Modeling Deposition In A Single Bifurcation Of The Respiratory Tract.
P.G. Kevrekidis, P.G. Georgopoulos (EOHSI, UMDNJ - R.W. Johnson Medical School and Rutgers University)
In this work, we present a simplified (two-dimensional) but self-consistent modeling approach to particulate matter dynamics in a single tracheobronchial bifurcation human airways. The principal aim of this methodology (that can be generalized to 3 dimensions in a straightforward manner) is to incorporate all the relevant physical processes and demonstrate their relative importance but also to indicate some significant weaknesses in previous formulations of the problem.
The model consists of a prescribed laminar flow and the tracer following of particles in a Lagrangian type of Molecular Dynamics approach, wherein Newton's equations of motion are solved for the particles. The effects of the most studied mechanisms of inertial impaction, gravitational sedimentation and diffusional deposition are incorporated but so are self-consistent expressions for the forces causing electrostatic precipitation. Also the generalization for the incorporation of hygroscopic growth within this framework is mathematically developed and the effect of generally believed to be less important mechanisms, such as diffusional charging and effective diffusivities due to axial mixing, is quantitatively examined.
The computer code is developed in a modular way using binary coefficients to flag on/off individual processes thus assessing the relative effect of the various mechanisms. Furthermore, all input coefficients can be straightforwardly modified to study different generations, different flow conditions or different particle characteristics. The results of the modular variation of processes and of particle and flow characteristics are reported and a number of striking results are found such as, for instance, the discrepancy between the model results and previous studies of the mechanisms inducing electrostatic precipitation. These results are discussed and explained in the light of the derived analytical expressions.
This work is a module component of the MENTOR framework (Modeling Environment for TOtal Risk studies) currently being developed at EOHSI.