Simulation of air motion in human lungs during breathing. Dynamics of liquid droplet precipitation in the case of medicine drug aerosols

The paper deals with numerical simulation of the air flow in the full human bronchial tree. In their previous studies, the authors developed an analytical model of the full human bronchial tree and a method of stage-by-stage computation of the respiratory tract. A possibility of using the proposed method for a wide range of problems of numerical simulations of the air flow in human lungs is analyzed. The following situations are considered: 1) steady inspiration (with different flow rates of air) for circular and “starry” cross sections of bronchi (“starry” cross sections models some lung pathology); 2) steady expiration; 3) unsteady inspiration; 4) precipitation of medical drug aerosol droplets in human bronchi. The results predicted by the proposed method are compared with results of other researchers and found to be in good agreement. In contrast to previous investigations, the air flow in the full (down to alveoli) bronchial tree is studied for the first time. It is shown that expiration requires a greater pressure difference (approximately by 30%) than inspiration. Numerical simulations of precipitation of medical drug aerosol droplets in the human respiratory tract show that aerosol droplets generated by a standard nebulizer do not reach the alveoli (the droplets settle down in the lower regions of the bronchi).