Visualization of flow resistance in physiological nasal respiration: analysis of velocity and vorticities using numerical simulation.

OBJECTIVES To visualize the velocity gradients and the vorticities of physiological unsteady nasal flow using the computational fluid dynamics method and to compare the inspiratory phase and expiratory phase flow patterns. DESIGN An anatomically correct 3-dimensional nasal and pharyngeal cavity was constructed from computed tomographic images of a healthy adult nose and pharynx. The unsteady state Navier-Stokes and continuity equations were solved numerically on inspiratory and expiratory nasal flow. SETTING Numerical simulation application. PARTICIPANTS Coronary and axial computed tomographic images from a healthy adult were used. MAIN OUTCOME MEASURES The detailed velocity distribution and vorticity (resistance) distribution of nasal airflow were visualized using the computational fluid dynamics method (an imaging technology for regional flow factors [velocity, vector, streamline, and vortex]). RESULTS In the inspiratory phase, a high-velocity area was prominent in the middle meatus, and the highest vorticity area had good agreement with this region. In the expiratory phase, the distributions of velocity and vorticities were flatter than those in the inspiratory phase. CONCLUSION The computational fluid dynamics model allows the investigation of airflow elements under physiological conditions, as well as the examination of the effect of nasal structure.