Mohammed Zubair

Airflow inside the nasal cavity: visualization using computational fluid dynamics.

Abstract 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.

Hybrid Mesh for Nasal Airflow Studies

The accuracy of the numerical result is closely related to mesh density as well as its distribution. Mesh plays a very significant role in the outcome of numerical simulation. Many nasal airflow studies have employed unstructured mesh and more recently hybrid mesh scheme has been utilized considering the complexity of anatomical architecture. The objective of this study is to compare the results of hybrid mesh with unstructured mesh and study its effect on the flow parameters inside the nasal cavity. A three-dimensional nasal cavity model is reconstructed based on computed tomographic images of a healthy Malaysian adult nose. Navier-Stokes equation for steady airflow is solved numerically to examine inspiratory nasal flow. The pressure drop obtained using the unstructured computational grid is about 22.6 Pa for a flow rate of 20 L/min, whereas the hybrid mesh resulted in 17.8 Pa for the same flow rate. The maximum velocity obtained at the nasal valve using unstructured grid is 4.18 m/s and that with hybrid mesh is around 4.76 m/s. Hybrid mesh reported lower grid convergence index (GCI) than the unstructured mesh. Significant differences between unstructured mesh and hybrid mesh are determined highlighting the usefulness of hybrid mesh for nasal airflow studies.

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 Richardsons 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.

Static Thrust Measurement of Two Types of Perforated Solid Propellant Grain Configurations

AbstractA laboratory scale experimental setup has been developed to explore an alternative source of solid propellant. A combination of potassium nitrate and ferric oxide embedded in epoxy binder constitutes the ingredients of the propellant used. A scanning electron microscope and nondestructive test (X-ray radiography) were utilized to study the crack surface and internal structure of the cured propellants. The influence of the epoxy mixing ratio on the sample density has been studied. Two solid propellant grain configurations were utilized to study the performance characteristics in terms of the thrust generated. It was found that the manufacturer’s mixing ratio provided the optimum density results for the given set of configurations tested. The multiperforated grain configuration showed higher performance in terms of trust when compared with the single perforated grain configuration.

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.