Eulerian modelling of lung deposition with sectional representation of aerosol dynamics

A dynamical model of respiratory deposition is developed based on an Eulerian approach. The model simulates detailed lung deposition along all generations of the respiratory tract by solving numerically the aerosol general dynamics equation (GDE). All deposition mechanisms are described mechanistically, without using any empirical correlations. The GDE is solved in a one-dimensional form using a sectional method to describe the aerosol size distribution. To describe lung geometry the classical Weibel's morphometric model is used, employing a time-varying alveolar geometry to accommodate inhalation dynamics. A computationally efficient methodology is implemented based on a time-step splitting and subcycling approach, combined with a moving grid method for the growth process. The model is validated by comparing extensively with experimental and numerical results. The simulation results show that aerosol dynamics, in particular condensational growth, significantly influence respiratory deposition of fine hygroscopic particles. Instead, the effect of coagulation was found to be negligible. Particle deposition in terms of number, surface, or mass is addressed, which is of interest to current inhalation toxicology studies.