Visualizing flow partitioning in a model of the upper human lung airways

The convective transport of fluid within the human upper airways is investigated in a transparent model of the tracheobronchial tree. Oscillatory flow through the branching network with six generations was studied at varying Reynolds numbers between 400 and 2600 and Womersley numbers from 5.5 to 12.3 in the trachea representing clinical conditions during high frequency oscillatory ventilation. The flow partitioning within the model was visualized using advection of neutrally buoyant tracer particles, which were illuminated by short light pulses and recorded by a high speed camera. Integration of the particle locations for a large number of cycles provides the probability distribution of particles passing certain branches within the bifurcating network, and thus, the dispersion of particles in the airways. The results show the different characteristics of flow partitioning at varying Womersley and Reynolds numbers. [DOI: 10.1115/1.4000871] Keywords: respiratory flow, high frequency oscillatory ventilation (HFOV), in vitro model, flow partitioning, lung airways, mass transport