Ellipsoidal particle transport and deposition in an averaged human nasal airway — A CFD study

Airborne particles represent one of the major health challenges of our time, with micron-sized non-spherical particles, particularly fibrous ones, being of particular concern due to their ability to penetrate deep into the lungs and potentially cause disease. Despite their relevance, quantitative studies on the transport and deposition of non-spherical particles in realistic human nasal cavities remain sparse. Anatomical variability further complicates this problem, yet the limited availability of nasal cavity geometries restricts systematic investigation. To address this, we employ an averaged nasal cavity geometry, derived from multiple realistic replicas, to assess the influence of breathing scenarios on non-spherical particle transport and deposition. Fluid and particle simulations were conducted using an in-house OpenFOAM (V11) module in an Euler–Lagrangian framework, with steady RANS-based flow fields resolved using the k – ω SST turbulence model. Breathing conditions corresponding to rest and moderate exercise (7.5, 15, and 30 L/min ) were studied for particles with d eq = 2 . 5 – 20 μ m, considering both spherical and prolate ellipsoidal particles of different aspect ratios. Our results demonstrate that flow rate as well as both particle size and shape strongly influence deposition efficiency and local deposition patterns. Higher flow rates strongly amplify deposition hotspots while altering their distribution. Importantly, we show that simplified shape-factor models systematically overpredict deposition efficiencies for strongly elongated particles and misrepresent local deposition patterns compared to the Euler–Lagrange Euler-Rotation (EL-ER) approach. Note that mispredicted spatial deposition could lead to underestimating particle exposure to sensitive lung regions, misjudging drug delivery efficiency, or overlooking health risks from fibrous or elongated particles, highlighting the importance of an accurate representation of non-spherical, i.e. ellipsoidal, particle dynamics.