Advanced Topics and Future Trends
Over the last three decades there has been considerable progress in computational modelling. However many issues still need to be resolved. Advances in computational resources and techniques will enable significant progress to be made in modelling realist
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Advanced Topics and Future Trends
9.1
Introduction
Over the last three decades there has been considerable progress in computational modelling. However many issues still need to be resolved. Advances in computational resources and techniques will enable significant progress to be made in modelling realistic physiological scenarios of the respiratory system. The materials presented in this book thus far serve as an introduction to some of the current trends and modeling achievements, and in this chapter we present the latest developments and address some of the important issues and challenges that are currently faced by many researchers.
9.2 Advanced Modelling 9.2.1
Moving/Deforming mesh
Moving meshes can provide dynamic modelling of physiological functions that are transient in nature. Take for example the changes in lung shape and volume that occur during inhalation and exhalation. When the muscles of the diaphragm move downwards during inhalation, the ribcage expands creating more room for the lungs to expand. The volume of the lung increases which decreases the pressure relative to the outside air. This pressure difference drives the movement of air for inhalation. We can model this physiological function by attaching a hollow space that depicts the lung volume to the primary bronchus (first generation) of the tracheobronchial airway tree. The lung mesh is allowed to move freely with time while the trachea and bronchi are fixed and not moving. The moving grid can be allowed to slide along the interface without deformation between the part of the grid that is attached to the static bronchi and the other parts of the lung that are changing in size. Other techniques include dynamic layering where automatic layers of cells may be added or removed as the mesh moves. Local refinements of the mesh can also be applied to regions where the cell size and quality degrade due to the boundary motion. The J. Tu et al., Computational Fluid and Particle Dynamics in the Human Respiratory System, Biological and Medical Physics, Biomedical Engineering, DOI 10.1007/978-94-007-4488-2_9, © Springer Science+Business Media Dordrecht 2013
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9 Advanced Topics and Future Trends
Fig. 9.1 Schematic of the lung expansion and contraction to simulate the breathing process
Fig. 9.2 a CFD schematic of the computational domain for the cabin (Poussou et al. 2010), b 3D view of the cabin geometry, c velocity vector and contaminant transport due to movement of a person along the aisle (Mazumdar and Chen 2007)
grids do not have to match at the interface (which we call non-conformal meshing); this allows flexibility in employing different kinds of meshes and/or achieving the desired fineness in the respective domains. Except for difficulties in ensuring exact conservation, there are essentially no limitations on the applicability of this approach (Fig. 9.1). As another example of a moving mesh, we present the work by Mazumdar and Chen (2007) which investigated the air and contaminant flows in an airline cabin induced by a moving bod
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