CFD simulation of a CT scan oral-nasal extrathoracic model

Abstract

The study of air flow dynamics through the respiratory system is one of the leastresearched areas in the biofluid field. Computational fluid dynamics (CFD) has become an essential tool for analysing the airway flows due to the complex geometries involved. In this research a full process for obtaining the CFD simulation results from a CT scan has been developed. The complete extrathoracic oro-nasal airways, and the upper tracheobronchial region, have been studied in this research. The nasal route up to the trachea was obtained from CT images of a healthy woman, with the help of the free medical reconstruction software InVesalius. The oral cavity and lower airways were modelled from previous bibliographic geometry. The stereolithography file extracted from the scan was joined in a CAD program together with the other geometry and included the outer surface of a person and a far wall to simulate more realistic breathing conditions. The meshing process was performed with Gambit and Tgrid, and simulations were done with the Ansys solver Fluent. The velocity and pressure fields were calculated for the entire range of physiological capacity. The flow behaviour and respiratory effort under different breathing conditions were analysed. The volume airflow and pressure drop curves through oral and nasal routes were compared at difference activity levels. Interesting behaviours were found when comparing different breathing pattern results, and the importance of using a realistic geometry was demonstrated. This study has also provided the basis for the development of simulations starting from scanner data for future research. Some technical aspects in automated scan reconstruction still need to be resolved before this process become a standard tool for rhinology. © 2013 WIT Press.