Semester

Spring

Date of Graduation

2007

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Ismail B. Celik

Committee Co-Chair

Ibrahim Yavuz.

Abstract

The airborne transmission of diseases is of great concern to the public health community. The possible spread of infectious disease by aerosols is of particular concern among health-care workers and emergency responders, who face a much greater risk of exposure to these hazards than does the general public. Some diseases, such as influenza, spread by dissemination and inhalation of aerosols of small droplet nuclei that are generated by coughing and remain airborne for an extended time. For that reason a better understanding of the generation of aerosols is important. Therefore, the main objective of this study is to investigate the flow dynamics and the aerosol generation during coughing. This research aims to develop a fairly simple yet an accurate model for the flow simulation in the upper respiratory tract, mainly in the larynx, and the number and size distribution of the aerosols generated during coughing.;In order to provide a more complete analysis tool, a secondary objective is to develop a simple reduced order model for the purpose of simulating the air flow and particle dynamics in the larynx. To this end a pseudo two-dimensional model (PTM) has been developed and run for several cases including, sinusoidal laminar and low Reynolds number flow cases including breathing and coughing. The comparison of the PTM model results with FLUENT has shown that the PTM model is capable of producing accurate results within a fraction of execution time needed for the multi-dimensional FLUENT's model.;The aerosol generation and entrainment model (AGEM) is integrated into this validated one-dimensional model. This is done by utilizing a one dimensional turbulent kinetic energy equation. AGEM is then employed to calculate the aerosol formations during a cough, which is simulated by the one dimensional flow solver. The final size distribution of the aerosol droplets is calculated and these findings are compared with laboratory measurements. It is shown that, with appropriate model coefficients, it is possible to obtain size distribution of aerosols that is consistent with the experimental findings. A parametric study by variation of physical properties of the mucus has also been carried out. The results show some interesting trend with changing surface tension and varying cough signals.;This study may be considered as a step towards a more complete understanding of aerosol generation mechanisms by coughing, which in turn lead to airborne transmission of diseases. The simulation tools developed should serve the scientist to do more parametric studies in a fairly quick manner and investigate the aerosol dispersion in the confined areas as well as studying particle deposition patterns within the upper respiratory track.

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