Coherence at many scales in the vocal tract and jet during speaking

The intricate geometry of an anatomically accurate vocal tract and variations in flow rate develop a wide range of turbulent scales both in the tract and the external jet during breathing and speaking. The "train of puffs" or turbulent pulsed jet complicates the dispersion of aerosolized particles emitted from the mouth during such events. We study the evolution of coherent structures of steady and pulsed jets during speaking using geometrically-resolving large-eddy simulation with the curvilinear immersed boundary method capturing the internal vocal flow and the external speaking jet characteristics of an anatomically accurate vocal tract geometry. Simulations reveal complex coherent structures such as attached and shed vortices and recirculation zones over a wide range. Large vortical features are observed in the glottal region and evolve and break up through the pharynx and oral cavity. Spectral analysis and proper orthogonal decomposition are employed to quantify the dominant coherent structures. It is demonstrated that the intricacies of geometry create high vorticity zones and coherent structures.