Background: It is of clinical importance to examine the nasal cavity pre-operatively on surgical treatments. However, there is no simple and easy way to measure airflow in the nasal cavity. Objectives: Visualize the flow features inside the nasal cavity using computational fluid dynamics (CFD) method, and study the effect of different breathing rates on nasal function. Method: A three-dimensional nasal cavity model was reconstructed based on computed tomographic images of a healthy Malaysian adult nose. Navier-Stokes and continuity equations for steady airflow were solved numerically to examine the inspiratory nasal flow. Results: The flow resistance obtained varied from 0.026 to 0.124 Pa.s/mL at flow-rate from 7.5 L/min to 40 L/min. Flow rates by breathing had significant influence on airflow velocity and wall shear-stress in the vestibule and nasal valve region. Conclusion: Airflow simulations based on CFD is most useful for better understanding of flow phenomenon inside the nasal cavity.
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.
The aim of this study is to visualize and analyze the mucous layer effects towards the nasal airflow. Mucous layer had been neglected in previous works as it is considered a very thin layer along the nasal passageway. This paper discussed the effects in nasal airflow caused by the micrometer changes of the mucous layer thickness along the nasal passageway. Differences in maximum velocities caused by the mucous layer and visualization of the nasal airflow were studied. Computational fluid dynamics (CFD) was used to study three-dimensional nasal cavity of an adult Malaysian female. Six different models with various thickness of mucous layer within the range of 5–50 μm were implemented in the analysis with mass flow rate of 7.5 and 20 L/min. Mucous layer is assumed to be uniform, solid, and also stationary for this study. The results from all the six models were compared with the model with non-mucous effects. Based on both laminar and turbulent airflow simulations, it is shown that the addition of mucous layer thickness in analysis increased the maximum velocities at the four cross sections along the nasal cavity.
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