STUDY OF THE DYNAMICS OF RESPIRATORY EVENTS IN PATHOGEN-LADEN EXHALATIONS AND SOLID PARTICLE INHALATIONS
This doctoral thesis investigates the dynamics of violent expiratory events (coughing and sneezing) and the inhalation of particles in the upper respiratory system using experimental and numerical approaches. The COVID-19 pandemic highlighted the limitations of previous studies, including high inter-subject variability and geometric simplifications in computational models. To overcome these shortcomings, a device was developed that can reproduce intense expiratory events within physiological ranges, incorporating a realistic 3D-printed geometry of the upper respiratory tract, including the nasal cavity. Experimental results indicate that the presence of the nasal cavity modifies aerosol dispersion, reducing the horizontal distance traveled while increasing vertical spread. In the absence of the nasal cavity, secondary vortices are generated, which could increase the risk of transmission. Numerical studies validated with the experimental results were also conducted. The effect of physiological temperature under controlled environmental conditions was evaluated, demonstrating that greater temperature differences between exhaled air and the ambient environment increase buoyancy, horizontal displacement, and the concentration of suspended microdroplets, leading to the development of a mathematical expression capable of accurately predicting aerosol reach. Additionally, a numerical study of particle inhalation within the nasal cavity was carried out using an innovative particle-interaction model. Small (< 10 μm) and elongated particles tend to bypass nasal filtering and reach the lower respiratory system, while larger particles (> 10 μm) deposit primarily in the nasal cavity. The results of this research provide insights into aerosol transport and particle deposition, offering a basis for optimizing ventilation and air filtration systems, as well as mitigation strategies for pathogen transmission in critical indoor environments.
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