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Modeling of Airflow Characteristics and Particle Deposition in Human Upper Respiratory Tract Using CFD Simulations
Pospíšil, Milan ; Forjan, Mathias (oponent) ; Paštěka, Richard (vedoucí práce)
The objectives are to analyze the mechanisms of airflow and particle transport in the extrathoracic airways. Understanding these features in greater detail not only helps in the treatment of diseases related to the respiratory tract but also aims to reduce the amount of animal testing. For the evaluation, computational fluid dynamic (CFD) simulations were utilized. ANSYS was used as a leading software to perform a simulation of different inspiratory flow rates. In this work, Large Eddy Simulations (LES) is engaged due to its real-world performance. The geometry of the upper airways is obtained from CT scans, to preserve the topological data of the upper airways. Furthermore, the deposition of inhaled particles of varying diameters 1-10 m was examined, helping us better understand the therapeutic effects of inhaled particles. Two types of inhalations simulations were carried out. First, inhalation through the nose, simulating the inhalation with a nebulizer with airflow rates of 15 l/min and 30 l/min. Second, through mouth simulating inhalation with a dry-powder inhaler with a flow rate of 90 l/min. Simulated results show that most of the particles deposit at the entrance of the nasal or oral cavity. When flow rates of 15 and 30 l/min were compared, it can be seen the higher initial velocity is, the particles of large diameter (6-10 m) are stuck in the nasal cavity and do not appear in the laryngeal region, whereas with low velocity the more particles of 6-10 m can be found in this region. The maximum number of particles leaving the trachea was observed with a flow rate of 15 l/min, accounting for 26 %. As opposed to 90 l/min where only 13 % left the upper respiratory tract. Also, typical pressure drop can be observed in pressure contours describing the larynx region. This was most significant for a flow rate of 90 l/min where the pressure from the oropharynx to subglottis dropped by 490 Pa.
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