Experimental Investigation of Aerosol Deposition in Alveolar Lung Airways

Abstract Studies related to aerosol deposition in the alveolar pulmonary airways have been mostly restricted to numerical studies, which require further experimental validation. Few experimental studies have been performed extracting quantitative data due to the involved complexity accompanying the extremely low Reynolds-numbers (in the order of 0.01) encountered in the lower lung airways. This article presents measurements of both fluid velocity and aerosol trajectories conducted in a curved pipe with cylindrical cavities representing the alveolar structures in the 21st generation in the Weibel model. These could later be used in the validation of numerical codes. It turned out to be impossible to model simultaneously Reynolds, gravitational and inertial similarity for the aerosol particles. As one of the main objectives was to act as a benchmark test for numerical codes rather than to accurately simulate the conditions encountered in the alveoli, iron particles of 1.2mm in diameter were chosen for, representing aerosols with in-vivo diameters of 12.8µm. Silicone oil served as carrier fluid allowing flow rates of 0.84ml/s corresponding to Reynolds numbers of 0.07. Using iron particles of 20µm as tracers, PIV experiments were conducted to extract the steady flow velocity distributions. After background subtraction the images were processed with an algorithm, which combines the advantages of multigrid window distortion during the iterative interrogation process and ensemble correlation. As such the negative influences of poor image quality and low seedin