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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.

Aim:  To develop a novel laboratory procedure for the study of shock wave‐induced damage to Bacillus endospores. Methods and Results:  Bacillus atrophaeus endospores are nebulized into an aerosol, loaded into the stanford aerosol shock tube and subjected to shock waves of controlled strength. Endospores experience uniform test temperatures between 500 and 1000 K and pressures ranging from 2 to 7 atm, for a relatively short time (2–3 ms). During this process, the bioaerosol is observed using in situ laser absorption and scattering diagnostics. Additionally, shock‐treated samples are extracted for ex situ analysis including viability plating, flow cytometry and SEM imaging. Measurements indicate that endospores lose the ability to form colonies when heated to test temperatures above 500 K while significant breakdown in morphology is observed at test temperatures above 750 K. Conclusion:  These results demonstrate the disruption of essential biochemical pathways or biomolecules prior to the onset of significant endospore morphological deterioration. Significance and Impact of the Study:  This novel laboratory approach to study the interaction of endospores with shock waves provides an experimental means to investigate the mechanisms of endospore resistance to rapid heating. In addition, this methodology allows for the direct simulation of a blast wave–bioaerosol interaction in an atmospheric environment.