Airflow through the nasal cavity exhibits a wide variety of fluid dynamic behaviors due to the intricacy of the nasal geometry. The flow is naturally unsteady and perhaps turbulent, despite Computational Fluid Dynamics (CFD) in the literature being assumed as having a steady laminar flow. Time-dependent simulations can be used to generate detailed data with the potential to uncover new flow behavior, although they are more computationally intensive than steady-state simulations. Furthermore, verification of CFD results has relied on a reported pressure drop (e.g., nasal resistance) across the nasal airway although the geometries used are different. This study investigated the unsteady nature of inhalation at flow rates of 10 l/min, 15 l/min, 20 l/min, and 30 l/min. A scale resolving CFD simulation using a hybrid Reynolds-averaged Navier–Stokes--large eddy simulation model was used and compared with experimental measurements of the pressure distribution and the overall pressure drop in the nasal cavity. The experimental results indicated a large pressure drop across the nasal valve and across the nasopharynx, with the latter attributed to a narrow cross-sectional area. At a flowrate of 30 l/min, the CFD simulations showed that the anterior half of the nasal cavity displayed dominantly laminar but disturbed flow behavior in the form of velocity fluctuations. The posterior half of the nasal cavity displayed turbulent activity, characterized by erratic fluctuating velocities, which was enhanced by the wider cross-sectional areas in the coronal plane. At 15 l/min, the flow field was laminar dominant with very little disturbance, confirming a steady-state laminar flow assumption is viable at this flow rate.

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The primary objective of this research was to extract the essential information needed for setting atomization break up models, specifically, the Linear Instability Sheet Atomization (LISA) breakup model, and alternative hollow cone models. A secondary objective was to gain visualization and insight into the atomization break up mechanism caused by the effects of viscosity and surface tension on primary break-up, sheet disintegration, ligament and droplet formation. High speed imaging was used to capture the near-nozzle characteristics for water and drug formulations. This demonstrated more rapid atomization for lower viscosities. Image processing was used to analyze the near-nozzle spray characteristics during the primary break-up of the liquid sheet into ligament formation. Edges of the liquid sheet, spray break-up length, break-up radius, cone angle and dispersion angle were obtained. Spray characteristics pertinent for primary breakup modelling were determined from high speed imaging of multiple spray actuations. The results have established input data for computational modelling involving parametrical analysis of nasal drug delivery.

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For various sinonasal conditions, including chronic rhinosinusitis, saline irrigation is an accepted standard-of-care treatment. This study was aimed at determining the effect of increased irrigation volumes and greater squeeze force on mucosal irrigation. A sinonasal cavity computational model was reconstructed from high-resolution CT scans of a healthy, unoperated 25-year old female.Seven combinations of irrigation volumes (70, 150, 200, and 400 mL) and squeeze forces (ramp time 0.1, 0.5, and 1.0 s) at a fixed head tilt of 0 degrees to the horizontal (Frankfort position) were performed. Velocity, pressure, and wall shear stress, together with mapping of surface coverage and residual volumes at specific locations and time were demonstrated. Higher volume irrigation (400 mL) and greater squeeze force (ramp time 0.1 s) improved irrigation coverage on the ipsilateral and contralateral sinonasal surfaces and increased shear force (approximately 140 Pa). An increase in irrigation volume from 70 to 150 mL approximately doubled sinus surface coverage and from 70 to 200 mL tripled sinus surface coverage. A faster squeeze also contributed to increased sinus surface coverage but its effect was less influential. We infer that the greater irrigation volume and squeeze force improve therapeutic benefit in terms of lavage and distribution of topical medications.