not vary with respect to the different situations except for the movement case. The characterizations of these phenomena are important because they cannot be simulated by the manikin, while they affect the extent and strength of the thermal convection flow.