The effect of intrasubject variation on the turbulent
flow and aerosol deposition in the extrathoracic airways
is studied in two realistic mouth-throat geometries
from the same subject. An immersed boundary
method is applied which simplifies the task of grid
generation for the complex extrathoracic geometries
and allows the use of a structured grid solver. Curvilinear
grids that roughly follow the shape of the geometries
are adopted, allowing for much higher resolution
within the geometries than Cartesian grids commonly
used in IB methods. An added advantage is
that the grid lines are approximately aligned with the
streamlines, which reduces numerical diffusive errors.
The numerical simulations allow us to explain in vitro
aerosol deposition data in the literature for the same
mouth-throat models. The position of the tongue during
inhalation is shown to have a significant impact on
both the mean flow patterns and the turbulence intensities,
which in turn affects extrathoracic deposition.