PIV measurement of human thermal convection flow in a simplified vehicle cabin

Understanding of human thermal convection is important in designing an energy-saving ventilation system for a comfortable environment in vehicle cabins. In this study, the thermal convection flow around a passenger inside a small simplified cabin chamber was measured via a 2D particle image velocimetry (PIV) system to provide validation data for numerical simulations and to reveal the development process of human thermal convection flow. The rising convection flow from the legs merged with the convective boundary layer of the trunk at a height of Y = 0.8 m. The rising flow then ascended along the back of the head and reached a maximum velocity of 0.179 m/s at a height of 0.068 m above the head, as limited by the small vehicle cabin. The convective boundary layers were close to the manikin's surface, with thicknesses of 0.042 m and 0.032 m in the front and back of the manikin, respectively. The overall convection flow in front of the manikin (0.220 m) was thicker than that in the back (0.090 m), adding the width of the manikin, which totally resulted in a 0.498 m coverage width in the sagittal direction. The human thermal convection flow exhibited strong unsteady behavior, indicated by the intermittent rising of plumes one after another and the high standard deviation of the instantaneous velocity. The vortexes of the thermal convection flow were identified by the λci criterion, which indicated increasing size and intensity in the region alongside the rising plumes.