Investigation of the flow physics in the human pharynx/larynx region

Abstract

This experimental study was carried out to investigate the flow field in the human extra-thoracic airway using the particle image velocimetry technique. The purpose of this study is to understand the physics of the turbulent flow in the pharynx/larynx region. The flow rate was 9 l/min, and the corresponding Reynolds number, based on the inlet condition, was 670. Two thousand images were acquired at each location at a framing rate of 2 Hz. The mean turbulence intensity, turbulent kinetic energy and Reynolds stress fields were calculated. Moreover, the proper orthogonal decomposition method and quadrant analysis were also used for investigating the flow in the pharynx/larynx region. The results showed that the flow is strongly three dimensional and is characterised by re-circulation, jet-like and sink-like mean flows. The pharynx/larynx region is characterised by bursting events (e.g. ejection, sweep and interaction events) particularly in the epiglottal region. These events appear to be responsible for deforming and/or tearing apart the vortical structures. In addition, the major contribution to the Reynolds shear stress comes from the events that mainly burst with or against the flow direction which, in some cases, exceeded 100 % of the inlet velocity.