Numeric investigation of non-stationary dust-containing airflow and deposition of dust particles in the lower airways

Within creation of the mathematical model to describe the human respiratory system, we accomplished numeric investigation of non-stationary dust-containing airflow as well as dust particle deposition in the lower airways with the real anatomic geometry based on CT scans. Inhaled air is considered a multi-phase mixture of a homogenous gas and solid dust particles. Motion of a basic carrier gas phase is described using the Euler approach. Solid dust particles are a dispersed carried phase, which is described with the Lagrange approach. The $k$–$\omega$ model is used to describe turbulence. We consider non-stationary airflow during calm inhalation. The article presents calculated flow streamlines for the velocity of particles in inhaled air in the lower airways at different moments. We quantified a share of deposited particles (SDP) with various dispersed structure (between 10 nm and 100 $\mu$m) and density (1000 kg/m$^3$, 2000 kg/m$^3$, 2700 kg/m$^3$) in the lower airways; the article provides computed motion paths of particulate matter. Solid particle deposition in the airways has different efficiency depending on particle sizes and density. SDP goes down as their sizes and masses decrease. Particle density mostly influences differences in deposition of micro-sized particles (2.5–20 $\mu$m): as particle mass and density grow, SDP in the airways also increases. SDP with their diameter being less than 1$\mu$m amounts to approximately 20% of all the particles that reach the inlet to the trachea. According to the results obtained by numeric modeling, the greatest share of dust particles penetrates the right main bronchus, predominantly the right middle and inferior lobar bronchi. Dust particles are able to induce diseases of the lungs, pneumoconiosis included.