Fully turbulent flow in a physiologically realistic human airway bifurcation

Abstract

Recent computational studies have shown that the airflow in the upper human airways is turbulent during much of the respiratory cycle. A feature of respiratory airflow that poses a challenge to computations based on Reynolds-Averaged Navier-Stokes (RANS) closures is the laminarturbulent-laminar transition as the flow moves from the mouth through the glottis and down to the lower conducting airways. Turbulence and unsteadiness are expected at least through the first few bifurcations of the airways. In the case of inhaled medicines, and depending on the size of the particles in the formulation, airway bifurcations are areas of preferential deposition. In this study we perform for the first time, Large Eddy Simulations (LES) and Direct Numerical Simulations (DNS) of fully developed turbulent flow through a single human airway bifurcation, emulating steady prolonged inspiration and expiration conditions. We also perform RANS simulations via the v2 - f closure model and compare with our DNS and LES results. We examine the mean flow characteristics and the turbulent vortical structures as well as their effect on the deposition of particles of different sizes.