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The computational fluid dynamics (CFD) are used to evaluate the physiological function of the nose. We evaluated the aerodynamics of the nasal cavity in a patient with septal perforation (SP), pre- and postvirtual repair. Three-dimensional nasal models were reconstructed, and then a wide range of the pressure drops and flow rates were analyzed. The airflow velocity is higher in the central region and is lower around the boundary of the SP. The air velocity in the SP increases as the pressure drop increases. Furthermore, at the anterior part of the SP, the shear stress is higher in the upper part. In addition, the repair of SP does not affect the total nasal airflow rate and the velocity contour patterns. The potential usage of the CFD technique as a predictive technique to explore the details and a preoperative assessment tool to help in clinical decision making in nasal surgery is emphasized.

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a b s t r a c tThis article investigates the dispersion of airborne pollutants emitted from different locations near a high-rise building. A Computational Fluid Dynamics (CFD) model for simulating the wind flow field and the pollutant dispersion was developed and validated by wind tunnel data. Then the spreading of the pollutant emitted from different locations to a rectangular-shaped high-rise residential (HRR) building was numerically studied. The pollutant source location was set in a wide range of the position angle and distance between the source and the building. It was found that the pollutant concentration on the building decreases with an increase in the emission distance whereas the effect of the position angle is more complicated. Interestingly, there is a critical range of the position angle from which the emitted pollutants will not spread to the building in a significant way. The effect of the source location was linked to the wind flow field around the building, particularly with several major flows. The vertical distributions of the pollutant concentration on different faces were also investigated, and it was found that these are more affected by the vertical flow near each face. Finally, a mathematical model was developed to evaluate the pollutant concentration as a function of the emission distance and position angle. These findings are helpful to the understanding of the dispersion of airborne pollutants around high-rise buildings and the related hazard management in urban design. et al. / Applied Mathematical Modelling 81 (2020) 582-602 583 Rising reports of such outbreaks have attracted scientific attention on understanding the spreading of airborne hazards in urban areas, which is helpful for the prediction and control of the outbreak of airborne diseases for public health [7][8][9][10][11] .The pollutant outbreaks are riskier near high-rise residential (HRR) buildings due to the high population density [12] . Additionally, the spreading of pollutants around and inside such buildings is more complex as a result of strong windstructure interactions and diverse spreading scenarios. Pollutants may be emitted from an HRR building (e.g. from a kitchen exhaust) and spread to the same building at different positions [13 , 14] , like the possible SARS spreading in typical HRR buildings in Hong Kong [15][16][17] . Pollutants may also be released from sources located around a HRR building at lower levels [18][19][20][21][22] , such as the evaporative facilities (e.g. cooling tower or air scrubber) of public facilities, which have been responsible for reported disease outbreaks [23][24][25] . Accordingly, the position of the potential pollutant source is an important factor in evaluating the risk of the spreading of pollutants near an HRR building, but it has not been fully evaluated in terms of the distance and the position angle between the source and the building.The spreading of pollutants in urban areas has been studied using various methods. Wind tunnel is a valuable tool in studying such...

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