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Air Flow and Respiratory Gas Exchange Simulation in Acinar Region of Human Lung

Eslami Saray, Mohammad Ali | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44047 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Saeed
  7. Abstract:
  8. The main function of respiratory system is to exchange gasses between air and blood. However selection of the suitable geometry and solution of the fluid flow precede all other phenomena in the lung, including particle deposition and gas exchange. The most complicated phenomena take place at the terminal generations of the lung which is known as acinar region. Due to small dimensions and inability to use experimental measurements, numerical simulations are adequate methods in this region. In the first part of this thesis a method is proposed to reduce the computational space and make it possible to model all acinar region, simultaneously. Results show that the characteristic of streamlines in primary generations is the existence of recirculation region in alveoli, while terminal generations are characterized by radial flows which move towards the alveolar wall. The ratio of alveolar to ductal flow rate specifies the dominant flow patterns in each generation. Ratios below 0.007 correspond to the recirculatory flow pattern, while ratios above this threshold correspond to radial flow pattern. The other aim of this thesis is to study the gas exchange between air and blood. For this purpose, a novel 3D model of the acinar region and the capillary network around it is proposed and exchange of oxygen and carbon dioxide are simulated using unsteady scalar transport equations. Results show that during normal breathing, the partial pressure of oxygen in the air is always between 134 to 140 mmHg and the partial pressure of carbon dioxide is between 13 to 37 mmHg. The concentrations of these two gases in blood are respectively between 6.3 to 8.6 and 48.4 to 53.4 mol/m3. As the rate of ventilation increases, the partial pressure of oxygen is also increased and the partial pressure of carbon dioxide is decreased
  9. Keywords:
  10. Computational Fluid Dynamics (CFD) ; Dynamic Mesh ; Acinus ; Gas Exchange ; Alveolar Zone ; Capillary Network

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