title: Particle deposition in a realistic geometry of the human conducting airways: Effects of inlet velocity profile, inhalation flowrate and electrostatic charge.
abstract: Understanding the multitude of factors that control pulmonary deposition is important in assessing the therapeutic or toxic effects of inhaled particles. The use of increasingly sophisticated in silico models has improved our overall understanding, but model realism remains elusive. In this work, we use Large Eddy Simulations (LES) to investigate the deposition of inhaled aerosol particles with diameters of dp=0.1,0.5,1,2.5,5 and 10μm (particle density of 1200kg/m(3)). We use a reconstructed geometry of the human airways obtained via computed tomography and assess the effects of inlet flow conditions, particle size, electrostatic charge, and flowrate. While most computer simulations assume a uniform velocity at the mouth inlet, we found that using a more realistic inlet profile based on Laser Doppler Anemometry measurements resulted in enhanced deposition, mostly on the tongue. Nevertheless, flow field differences due to the inlet conditions are largely smoothed out just a short distance downstream of the mouth inlet as a result of the complex geometry. Increasing the inhalation flowrate from sedentary to activity conditions left the mean flowfield structures largely unaffected. Nevertheless, at the higher flowrates turbulent intensities persisted further downstream in the main bronchi. For dp>2.5μm, the overall Deposition Fractions (DF) increased with flowrate due to greater inertial impaction in the oropharynx. Below dp=1.0μm, the DF was largely independent of particle size; it also increased with flowrate, but remained significantly lower. Electrostatic charge increased the overall DF of smaller particles by as much as sevenfold, with most of the increase located in the mouth-throat. Moreover, significant enhancement in deposition was found in the left and right lung sub-regions of our reconstructed geometry. Although there was a relatively small impact of inhalation flowrate on the deposition of charged particles for sizes dp<2.5μm, impaction prevailed over electrostatic deposition for larger particles as the flowrate was increased. Overall, we report a significant interplay between particle size, electrostatic charge, and flowrate. Our results suggest that in silico models should be customized for specific applications, ensuring all relevant physical effects are accounted for in a self-consistent fashion.
authors.affiliation: Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Kallipoleos Avenue 75, Nicosia 1678, Cyprus.
authors.forename: P G
authors.initials: PG
authors.lastname: Koullapis
authors.affiliation: Computational Sciences Laboratory (UCY-CompSci), Department of Mechanical and Manufacturing Engineering, University of Cyprus, Kallipoleos Avenue 75, Nicosia 1678, Cyprus. Electronic address: kassinos@ucy.ac.cy.
authors.forename: S C
authors.initials: SC
authors.lastname: Kassinos
authors.affiliation: International Centre for Indoor Environment and Energy, Technical University of Denmark, Building 402, 2800 Lyngby, Denmark.
authors.forename: M P
authors.initials: MP
authors.lastname: Bivolarova
authors.affiliation: International Centre for Indoor Environment and Energy, Technical University of Denmark, Building 402, 2800 Lyngby, Denmark.
authors.forename: A K
authors.initials: AK
authors.lastname: Melikov
mesh_terms: D003198:Computer Simulation; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000033:anatomy & histology* / Q000502:physiology*; D008954:Models, Biological; D010316:Particle Size; D055672:Static Electricity
keywords: Aerosol deposition in the human upper airways; Computational fluid-particle dynamics simulation; Electrostatic image charge force; Inlet conditions; Large eddy simulation; Steady inhalation