Computational Fluid Dynamics Study Of Nasal Cavity Model

Understanding the properties of airflow in the nasal cavity is very important in determining the nasal physiology and in diagnosis of various anomalies associated with the nose. Inter-human anatomical variation for the nasal cavity exists and also differences on physiological morphology are observed based on gender. No specific numerical modeling studies have been carried out to compare and ascertain the effect of gender on flow variable inside the nasal cavity. Also numerical modeling involves various simplifications, for example the postural effect and appropriate boundary conditions which affect the outcome of the airflow studies. The present work involves development of three-dimensional nasal cavity models using computed tomographic images of healthy Malaysian females. A steady state continuity and Navier stoke equations were solved for both inspiratory and expiratory mechanism with flow rates ranging from 7.5 to 15 L/min as laminar and 20 to 40 L/min studies were simulated depicting turbulent flow conditions. Computational fluid dynamics (CFD) analysis provided effective visualization of the flow features inside the nasal cavity. The comparison between inspiratory and expiratory mechanism and the effect of different breathing rates on nasal function have been presented. The value of maximum wall shear stress at the vestibule region increased by more than 2000 % as the flow rate increased from 7.5 to 40 L/min. The complicated anatomy of the nasal cavity has been naturally designed to attain the physiological function desired to facilitate normal breathing. The xix current study has identified certain gender based anatomical and physiological differences. The use of computational fluid dynamic has assisted in the understanding of these differences which could not be earlier quantified based on mere medical observation and measurement devices. The influence of postural changes in nasal cavity has also been investigated. Around 0.3% change in the average static pressure is observed while changing from sitting to supine position. The change in the direction of gravity due to change of posture significantly influences the flow parameters and hence should be considered in all future studies involving nasal flow. Most of the researchers employ plug flow boundary definitions to address the flow problems associated with nasal flow. This study has revealed the fallacy of such a definition and found significant differences in values obtained in either case. Comparative study of the pull flow model and the plug flow model has found significant variations highlighting the need for using the right boundary conditions. At the nasal valve, the resistance for plug flow was 0.311 Pa-min/L and for pull flow the value was 0.147 Pa-min/L. Maximum variation was noticed at the vestibule region with 0.3578 Pa-min/L. The average velocity for nasal vestibule and nasal valve is 1.4m/s and 1.6m/s for plug flow. Whereas, for pull flow case, the average velocity value in nasal vestibule and nasal valve region was observed to be around 0.96m/s and 1.41m/s respectively. A correct approach therefore to the numerical model is the pull flow model, which more directly represents the physiological inspiratory mechanism

Computational Fluid Dynamics Study Of Nasal Cavity Model

Understanding the properties of airflow in the nasal cavity is very important in determining the nasal physiology and in diagnosis of various anomalies associated with the nose. Inter-human anatomical variation for the nasal cavity exists and also differences on physiological morphology are observed based on gender. No specific numerical modeling studies have been carried out to compare and ascertain the effect of gender on flow variable inside the nasal cavity. Also numerical modeling involves various simplifications, for example the postural effect and appropriate boundary conditions which affect the outcome of the airflow studies

疾患鼻気道における空気流と粒子堆積の計算流体力学的研究

九州工業大学博士学位論文（要旨）学位記番号：生工博甲第315号 学位授与年月日：平成30年3月23

疾患鼻気道における空気流と粒子堆積の計算流体力学的研究

Understanding the properties of airflow in the nasal cavity is very important in determining the nasal physiology and in diagnosis of various anomalies associated with the nose. The complex anatomy of the nasal cavity has proven to be a significant obstacle in the understanding of nasal obstructive disorders. Due to their non-invasiveness, Computational Fluid Dynamics (CFD) has now been utilized to assess the effects of surgical interventions on nasal morphological changes as well as local breathing airflow characteristics through the upper airway of individual patients. Furthermore, nasal inhalation is a major route of entry into body for airborne pollutions. Therefore, the function of the upper airway to filter out the inhaled toxic particles is considered important. The determination of the total particle filtering efficiency and the precise location of the induced lesion in the upper airway is the first step in understanding the critical factors involved in the pathogenesis of the upper airway injury. The present work involved development of three-dimensional diseased upper airway models from Computed Tomographic (CT) scan images derived from a nasal airway without any nasal diseased and an upper airway which was diagnosed with chronic nasal obstruction and obstructive sleep apnea. Numerical simulation of airflow and transport and deposition of inhaled pollutant through chronic diseased nasal airway, constricted pharyngeal representing Obstructive Sleep Apnea (OSA) and diseased upper airway with OSA for pre- and post-operative cases have been studied. Detailed flow pattern and characteristics for inspiratory airflow for various breathing rates (7.5-40 L/min) were evaluated. Simulation of the particle transport and deposition of micro-sized particles with particle diameter ranging from 1-40 ?m were also investigated. In the first part of this study, the surgical treatment performed in the nasal cavity which include septoplasty, inferior turbinate reduction and partial concha bullosa resection substantially increased nasal volume, which influenced flow partitioning and decreases the pressure drop and flow resistance of the nasal passage. The removal of the obstruction in the nasal airway significantly improve the breathing quality. However, the nasal airway experienced approximately about a 50 % decrease in total particle filtering efficiency after surgery. Therefore, careful consideration should be given to this matter before nasal operation especially for a patient with breathing allergic history. In the second part of this study, the morphology of the constricted pharyngeal representing OSA was found to significantly affect the airflow pattern and the deposition fraction of microparticles. The morphology of the upper airway, the size of the inhaled particle and breathing rate was found significantly affect the total particle deposition efficiency and local deposition fraction in the upper airway. The presented regional deposition fraction may be used in specifying the site of highest possibility for respiratory lesions according to the breathing rate and the size of the inhaled toxic particles. Results obtained from this study can be also used to estimate the location of airway obstruction in upper airway of patient with sleep apnea symptom. In the third part of this study, the surgical conducted procedure has cleared out the obstructions in the nasal airway hence improve the airflow distribution through the upper airway during inhalation process. This study shows that the nasal surgery alone can help improve the breathing quality in the upper airway with OSA. The reduction of the airflow resistance in the nasal cavity affect the pressure distribution in the lower part of the upper airway. Obstruction in the nasal passage and sudden airway expansion in the upper airway increased number of particles trap, recirculated and finally deposited in the airway. Finally, the experimental data obtained from the experimental study utilizing the developed pharyngeal airway further validate the result obtained from the numerical study.九州工業大学博士学位論文 学位記番号：生工博甲第315号 学位授与年月日：平成30年3月23日1: INTRODUCTION|2: LITERATURE REVIEW|3: MODELLING THE HUMAN UPPER AIRWAY|4: NUMERICAL SIMULATION METHODOLOGY|5: NUMERICAL INVESTIGATION ON AIRFLOW CHARACTERISTICS IN NASAL CAVITY HAVING TURBINATE HYPERTROPHY, CONCHA BULLOSA, AND SEPTUM DEVIATION WITH OSA: PRE- AND POST SURGERY|6: COMPUTATIONAL FLUID DYNAMICS STUDY OF AIRFLOW AND MICROPARTICLE DEPOSITION IN A CONSTRICTED PHARYNGEAL SECTION REPRESENTING OBSTRUCTIVE SLEEP APNEA DISEASE|7: NUMERICAL SIMULATION OF AIRFLOW AND AEROSOL DEPOSITION IN REALISTIC HUMAN UPPER AIRWAY WITH OBSTRUCTIVE SLEEP APNEA AND CHRONIC NASAL OBSTRUCTION: PRE- AND POST-SURGERY|8: EXPERIMENTAL INVESTIGATION|9: CONCLUSIONS AND FUTURE RECOMMENDATIONS九州工業大学平成29年

A review on the impact of aircraft cabin air quality and cabin pressure on human wellbeing

Airliner cabins present more complicated scenario due to different design and operation challenges owing to the extreme environmental conditions, complexity of the operational systems, and the authorities that govern such environments. The scientific evaluation is rendered difficult due to lack of empirical evidence determining the airliner cabin air quality as well as consequent health effects occurring due to short or long flight exposure. Crew members and passengers report dizziness, fatigue, headaches, sinus and ear problems, dry eyes and sore throats during and after travel. There are persistent concerns about the transmission of infectious agents such as influenza, tuberculosis and measles viruses during flights. Moreover, a systematic collection of data related to airplane environmental exposures is not yet available and the effects of environmental conditions on wellbeing of travelers and their comfort level are yet to be fully ascertained. In this work, a systematic review of the air quality inside the airliner cabin are discussed. The potential pollutants and their established causes are discussed. In addition to this, major health discomforts faced by the occupants are presented

Computational fluid dynamics study of pull and plug flow boundary condition on nasal airflow

The recent advances in the computer based computational fluid dynamics (CFD) software tools in the study of airflow behavior in the nasal cavity have opened an entirely new field of medical research. This numerical modeling method has provided both engineers and medical specialists with a clearer understanding of the physics associated with the flow in the complicated nasal domain. The outcome of any CFD investigation depends on the appropriateness of the boundary conditions applied. Most researchers have employed plug boundary condition as against the pull flow which closely resembles the physiological phenomenon associated with the breathing mechanism. A comparative study on the effect of using the plug and pull flow boundary conditions are evaluated and their effect on the nasal flow are studied. Discretization error estimation using Richardson's extrapolation (RE) method has also been carried out. The study is based on the numerical model obtained from computed tomographic data of a healthy Malaysian subject. A steady state Reynold averaged Navier–Stokes and continuity equations is solved for inspiratory flow having flow rate 20 L/min representing turbulent boundary conditions. Comparative study is made between the pull and plug flow model. Variation in flow patterns and flow features such as resistance, pressure and velocity are presented. At the nasal valve, the resistance for plug flow is 0.664 Pa-min/L and for pull flow the value is 0.304 Pa-min/L. The maximum velocity at the nasal valve is 3.28 m/s for plug flow and 3.57 m/s for pull flow model

Computational fluid dynamics study of airflow and particle deposition in diseased nasal airway

Understanding the properties of airflow in the nasal cavity is very important in determining the nasal physiology and in diagnosis of various anomalies associated with the nose. The complex anatomy of the nasal cavity has proven to be a significant obstacle in the understanding of nasal obstructive disorders. Due to their non-invasiveness, Computational Fluid Dynamics (CFD) has now been utilized to assess the effects of surgical interventions on nasal morphological changes as well as local breathing airflow characteristics through the upper airway of individual patients. Furthermore, nasal inhalation is a major route of entry into body for airborne pollutions. Therefore, the function of the upper airway to filter out the inhaled toxic particles is considered important. The determination of the total particle filtering efficiency and the precise location of the induced lesion in the upper airway is the first step in understanding the critical factors involved in the pathogenesis of the upper airway injury. The present work involved development of three-dimensional diseased upper airway models from Computed Tomographic (CT) scan images derived from a nasal airway without any nasal diseased and an upper airway which was diagnosed with chronic nasal obstruction and obstructive sleep apnea. Numerical simulation of airflow and transport and deposition of inhaled pollutant through chronic diseased nasal airway, constricted pharyngeal representing Obstructive Sleep Apnea (OSA) and diseased upper airway with OSA for pre- and post-operative cases have been studied. Detailed flow pattern and characteristics for inspiratory airflow for various breathing rates (7.5-40 L/min) were evaluated. Simulation of the particle transport and deposition of micro-sized particles with particle diameter ranging from 1-40 μm were also investigated. In the first part of this study, the surgical treatment performed in the nasal cavity which include septoplasty, inferior turbinate reduction and partial concha bullosa resection substantially increased nasal volume, which influenced flow partitioning and decreases the pressure drop and flow resistance of the nasal passage. The removal of the obstruction in the nasal airway significantly improve the breathing quality. However, the nasal airway experienced approximately about a 50 % decrease in total particle filtering efficiency after surgery. Therefore, careful consideration should be given to this matter before nasal operation especially for a patient with breathing allergic history. In the second part of this study, the morphology of the constricted pharyngeal representing OSA was found to significantly affect the airflow pattern and the deposition fraction of microparticles. The morphology of the upper airway, the size of the inhaled particle and breathing rate was found significantly affect the total particle deposition efficiency and local deposition fraction in the upper airway. The presented regional deposition fraction may be used in specifying the site of highest possibility for respiratory lesions according to the breathing rate and the size of the inhaled toxic particles. Results obtained from this study can be also used to estimate the location of airway obstruction in upper airway of patient with sleep apnea symptom. In the third part of this study, the surgical conducted procedure has cleared out the obstructions in the nasal airway hence improve the airflow distribution through the upper airway during inhalation process. This study shows that the nasal surgery alone can help improve the breathing quality in the upper airway with OSA. The reduction of the airflow resistance in the nasal cavity affect the pressure distribution in the lower part of the upper airway. Obstruction in the nasal passage and sudden airway expansion in the upper airway increased number of particles trap, recirculated and finally deposited in the airway. Finally, the experimental data obtained from the experimental study utilizing the developed pharyngeal airway further validate the result obtained from the numerical study

Computational fluid dynamics study in biomedical applications: a review

Computational Fluid Dynamics (CFD) is a widely adopted methodology of computer-based simulation in order to solve complex problems in many modern engineering fields as well as biomedical field. CFD is becoming a key component in developing updated designs and optimization through computational simulations, resulting in lower operating costs with enhanced efficiency. Even though biomedical application is pertaining to the complexity of human anatomy and human body fluid behaviour, the recent CFD in biomedical application is more accessible and practicable due to the availability of high performance hardware and software with advances in computer sciences. Many simulations and clinical results have been used to study the analyses in biomedical applications, particularly in blood flow and nasal airflow. The study of blood flow analysis includes the circulation of blood of ventricle function, coronary artery and heart valves. Meanwhile, the nasal airflow analysis consists of the basic airflow in human nose, drug delivery improvement and virtual surgery. Therefore, this review discusses the essential methodology of CFD as a reliable tool for researchers and medical scientist in understanding the physiology and pathophysiology of cardiovascular system and respiratory system through simulation. CFD plays a major role as a decision support prior to undertaking a real commitment to execute any medical design alterations and provide the direction to develop medical interventions

CFD analysis of mucous effect in the nasal cavity

This research aims to investigate the airflow patterns and particle deposition in a healthy human upper airways. A realistic 3-D computational model of the upper airways including the vestibule was developed using a series of CT scan images of a healthy human. Simulations of the airflow fields in the upper airway passages were performed by solving the Navier-Stokes and continuity equations for breath rate 20 L/min. The trajectory analysis approach was applied to study the particle transport and deposition for the model with and without mucous lining. The presented results revealed that the mucous layer can have significant impact on airflow analysis and there were noticeable differences in the amount of particle deposition in each models