Biomedical Engineering Reference
In-Depth Information
with confidence in applying the techniques to a wide range of biomedical engineering
applications. The computational model of a human nasal cavity and the upper lung
airways developed and described in Chaps. 3 and 4 is used for the case studies herein.
Analyses of the results are shown to inform the reader how to translate the myriad
of contours, vectors, and line plots and what to look out for in case of any spurious
results. Just like a medical practitioner reading CT or MRI scans needs the ability
to look for abnormalities, the colourful CFD results need expertise for interpreting
and distinguishing their significant features. Therefore this chapter has the following
important aims:
•
apply the theoretical knowledge attained from previous chapters through worked
case studies,
•
demonstrate different setup procedures that reflect the needs of individual cases,
•
demonstrate how to convert raw data into presentable contour and vector maps,
and line plots, and
•
demonstrate how to analyse the results and what type of results should be expected
under different cases.
8.2
Modelling Inhalation and Heat Transfer in the Nasal Cavity
The human nasal cavity, which performs a variety of physiological functions, is
an important component of the respiratory system. Individual aspects of the nasal
cavity, such as the geometry and flow rate, collectively affect nasal function by
bringing inspired air into contact with mucous-coated walls, thereby humidifying and
warming the air before it enters the lungs. The inspired air is heated and humidified
within the short distance from the nostrils to the nasopharynx (Inthavong et al. 2009b;
Keck et al. 2000a). To better understand the physiology of the nose, detailed airflow
patterns between the left and right nasal cavities can provide data that are pertinent
to the prediction of gas-particle flows and regional tissue exposure to inhaled air.
Because of the inter-subject variations inherent between nasal cavity geometries,
the numerical results herein are compared with experimental data available in the
literature to complement and reinforce the current knowledge base.
The fundamental physics and the CFD setup details that are needed in order to
study the effects of morphological differences in the left and right nasal cavities on the
airflow and heat transfer of inhaled air are discussed. The differences in the left and
right cavities will be explored and the effects they have on the flow field, especially in
the nasal valve and middle turbinate regions, are discussed. Geometrical differences
are also compared with available data in the literature. Additionally, variations in
the flow patterns and flow features such as pressure drop, wall shear stress, velocity,
and flow distribution between the left and right cavity as well as different geometries
are also presented. The flow in the nasal valve and turbinate region is studied in
particular detail to provide better insight into flows in this region.
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