Solving for unsteady airflow in a glottal model with immersed moving boundaries

This work builds on previous efforts to characterize the dynamic development of the airflow in the glottis from a fluid mechanical point of view. A multigrid finite-difference method with immersed boundaries is implemented to solve the Navier–Stokes equations in a channel constricted by a vibrating rigid structure with a shape conforming to the human vocal folds. For the dynamically evolving boundaries we apply a forced oscillation glottal model. The large scale deformations of the boundaries are handled without regridding and tracheal input velocity is either set to a constant value or synchronized with wall motion. Particular attention is paid to the mobility of the point where the airflow detaches from the flapping walls. Results illustrate the relevance and the diversity of flow separation dynamics within the constriction standing for the glottis, while flow instabilities past the constriction are not found to affect flow behavior between the moving walls significantly. A comparison between static and dynamic numerical experiments show that mobility of the flow separation point is nontrivial in general and only rarely quasi-static.