COMPUTATIONAL FLUID DYNAMICS SIMULATION OF THE AIRFLOW THROUGH THE HUMAN RESPIRATORY TRACT By Jamasp Azarnoosh Kidambi Sreenivas Abdollah Arabshahi Research Professor, Research Professor, Computational Engineering Computational Engineering (Chairperson/Principal Adviser) (Committee Member) James C. Newman, III Professor, Computational Engineering (Committee Member) 1 COMPUTATIONAL FLUID DYNAMICS SIMULATION OF THE AIRFLOW THROUGH THE HUMAN RESPIRATORY TRACT By Jamasp Azarnoosh A Thesis Submitted to the Faculty of the University of Tennessee at Chattanooga in Partial Fulfillment of the Requirements of the Degree of Master of Science: Engineering The University of Tennessee at Chattanooga Chattanooga, Tennessee August 2016 ii ABSTRACT This study compares the effect of extra-thoracic airways (ETA) on the flow field through the lower airways by carrying out simulations of the airflow through the human respiratory tract. Three geometries, consisting of the ETA, CT-derived lower airway, and a combination of the two were utilized in simulations that were performed for transient breathing in addition to constant inspiration/expiration. Physiologically-appropriate regional ventilation for two different flow rates was induced at the distal boundaries by imposing appropriate lobar specific flow rates. Two breathing rates were considered, i.e., 7.5 and 15 breaths per minute with a tidal volume of 0.5 liter. For comparison, the flow rates for constant inspiration/expiration were selected to be identical to the peak flow rates during the transient breathing. Significant differences indicate that simulations that utilize constant inspiration or expiration may not be appropriate for gaining insight into the flow patterns through the human airways. iii ACKNOWLEDGEMENTS First and foremost, I truly appreciate my major advisor, Dr. Kidambi Sreenivas for his advice, guidance throughout this research. I would like to thank my committee members, Dr. Abi Arabshahi and Dr. James Newman III, for valuable discussions and their helps. Furthermore, I really thank Richard R. Gruetzemacher, III for sharing his vast knowledge in this research. Indeed, this thesis would not have been possible without the support and assistance of him. iv TABLE OF CONENTS ABSTRACT ................................................................................................................................... iii ACKNOWLEDGEMENTS ........................................................................................................... iv LIST OF TABLES ........................................................................................................................ vii LIST OF FIGURES ....................................................................................................................... ix LIST OF ABBREVIATIONS ...................................................................................................... xiv LIST OF SYMBOLS .................................................................................................................... xv CHAPTER I. INTRODUCTION ................................................................................................................. 1 II. LITERATURE REVIEW ..................................................................................................... 3 III. COMPUTATIONAL METHODS ....................................................................................... 8 3.1. Computational Geometries .......................................................................................... 8 3.1.1. The Idealized Upper Airway Geometry (Alberta Geometry) ............................. 8 3.1.2. The Lower Airway Geometry (CT-based Airway)............................................ 10 3.1.3. The Entire Airway Geometry .............................................................................11 3.2. Mesh Generation ........................................................................................................ 12 3.3. Flow Solver ................................................................................................................ 13 3.4. Numerical Solution .................................................................................................... 15 3.5. Boundary Conditions ................................................................................................. 17 IV. RESULTS AND DISCUSSION ........................................................................................ 19 v 4.1. The Idealized Upper Airway Geometry (the ETA geometry) .................................... 19 4.1.1. Validation with Experimental Data and Computation Simulations .................. 20 4.1.1.1. Cross-Section 1 ........................................................................................ 23 4.1.1.2. Cross-Section 2 ........................................................................................ 24 4.1.1.3. Cross-Section 3 ........................................................................................ 27 4.1.1.4. Cross-Section 4 ........................................................................................ 29 4.1.1.5. Cross-Section 5 ........................................................................................ 31 4.1.1.6. Cross-Section 6 ........................................................................................ 35 4.1.1.7. Cross-Section 7 ........................................................................................ 37 4.1.1.8. Outflow .................................................................................................... 39 4.1.2. Transient Breathing Cycle and Constant Inspiration/Expiration ...................... 45 4.1.2.1. Inspiration ................................................................................................ 45 4.1.2.2. Expiration ................................................................................................. 51 4.2. The Lower Airway Geometry .................................................................................... 56 4.2.1. Inspiration ......................................................................................................... 57 4.2.2. Expiration .......................................................................................................... 61 4.3. The Entire Airway Geometry ..................................................................................... 64 4.3.1. Inspiration ......................................................................................................... 64 4.3.2. Expiration .......................................................................................................... 69 4.4. Comparison of the Entire Airway with the ETA and the Lower Airway only ........... 71 4.4.1. Inspiration ......................................................................................................... 72 4.4.2. Expiration .......................................................................................................... 81 V. CONCLUSION .................................................................................................................. 90 VI. FUTURE WORK .............................................................................................................. 93 REFERENCES ............................................................................................................................. 94 VITA ............................................................................................................................................. 98 vi LIST OF TABLES 3.2.1 Number of nodes and volume elements of all grids ...................................................... 13 3.4.1 Parameters for the breathing cycles considered in this study ........................................ 16 3.5.1 Lobar volumes in the lung ............................................................................................. 17 4.1.1 Comparison of the local Reynolds number and local bulk velocity (Ulocal) between PIV data, the LBM and LES solutions at the inlet and seven cross-sections ..................................................................................................... 41 4.1.2 Reynolds numbers of constant and transient breathing cycle during inspiration at all seven traverse cross-sections of the ETA ...................................................... 51 4.1.3 Reynolds numbers of constant and transient breathing cycle during expiration at all seven traverse cross-sections of the ETA ...................................................... 56 4.4.1 Reynolds number of constant and transient breathing cycle during inspiration at all five lobar bronchi in the lower airway only .................................................. 79 4.4.2 Values of TKE, U and TI during inspiration at all five lobar bronchi in the lower airway only......................................................................................................... 79 4.4.3 Reynolds number of constant and transient breathing cycle during inspiration at all five lobar bronchi in the entire airway .......................................................... 80 4.4.4 Values of TKE, U and TI during inspiration at all five lobar bronchi in the entire airway ................................................................................................................. 81 4.4.5 Reynolds number of constant and transient breathing cycle during expiration at all five lobar bronchi in the lower airway only ......................................................