Two-dimensional nonlinear Brinkman and steady-state Navier–Stokes equations for fluid flow in PCL

To remove mucus from the human body, periciliary layer (PCL) is an important region found in the human respiratory system. When a human inhales strange particles along with air into the body, goblet cells inside the epithelial cells secrete mucus to catch those particles and form a mucus layer on the top of the PCL. Since the velocity of the fluid in the PCL and cilia residing in the PCL affect the movement of mucus, in this work, we apply two-dimensional nonlinear Brinkman and steady-state Navier–Stokes equations to find the velocity of the fluid in the PCL. In the equations, the velocity of cilia is also contributed in the mathematical model which perturbs the fluid movement instead of the pressure gradient. Because bundles of cilia are considered in this work rather than a single cilium, the governing equations are derived from the hybrid mixture theory (HMT) which are the equations in a macroscopic scale. The numerical solutions are obtained by using a mixed finite element method of Taylor–Hood type and Newton’s method. We focus on five different angles of cilia that make with the horizontal plane. The velocity of the PCL fluid is presented for each angle. The numerical solutions obtained in this study can be useful in finding the mucus velocity that can help physicians to treat patients who have massive mucus in their lungs.