Identification of vortical structures inside the human pharynx/larynx region from POD-reconstructed velocity fields

This paper reports an experimental investigation of the vortical structures in the pharynx/larynx region of an idealised human extra-thoracic airway obtained using particle image velocimetry (PIV). The inlet velocity was 0.13?m/s yielding a Reynolds number, based on the inlet condition, of 670. Two thousand images were acquired at each location at a framing rate of 2?Hz. The proper orthogonal decomposition method was applied to the PIV data. Only a few modes were used for POD reconstruction which recovered about 60?% of the turbulent kinetic energy. A vortex identification algorithm was employed to identify and measure properties of the structures. This step was followed by a statistical analysis of the distribution of number, size, and strength of these vortices. The results reveal the formation of a large number of structures identified along two planes in the pharynx/larynx region. This study also revealed an increased strength in the counter-clockwise structures as compared to clockwise structures in the pharynx region. As well, there is some evidence to suggest that the vortical structures, whose axes are perpendicular to the sagittal plane, change their orientation as they proceed further into the laryngeal region.