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Experimental Assessment of the Laryngeal Jet Effect on the Fluid Flow Pattern within the Trachea

Salehi, Mehran
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470386999

Abstract Details

2016, Doctor of Philosophy, University of Toledo, Mechanical Engineering.
Drug aerosol inhalation is a modern way to combat lung diseases. It is also becoming the preferred route for insulin delivery, pain management, cancer therapy and nanotherapetutics. The specific airflow characteristics within the central human airways, however, have a major influence on aerosol delivery and particle deposition. In this study the association of human inspiratory laryngeal function on the unique transitional turbulence this creates in the central airways and its association to particle deposition were investigated. The true vocal cords expand with increasing inspiratory flow rates and independently, with enlarging lung volumes. This creates a specific constriction to the inspiratory airstream and subsequent vortex formation below each vocal cord. The study compares triangular vocal cord shapes (physiologic) to rectangular (symmetric) shapes over a range of inspiratory directed flows. Disturbances below the laryngeal obstruction were visualized and the turbulence intensities as a function of distance below the vocal cord constriction in scale models under similitude flow conditions for a human trachea was also measured using laser Doppler anemometry in both primary (axial) and secondary (tangential) directions in a simplified larynx-trachea model. The turbulence length scale and energy spectrum were also calculated using hot-wire anemometer data to determine the size distribution of eddies and the rate of energy decay along the trachea for different larynx geometries and Reynolds numbers. Both visualizations and measurements were made at Reynolds numbers between 1000 and 4000 which represent mild to severe breathing conditions. The larynx geometry is modeled by a constriction inside a straight tube. The group of constrictions consists of 2 rectangular and triangular shapes at apex angles of 45º, 60º and 75º degrees. The base circular tube was 5 cm in diameter (D) and 30 cm in length (L) (to keep the relative ratio of L/D=6). The inlet area created by the larynx constriction is approximately 10% and 50% of the tube area. Forty eight different combinations of aperture, area ratio, angle of the glottis and flow rates were visualized. Arrays of 72 measurements were made respectively at downstream planes of 1D and 3D from the larynx within the trachea. Results show that both the average and rms velocities change rapidly with respect to distance down the trachea. High levels of turbulence intensity at the anterior part indicate the potential region for particle deposition. The two vortices below the laryngeal constriction appear to interact, creating a transitional turbulence which propagates down the trachea, developing a structure to the turbulence which enhances the lateral flow energies and in turn enhances particle movements toward the tracheal walls (especially the posterior membranous tracheal wall) and subsequent particle capture. It appears that the locations of particle capture on the tracheal walls are at sites optimal for subsequent expectoration with cough.
Terry Ng (Advisor)
Dan Olson (Committee Member)
Abdollah Afjeh (Committee Member)
Sorin Cioc (Committee Member)
Jeffrey Hammersely (Committee Member)
Ronald Scherer (Committee Member)
Fluid Dynamics; Mechanical Engineering

Recommended Citations

Citations

  • Salehi, M. (2016). Experimental Assessment of the Laryngeal Jet Effect on the Fluid Flow Pattern within the Trachea [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470386999

    APA Style (7th edition)

  • Salehi, Mehran. Experimental Assessment of the Laryngeal Jet Effect on the Fluid Flow Pattern within the Trachea. 2016. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470386999.

    MLA Style (8th edition)

  • Salehi, Mehran. "Experimental Assessment of the Laryngeal Jet Effect on the Fluid Flow Pattern within the Trachea." Doctoral dissertation, University of Toledo, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470386999

    Chicago Manual of Style (17th edition)

toledo1470386999
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This open access ETD is published by University of Toledo and OhioLINK.