Abstract
The flow characteristics in the realistic human upper airway (HUA) with obstruction that resulted from pharyngeal collapse were numerically investigated. The 3D anatomically accurate HUA model was reconstructed from CT-scan images of a Chinese male patient (38 years, BMI 25.7). The computational fluid dynamics (CFD) with the large eddy simulation (LES) method was applied to simulate the airflow dynamics within the HUA model in both inspiration and expiration processes. The laser Doppler anemometry (LDA) technique was simultaneously adopted to measure the airflow fields in the HUA model for the purpose of testifying the reliability of LES approach. In the simulations, the representative respiration intensities of 16.8 L/min (slight breathing), 30 L/min (moderate breathing), and 60 L/min (severe breathing) were conducted under continuous inspiration and expiration conditions. The airflow velocity field and static pressure field were obtained and discussed in detail. The results indicated the airflow experiences unsteady transitional/turbulent flow in the HUA model under low Reynolds number. The airflow fields cause occurrence of forceful injection phenomenon due to the narrowing of pharynx caused by the respiratory illness in inspiration and expiration. There also exist strong flow separation and back flow inside obstructed HUA owing to the vigorous jet flow effect in the pharynx. The present results would provide theoretical guidance for the treatment of obstructive respiratory disease.
Highlights
The inhaled particles are the culprit for aggravating fog and haze pollution, which seriously jeopardizes the human health
The human upper airway (HUA), which consists of oral cavity, nasal cavity, pharynx, larynx, and trachea, is the main passageway for inhaled particles damaging human health, resulting in respiratory diseases range from simple common cold, snoring, and obstructive sleep apnea (OSA) to more serious pneumonia and even lung cancer [1, 2]
The respiratory intensity in experiments and simulations was set to be constant with Q = 16.8 L/min, which corresponded to a constant inlet velocity of u = 0.8 m/s that was calculated according to the respiratory intensity and the nostril cross-sectional area
Summary
The inhaled particles are the culprit for aggravating fog and haze pollution, which seriously jeopardizes the human health. The human upper airway (HUA), which consists of oral cavity, nasal cavity, pharynx, larynx, and trachea, is the main passageway for inhaled particles damaging human health, resulting in respiratory diseases range from simple common cold, snoring, and obstructive sleep apnea (OSA) to more serious pneumonia and even lung cancer [1, 2]. Many experimental studies have been carried out to explore airflow properties in the laboratory HUA models. Girardin et al (1983) applied the LDA measurements to determine the velocity field in a human nasal cavity model made of cadaver at five coronal sections [3].
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