Case Studies in the Human Respiratory System

Abstract

The use of CFD in biomedical applications has emerged as a legitimate alternative to traditional cast models and human experimental methods. With recent devel-opments in computational hardware, biomedical imaging instruments and CFD techniques, new and exciting research possibilities for the human respiratory system have emerged—some of which were discussed in Chap. 1. In the preceding chap-ters important fundamental steps were described in relation to the development of computational models of the respiratory system. The morphology and physiological nature of the respiratory system outlined in Chap. 2 highlights the increased level of complexity that is involved in biomedical CFD applications. For example, small scales, surface irregularities, and high curvatures are all characteristic of the nasal cavity, larynx and upper lung airway. These issues bring to fore the need for con-vergence of multi-disciplines, involving biomedical imaging, reverse engineering in Computer-Aided-Design (CAD), and finally CFD. In Chap. 3 the needed steps for reconstructing the respiratory passage were discussed. In fact, these preparatory steps can be viewed as a prerequisite for construction of any complex geometry. From the reconstructed CAD model, CFD simulations can then be undertaken by first developing a computational mesh (Chap. 4), and then applying the appropriate physics to suit the problem at hand. For example, fluid flow problems, such as in-halation and humidification of the inhaled air, need to consider the fundamentals of fluid dynamics as described in Chap. 5, whereas the inclusion of inhaled particles for drug delivery or for harmful particles suspended in the atmosphere require addi-tional particle equations and models which were discussed in Chap. 6. The correctly defined problem is then ready to be solved computationally. The numerical schemes and algorithms found in Chap. 7 are the cornerstone of any CFD analysis. Funda-mental understanding of the conservation equations and numerical approximations is prerequisite for generating efficient solutions. Having laid the groundwork to establish a strong theoretical base, this chapter cul-minates in the foundational knowledge attained by applying the theories and putting them into practice through selected demonstrative applications. From a practical viewpoint, the selected detailed case studies in this chapter will provide the reader J. Tu et al., Computational Fluid and Particle Dynamics in the Human Respiratory System, 233 Biological and Medical Physics, Biomedical Engineering, DOI 10.1007/978-94-007-4488-2_8, © Springer Science+Business Media Dordrecht 2013 234 8 Case Studies in the Human Respiratory System 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.