Research Output
Articles
Publication Date: 2025
Environmental Modelling and Software (18736726)193
Accurately modeling the turbulence characteristics of wind flow entering urban areas is essential for improving the reliability of air pollution simulations, particularly when utilizing the LES approach. In this study, the Consistent Discrete Random Flow Generation method was implemented within the OpenFOAM software and evaluated for the first time in the context of solving concentration equation. A comparison of four inlet boundary conditions was conducted using wind tunnel experimental data. It was found that CDRFG presents more accurate results than the other methods, with an average error of 18 %. Then, the performance of the method in a complex geometry was evaluated by comparison with both experimental data and field measurements. The simulation demonstrated a high degree of accuracy in predicting the average dimensionless concentration, showing a close match with the experimental results, with a mean error of 16 %, and with the field measurements, exhibiting a mean error of 37 %. © 2025 Elsevier Ltd
Publication Date: 2025
Atmospheric Pollution Research (13091042)16(1)
Air pollution caused by traffic is a major contributor to unhealthy ambient air quality in the vicinity of urban highways and puts the health of residents and pedestrians at risk. Therefore, it is imperative to examine local pollution reduction methods. The present paper is concerned with Detached Eddy Simulation (DES) of an urban area with high concentration of air pollutants. As an example of a complex surrounding morphology, the studied domain encompasses a 2.5 km stretch of high-traffic highway, a bus terminal, and the nearby residential buildings. The numerical procedure is validated with some benchmark wind tunnel and numerical data. The locations of pollution accumulation have been identified and the effect of the ambient wind speed on the change of the maximum pollution concentration points has been investigated. Furthermore, potential pollution reduction strategies for such complex morphologies have been proposed based on the geometry change to prevent the formation of critical zones of pollution accumulation. The results show that critical zones are generally formed behind the walls of upstream buildings, adjacent to the upstream wall of the highway, and in front of the walls of downstream buildings. It was also found that changes in the ambient wind speed do not significantly alter the location of these critical zones. Furthermore, increasing the distance between adjacent buildings and the highway from 21 m to 30 m, can result in an average reduction of 76% in maximum carbon monoxide concentration values. An investigation into the impact of upstream buildings height indicates that reducing the height of certain buildings can effectively diminish pollution concentration to zero in residential areas and surrounding sidewalks. Additionally, increasing the depth of the highway and erecting 2 m solid barriers on either side of the highway are identified as two other effective techniques for reducing pollution concentration on both sides of the highway. The findings can be utilised to develop novel strategies aimed at enhancing air quality for residents and pedestrians. © 2024 Turkish National Committee for Air Pollution Research and Control
Publication Date: 2025
Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878)47(11)
This paper concerns with numerical performance evaluation of a refrigeration cycle with one, two and three-stage ejectors with an integrated ejector structure. The main innovation of this study lies in the integration of the stages in two-stage and three-stage ejectors into a single unified structure, and the numerical investigation of its impact on overall ejector performance compared to a conventional single-stage ejector. This approach simplifies the system, reduces manufacturing costs, enables operation at low absolute pressures, makes better use of the generator, and allows the system to be used under various evaporator operating conditions. Moreover, a comprehensive parametric study has been conducted on the influence of key geometrical parameters—including throat length, throat diameter, convergence angle, and mixing chamber length and area ratio in the second stage—on the performance of the two-stage ejector, which exhibited the highest coefficient of performance. Evaluation of Mach number and pressure variations along the ejector axes reveals that a two-stage ejector significantly enhances the performance of high-capacity refrigeration systems with low condenser pressure, achieving a 53.6% increase in the coefficient of performance. However, in the case of the three-stage ejector, high-pressure gradients at the inlets lead to increased pressure drops and irreversibility, resulting in a 26% decrease in performance compared to the single-stage ejector. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2025.
