Case Studies in the Human Respiratory System - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 239

to stimulate epithelium cellular mechanisms, thus contributing to the induction of
goblet cell secretion (Rogers 1994).
As shear stresses are linearly related to the local velocity, these values significantly
increase as breathing efforts increase. High shear stresses that are concentrated lo-
cally may cause irritation of the blood vessels within that area. The maximum shear
stresses that occur in the nasal valve region and to a lesser extent in the main nasal
passageway may lead to dysfunctional effects on nasal sensation of airflow and there-
fore play a role in the well-being of nasal breathing. By mapping out the distribution
of external stresses on the nasal cavity walls, predictions of the mechanoreceptor
response can be estimated.

8.2.5 Flow Visualisation

Path streamlines Path streamlines, which act as massless particle tracers to track the
flow path of the inhaled air, were released from the nostril inlet to provide qualitative
visualisation of the flow field. The streamlines in the left nasal cavity at a flow rate
of 7.5 L/min show flow separation and reversed flow just posterior to the narrowest
valve (Fig. 8.6 a). A prominent vortex in the upper anterior part of the cavity was
formed. This vortex is a result of the adverse pressure gradient caused by the abrupt

Fig. 8.6 Representation of flow streamlines in current nasal cavity. A comparison of streamlines
produced in the literature shows similar trends (see Fig. 8.7 ). a Left cavity , 7.5 L/min. b Right
cavity , 7.5 L/min. c Left cavity , 15L/min. d Right cavity , 15L/min