CFD Modelling of Air Flow and Fine Powder Deposition in the Respiratory Tract
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CFD modelling of air flow and fine powder deposition in the respiratory tract Yun Hwan Kim A thesis in fulfilment of the requirements for the degree of Master of Philosophy School of Materials Science and Engineering Faculty of Science April 2017 THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Kim First name: Yun Hwan Other name/s: Abbreviation for degree as given in the University calendar: M.Phil. School: School of Materials Science and Engineering Faculty: Science Title: CFD modelling of air flow and fine powder deposition in the respiratory tract Abstract This project was to investigate and observe characteristics of micro particles suspended in the ambient air or pharmaceutical aerosols with respect to the mechanisms of deposition in human airways under different inspiratory conditions. Such determination includes pattern observations of inspiratory flow-field of the air, particle trajectory during inspiratory conditions and particle deposition. Computational fluid dynamic (CFD) was employed to simulate above problems, aiming to observe flow-field of the inspiratory air and characteristic of flow turbulence in the respiratory tract as well as particle behaviour in the respiratory tract regarding to the particle deposition. In order to do so, three different airway models were employed for the simulations: two realistic airway models introduced by Kitaoka and Weibel airways model. The motion of micro-sized particles between 1~20 µm were simulated under the steady state two inlet- inspiratory conditions – inhalation condition (60 L/min) and breathing condition (18 L/min); to evaluate deposition efficiency. Inertial impaction was dominantly caused high density deposition of particles in upper tracheobronchial region, particularly in regions where daughter airways bifurcate. Results also showed that the velocity in the first bifurcation of airway was higher than the inlet velocity. Back pressures were been observed in lower generations, and high pressures were been observed at every bifurcation regions. The increase of velocity was observed where the fluid directions rapidly changed. Turbulence kinetic energy was the least in main bronchus of respiratory tract and fluctuated from generation to generation. In Kitaoka’s generation 0-7 model, deposition fractions of 2 µm, 6 µm and 10 µm particles were 6.6%, 60.7% and 91.5% respectively under inhalation condition whereas deposition fractions of such particles were 2.9%, 9.0% and 44.9% under breathing condition. In Kitaoka’s generation 0-11 model, deposition fractions of 2 µm, 6 µm and 10 µm particles were 30.9%, 80.1% and 99.8% respectively under inhalation condition whereas deposition fractions of such particles were 16.2%, 24.4% and 62.6% under breathing condition. Furthermore in Weibel’s generation 3-6 model, deposition fractions of 2 µm, 6 µm and 10 µm particles were 9.7%, 38.3% and 97.4% respectively under inhalation condition whereas deposition fractions of such particles were 3.2%, 15.6% and 56.2% under breathing condition. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). …………………………………………………………… ……………………………………..……………… ……….……………………...…….… Signature Witness Signature Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed …………………………………………………… Date ……………………………………………………… i ACKNOWLEDGEMENT First of all, I would like to greatly thank my LORD Jesus Christ, for giving me the opportunity allowing me to undertake the great piece of research under the great supervisor, Professor Runyu Yang, for the purposes of fulfilling His great plan in my life. Also, I was so blessed to have tremendous support from my parents and friends. I would not be standing at where I am without your endless understanding and encouragements. “The fear of the LORD is the beginning of the knowledge, and the heart of the discerning acquires knowledge, for the ears of the wise seek it out.” – King Solomon’s Proverbs – ii ABSTRACT This project had the objective to investigate and observe characteristics of micro particles suspended in the ambient air or pharmaceutical aerosols with respect to the mechanisms of deposition in human airways under different inspiratory conditions. Such determination includes pattern observations of inspiratory flow-field of the air, particle trajectory during inspiratory conditions and particle deposition. All those results are relevant to diversified fields as its applicable scope is not limited to the pharmaceutical aerosol devices development but also to the environmental study and combustion development. Computational fluid dynamic (CFD) was employed to simulate above problems, aiming to observe flow-field of the inspiratory air and characteristic of flow turbulence in the respiratory tract as well as particles behaviour in the respiratory tract regarding to the particle deposition. In order to do so, three different airway models were employed for the simulations: two realistic airway models introduced by Kitaoka and one idealised airway model based on the morphological study of Weibel that was widely utilized for both numerical and experimental studies of particle deposition in human airways. Two realistic airway models of Kitaoka correspond to generation 0-7 and 0-11 respectively, whereas the idealised airway model corresponds to generation 3-6. Those three airway models are a portion of upper tracheobronchial region which the boundary of realistic airway models both start from trachea whereas idealised airway model starts from bronchiolus. Generation 0-7 and 0-11 model corresponds from trachea to 7th airway bifurcations and from trachea to 11th airway bifurcations in tracheobronchial region respectively, and generation 3-6 model corresponds to an airway portion from 3rd airway bifurcation to 6th airway bifurcation. The motion of micro-sized particles between 1~20 µm were simulated under two inlet- inspiratory conditions – induced inhalation condition (60 L/min) and normal breathing condition (18 L/min) to evaluate deposition efficiency. The flow-field and fluid momentum generated in realistic airway models under both conditions have shown direct influence to the motion of the inhaled particles. Inertial impaction was dominantly caused high density deposition of particles in upper tracheobronchial region particularly in regions where daughter airways bifurcate. Results also have shown that iii the velocity in the first bifurcation of airway was higher than the inlet velocity. Back pressures were been observed in lower generations, and high pressures were been observed at every bifurcation regions. Fluid velocity gradually decreased toward the outlets and the increase of velocity was observed where the fluid directions rapidly changed. Turbulence kinetic energy was shown to be the least in main bronchus of respiratory tract and fluctuated from generation to generation. Furthermore, the aerodynamic sizes of particles were also highly related to the variation of deposition efficiency, as greater size particles caused higher rate of particle deposition. In generation 0-7 realistic airways model, deposition fractions of 2 µm, 6 µm and 10 µm particles were 6.6%, 60.7% and 91.5% respectively under inhalation condition, whereas deposition fractions of such particles were 2.9%, 9.0% and 44.9% under breathing condition. In generation 0-11 realistic airways model, deposition fractions of 2 µm, 6 µm and 10 µm particles were 30.9%, 80.1% and 99.8% respectively under inhalation condition, whereas deposition fractions of such particles were 16.2%, 24.4% and 62.6% under breathing condition. Furthermore in generation 3- 6 idealised airways model, deposition fractions of 2 µm, 6 µm and 10 µm particles were 9.7%, 38.3% and 97.4% respectively under inhalation condition, whereas deposition