Numerical 3D analysis of oscillatory flow in the time-varying laryngeal channel

Three-dimensional flow through an anatomically representative model of the human larynx has been numerically simulated. This model includes the vestibular folds, the vocal cords and the glottic and subglottic areas. Pseudo-time-varying glottic aperture and flow conditions have been considered during quiet breathing, with a peak volume flow rate of 0.75l/s and a frequency of 0.25Hz. Because of the severe constriction, jet-like configurations have been observed. Minor differences have been outlined between the inspiration and expiration profiles. Simulations demonstrated the presence of a backflow region which may extend to 60mm from the glottis at peak inspiration and occupy 20% of the tracheal cross section. Because of its rolling, this backflow region appears in the sagittal plane close to the anterior wall, only one diameter from the laryngeal constriction and extends over about 40mm. The evolution of the streamwise velocity contours and of the corresponding secondary vector plots at six critical stations, including the glottic section, has also been described. A double pair of counter-rotating vortices develops shortly downstream/upstream from the orifice respectively at inspiration/expiration and merges near the frontal plane about 25mm from the glottis. The effect of the incoming flow has been evaluated by including the pharyngeal channel; no major difference has been observed in the computed flow patterns.