Fluid-structure interaction analysis of airflow in pulmonary alveoli during normal breathing in healthy humans

Abstract

In this work, the human lung alveoli are idealized by a three dimensional honeycomb like geometry and a fluid-structure analysis is performed to study the normal breathing mechanics. In contrast to previous works in which the inlet flow rate is predefined, in this model, we have applied a negative pressure on the outside surface of the alveolus which causes air to flow in and out of the alveolus. The integration of the experimental curve of breathing flow rate was used to approximate the shape of the external applied pressure. Our Fluid-Structure Interaction (FSI) model has an advantage over other literature since it addresses both the fluid dynamics and solid mechanics, simultaneously. The flow patterns confirmed that there is no circulation in the terminal alveolus. We have applied three distinct material models - linear isotropic elastic, hyperelastic, and viscoelastic - in order to simulate the mechanical behavior of alveolar wall tissue using ADINA software. The hysteresis behavior of the alveolar tissue was well predicted by a compliance diagram of the viscoelastic model while this behavior is not observed in the linear elastic and hyperelastic model. The stress and strain distribution is also obtained and is found to be non-uniform.