Vorticity transport in human airway model

Andras Nemes, Sahar Jalal, Tristan Van De Moortele, Filippo Coletti

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Many previous studies concerned with respiratory fluid mechanics have simplistically assumed steady and laminar flow. Above a certain ventilation frequency, the unsteady nature of the respiratory flow becomes apparent, and inhalation and exhalation cannot be approximated as quasi-stationary processes. Moreover, due to the geometrical structure of the bronchial tree, flow unsteadiness and transition to turbulence can incept even at Reynolds numbers usually considered laminar in parallel flows. Here we investigate the primary features of the oscillatory flow through a 3D printed double bifurcation model that reproduces, in an idealized manner, the self-similar branching of the human bronchial tree. We consider Reynolds and Womersley numbers relevant to physiological conditions between the trachea and the lobar bronchi. Three-component, three-dimensional velocity fields are acquired at multiple phases of the ventilation cycle using Magnetic Resonance Velocimetry (MRV). The phase-averaged volumetric data provide a detailed description of the flow topology, characterizing the main secondary flow structures and their spatio-temporal evolution. We also perform twodimensional by Particle Image Velocimetry (PIV) for the steady inhalation case at a Reynolds number Re = 2000. PIV is carried out by matching the refractive index of the 3D printing resin with a novel combination of anise oil and mineral oil. The instantaneous measurements reveal unsteadiness of the separating unsteady flow in the bifurcation, and the ensemble averages show a clear Reynolds stress pattern indicating that the flow is turbulent at the first bronchial bifurcation already at this relatively low Reynolds number.

Original languageEnglish (US)
Title of host publication10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
PublisherInternational Symposium on Turbulence and Shear Flow Phenomena, TSFP10
Volume1
ISBN (Electronic)9780000000002
StatePublished - Jan 1 2017
Event10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017 - Chicago, United States
Duration: Jul 6 2017Jul 9 2017

Other

Other10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
CountryUnited States
CityChicago
Period7/6/177/9/17

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