Validation of computational fluid dynamics methodology used for human upper airway flow simulations.
An anatomically accurate human upper airway model was constructed from multiple magnetic resonance imaging axial scans. This model was used to conduct detailed Computational Fluid Dynamics (CFD) simulations during expiration, to investigate the fluid flow in the airway regions where obstruction could occur. An identical physical model of the same airway was built using stereo lithography. Pressure and velocity measurements were conducted in the physical model. Both simulations and experiments were performed at a peak expiratory flow rate of 200 L/min. Several different numerical approaches within the FLUENT commercial software framework were used in the simulations; unsteady Large Eddy Simulation (LES), steady Reynolds-Averaged Navier-Stokes (RANS) with two-equation turbulence models (i.e. k-epsilon, standard k-omega, and k-omega Shear Stress Transport (SST)) and with one-equation Spalart-Allmaras model. The CFD predictions of the average wall static pressures at different locations along the airway wall were favorably compared with the experimental data. Among all the approaches, standard k-omega turbulence model resulted in the best agreement with the static pressure measurements, with an average error of approximately 20% over all ports. The highest positive pressures were observed in the retroglossal regions below the epiglottis, while the lowest negative pressures were recorded in the retropalatal region. The latter is a result of the airflow acceleration in the narrow retropalatal region. The largest pressure drop was observed at the tip of the soft palate. This location has the smallest cross section of the airway. The good agreement between the computations and the experimental results suggest that CFD simulations can be used to accurately compute aerodynamic flow characteristics of the upper airway.
Mylavarapu
Goutham
G
Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati,United States.
Murugappan
Shanmugam
S
Department of Otolaryngology-Head and Neck Surgery, University of Cincinnati,Medical Center, United States.
Mihaescu
Mihai
M
Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati,United States.
Kalra
Maninder
M
Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039 , United States. Electronic address: maninderkalra@gmail.com.
Khosla
Sid
S
Department of Otolaryngology-Head and Neck Surgery, University of Cincinnati,Medical Center, United States.
Gutmark
Ephraim
E
Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati,United States; Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229-3039 , United States.
D000293:Adolescent; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D045853:Exhalation / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008954:Models, Biological; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D012984:Software