Expiration flow in a symmetric bifurcation

This work investigates the fundamental flow in a converging bifurcation. Particle image velocimetry (PIV) and laser-induced fluorescence (LIF) experiments were conducted in a transparent model composed of three machined tubes mated together in a Y-shape. Measurements were taken in a plane containing the axes of the tubes and in the cross-sectional plane of the parent tube to elucidate flow patterns in the bifurcating passages of the human respiratory system. The primary objective was to determine the amount of secondary flow in a bifurcation during expiration. PIV measurements in the transverse plane show detailed characteristics of the secondary flow. Results at higher Re illustrate unsteadiness associated with a hairpin vortex and symmetry-breaking. This study addresses the transport of particles of small Stokes number that survive inertial impaction during inhalation and remain in suspension over multiple breathing cycles. Knowledge of the underlying airflow is required to develop an accurate dosimetry model to transport prescription drugs with precision into the bloodstream. Similarly, the harmful impact of pollutants on the respiratory system can only be assessed by first understanding the carrier airflow.