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Noise barriers play a crucial role in mitigating railway noise, with the aerodynamic pressure exerted by passing trains being a key factor in their structural design, particularly for those installed along high-speed railways. While previous studies have focused on the effects of train speed, geometry, and distance from the track centre, and have developed models incorporating these factors, limited attention has been given to the impact of bilateral layouts and barrier height on this pressure. Quantitative assessments of these two factors remain scarce, and existing pressure calculation models inadequately address their influence. This study addressed these gaps by employing computational fluid dynamics (CFD) simulations, validated by field test data, to qualitatively and quantitatively analyze the effects of barrier layout and height on the aerodynamic pressure acting on vertical noise barriers. The results demonstrate that two distinct transient pressure fluctuations over time are generated by the train's nose and tail, in agreement with the findings of the field tests. A bilateral layout increases peak pressure by up to 8.5%, particularly as the distance to the train centreline decreases. Moreover, increasing barrier height from 2 to 4 m resulted in a maximum pressure amplification of 13.23%, though the amplification rate diminished with further height increases. To address the limitations of existing pressure calculation models, an exponential model was developed to account for the amplification effect of bilateral layouts, while a logarithmic correction factor was introduced to account for barrier height. These models were integrated into a comprehensive aerodynamic pressure calculation framework, effectively capturing the combined impacts of barrier layout and height. Validated through simulations, the proposed model offers a more accurate and practical approach for predicting train-induced aerodynamic pressure on noise barriers, providing valuable insights to inform their structural design.

This textbook presents the basic methods, numerical schemes, and algorithms of computational fluid dynamics (CFD). Readers will learn to compose MATLAB programs to solve realistic fluid flow problems. Newer research results on the stability and boundedness of various numerical schemes are incorporated. The book emphasizes large eddy simulation (LES) in the chapter on turbulent flow simulation besides the two-equation models. Volume of fraction (VOF) and level-set methods are the focus of the chapter on two-phase flows.

In the present study, erosion wear of a 90o pipe bend has been investigated using the Computational fluid dynamics code FLUENT. Solid particles were tracked to evaluate the erosion rate along with k-ɛ turbulent model for continuous/fluid phase flow field. Spherical shaped sand particles of size 183 µm and 277 µm of density 2631 kg/m3 are injected from the inlet surface at velocity ranging from 0.5 to 8 ms-1 at two different concentrations. By considering the interaction between solid-liquid, effect of velocity, particle size and concentration were studied. Erosion wear was increased exponential with velocity, particles size and concentrations. Predicted results with CFD have revealed well in agreement with experimental results. The magnitude and location of maximum erosion wear were more severe in bend rather than the straight pipe.

The feeding shoe, which is a critical component that connects the rotary valve to the conveying pipeline, significantly influences the performance of powder conveying systems. The Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) was employed to investigate particle dynamics within various feeding shoe designs under gas–solid two-phase flow conditions. Through comparative analyses of two-phase flow characteristics and particle trajectories, three feeding shoe configurations, namely, through, horn, and funnel types, were evaluated, along with the effects of varying gas velocities. Key structural parameters, including opening diameter and inclination angle, were systematically examined to assess their effect on particle transport efficiency. Results demonstrated that feeding shoes with a low inclination angle or a small opening diameter exhibited poor particle flow, while those with a large opening diameter tended to induce backflow on the left side. By contrast, through-type feeding shoes with a large inclination angle and equal opening diameter achieved optimal conveying performance, minimizing backflow and enhancing flow efficiency. These findings provide theoretical insights for optimizing feeding shoe designs, improving conveying efficiency, and reducing production costs, offering valuable guidance for advancements in powder conveying technology and fluid mechanics.

Fluidized bed spray granulation is a process that facilities particle size enlargement by injecting solids in the form of a suspension, solution or melt. The produced particles are often of high value due to their highly specific, functionalized nature. This work provides a method for utilizing particle-scale simulations method like the coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) to predict the properties of particles produced in scaled-up apparatuses based on laboratory-scale experiments by correlating the conditions that particle experience to the properties they develop. Furthermore, a method for calibrating DEM models of weakly wetted particle systems by utilizing a novel, probabilistic liquid bridge state model is proposed.

This study analyzes the thermal performance of a 4.1 dm³ engine radiator through experimental tests and CFD simulations using ANSYS Fluent. The effects of materials, tube geometry, and flow conditions on heat transfer and thermal efficiency were evaluated. The results show that copper tubes enhance heat transfer by 18% but increase pressure drop by 4.44%. Additionally, increasing air velocity improves thermal efficiency by 3.74%, suggesting that specific improvements in fin design could enhance performance without increasing energy consumption. The study validates the use of CFD as a reliable tool for analyzing cooling systems in engines, benefiting the automotive industry with more efficient radiators. These improvements can be extended to hybrid and electric vehicles, as well as industrial heat exchangers, contributing to more sustainable thermal management. The main scientific contributions of this work are: (i) the experimental validation of a CFD model applied to an automotive radiator under transitional flow regime, (ii) the quantitative evaluation of the effects of copper tubes on thermal efficiency and pressure drop, and (iii) the detailed analysis of air velocity impact on heat transfer and its implications for radiator thermal design. Este estudio analiza el rendimiento térmico de un radiador de motor de 4.1 dm³ mediante pruebas experimentales y simulaciones CFD en ANSYS Fluent. Se evaluaron los efectos de materiales, geometría de tubos y condiciones de flujo en la transferencia de calor y eficiencia térmica. Los resultados muestran que los tubos de cobre mejoran la transferencia de calor en un 18%, pero aumentan la caída de presión en un 4.44%. Además, incrementar la velocidad del aire mejora la eficiencia térmica en un 3.74%, lo que sugiere que ciertas mejoras en el diseño de las aletas podrían aumentar el desempeño sin afectar el consumo energético. El estudio valida el uso de CFD como herramienta confiable para el análisis de sistemas de enfriamiento en motores, beneficiando a la industria automotriz con radiadores más eficientes. Estas mejoras pueden extenderse a vehículos híbridos y eléctricos, así como a intercambiadores de calor industriales, contribuyendo a una gestión térmica más sostenible. Las principales contribuciones científicas de este trabajo son: (i) la validación experimental de un modelo CFD aplicado a un radiador automotriz en régimen de flujo transitorio, (ii) la evaluación cuantitativa del efecto de los tubos de cobre sobre la eficiencia térmica y la caída de presión, y (iii) el análisis detallado del impacto de la velocidad del aire en la transferencia de calor y sus implicaciones en el diseño térmico del radiador.

The impact of drug delivery and particulate matter exposure on the human respiratory tract is influenced by various anatomical and physiological factors, particularly the structure of the respiratory tract and its fluid dynamics. This study employs computational fluid dynamics (CFD) to investigate airflow in two 3D models of the human air conducting zone. The first model uses a combination of CT-scan images and geometrical data from human cadaver to extract the upper and central airways down to the ninth generation, while the second model develops the lung airways from the first Carina to the end of the ninth generation using Kitaoka’s deterministic algorithm. The study examines the differences in geometrical characteristics, airflow rates, velocity, Reynolds number, and pressure drops of both models in the inhalation and exhalation phases for different lobes and generations of the airways. From trachea to the ninth generation, the average air flowrates and Reynolds numbers exponentially decay in both models during inhalation and exhalation. The steady drop is the case for the average air velocity in Kitaoka’s model, while that experiences a maximum in the 3rd or 4th generation in the quasi-realistic model. Besides, it is shown that the flow field remains laminar in the upper and central airways up to the total flow rate of 15 l/min. The results of this work can contribute to the understanding of flow behavior in upper respiratory tract. Graphical Abstract

In this numerical study, the variations in the surface area of the cooling channels in a solid oxide fuel cell with different cross sections and multi-walled carbon nanotubes oil/MWCNT nanofluid volume fractions are considered. Rectangular, trapezoidal and elliptical cross sections, and nanofluid volume fractions of 0–6% for the fluid are chosen as the studied parameters as well as the mass flow rates. In this research, a 3D model is developed by the finite volume method using the computational fluid dynamics (CFD). Then, the flow field and the heat transfer rate are predicted. The results show that the dissipated heat in the fuel cell is dependent on the mass flow rate of the fluid. That increased heat increases the heat transfer rate. The presence of the solid particles can also reinforce the heat conduction of the coolant fluid and consequently improve the heat transfer performance. The pumping power is maximum for the highest mass flow rate and the highest solid nanoparticle volume fractions. Additionally, the pumping power is dependent on the route in which the sections with lowest momentum changes and lowest pressure drops have the least amount of the pumping power. The ratio of the dissipated heat by the nanofluid over the base fluid is compared to a pressure drop. The movement of flow with the lower mass flow rates will result in penetrations of the thermal boundary layers into different flow regions, which can increase the optimum temperature in the solid part of the fuel cell. By increasing the mass flow rate of the fluid passing through the channels from 0.002 to 0.004 kg s−1, the maximum temperature is decreased by 6.13, 3.34 and 6.35% for rectangular, trapezoidal and elliptical channels, respectively.

The transient hydrodynamic lubrication model of tilting pad journal bearings (TPJBs) was established by the computational fluid dynamics (CFD) method and the self-developed dynamic grid program. The fluid-structure interaction between the flow field and the rotor motion, the pads rotations was realized. The feasibility of the model is proved by comparing with the experimental data. The dynamic response of TPJBs under the various unbalance, the loading modes and the rotating speeds was studied. The dynamic response of TPJBs is further analyzed through a research of the relationships among the shaft whirl orbits, transient force acting on the shaft, rotation angles of the pads and transient oil film force of the pads. With the increase of unbalance, the whirl orbits expand and whirl orbits centers rise continuously. The whirl orbits and orbit center attitude angles of TPJBs are smaller than those of fixed-pad journal bearings. Compare with the load between pads, the whirl orbits are smaller and whirl orbits centers drop slightly under the load on pads. With the increase of rotating speed, the whirl orbits expand nonlinearly, whirl orbit center rises nonlinearly. The transient force acting on the shaft, the rotation angles of the pads and the transient oil film force of the pads change periodically, and the period and frequency of these changes are the same as that of the shaft rotation. The maximum force acting on the shaft appear before the maximum shaft center position (the vertexes of the whirl orbit).