In our environment, chronic pulmonary illness due to pollution effects or asthmatic problems are increasing. To identify the contribution of pollution effect on the alterations in breath patterns, a better understanding of the human pulmonary system is needed. As a result, fields to be investigated are mostly flows in the lungs at high breathing frequency and aerosol deposition in lung bifurcations under unsteady conditions. The respiration pattern has to be better understood and investigated, to have the possibility to get the most appropriate palliative treatment. Most of the medical treatments are based on aerosol deposition in the bronchial tree.

The lung is a complex network of 23 successive generations of bifurcation (Weibel, 1963). The airways, from the trachea to the alveolar zone, divide by dichotomy and become shorter and narrower as they penetrate deeper into the lung. As a result, in vivo investigations of pulmonary flows are not possible, and in vitro experiments in models have to be performed.

Flows in the bifurcating airways of the lung are modeled to determine velocities and pressure fields. A complete description of steady flow in a single 3D bifurcation has been previously performed by experimental and numerical modeling. As a result of this study, it has been shown that the first bifurcation influences the flow in the second and in the third bifurcation when the length of the second bifurcation is not sufficiently long. To extend the investigations to a system of three generations, an experimental study of steady and unsteady flows has been carried out on a 2D multiple bifurcations model.

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