Article
Engineering, Marine
Rui You, Spyros A. Kinnas
Summary: The k-ε SST turbulence model is implemented in the VIScous and Vorticity Equation method, allowing it to solve turbulent flows independently. The method utilizes the Finite Volume Method for the discretization of the vorticity equation and the turbulence model. Its advantages include requiring a small computational domain, automatically satisfying the continuity equation, and allowing for pressure calculation after solving for the flow field. The method is applied to turbulent flows over a 2D hydrofoil and a hydrofoil with a cupped trailing edge, showing good agreement with a Reynolds-Averaged Navier-Stokes solver and the capability to predict turbulent flows at high Reynolds numbers and separated flows.
Article
Mechanics
A. Capone, G. Moscato, G. Romano
Summary: The behavior of dispersed particles in a turbulent round jet is experimentally investigated. The role of particle-to-fluid density ratio rho(p)/rho(f) in particle velocity field structure and preferential concentration is analyzed. The results show that increasing particle density leads to larger departure from uniformity. This effect is limited to the region X / D < 5, where the largest differences in average and fluctuating velocities with respect to the unladen case are observed.
Article
Engineering, Chemical
Hui Cai, Guoqing Miao
Summary: This study reported the flow pattern in a vertically vibrated, annular, and granular system, showing either laminar granular flow or turbulent granular flow in different vibration modes. The flow patterns were explained and identified using the Reynolds numbers of the granular system. The results revealed a property peculiar to the granular flow similar to, yet different from, viscous fluids.
Article
Mechanics
Vijit Rathore, Subhasish Dey, Nadia Penna, Roberto Gaudio
Summary: This study investigates the turbulent flow characteristics over an abrupt step change in bed roughness using a Particle Image Velocimetry system, revealing the impact of bed roughness on the flow field. Key findings include changes in Reynolds stresses and bed shear stresses in response to the abrupt change in bed roughness, as well as the creation of a roughness-induced layer that grows over the downstream bed. Bursting analysis suggests that sweeps govern the near-bed flow on the downstream bed, while ejections prevail far from the bed.
Article
Mechanics
Xiao-Ping Chen, Deng-Song Huang, Shuo Zhao, Chen-Shao Zhu
Summary: This study conducts direct numerical simulations to investigate the influence of compressibility effects on turbulent statistics and large-scale structures in temporally evolving turbulent channel flows with a weak spanwise rotation. The results show that compressibility has some impact on the turbulent statistics distributions, but many asymmetric characteristics still exist.
Article
Engineering, Mechanical
Liuzhen Ren, Haibao Hu, Luo Xie, Suhe Huang, Luyao Bao, Xiao Huang
Summary: This paper investigates the drag reduction effect of polymer injection in turbulent flow, finding that as the speed increases, the drag reduction efficiency also increases.
EXPERIMENTS IN FLUIDS
(2021)
Article
Engineering, Aerospace
Congcong Chen, Zhuo Wang, Lin Du, Dakun Sun, Xiaofeng Sun
Summary: By using the turbulent wall model and hierarchical Cartesian grid, researchers successfully simulated unsteady flows in turbomachines with the immersed boundary method. Through verification under different conditions, the effectiveness of this method was validated, with results matching well with experimental data. This approach can be effectively applied to simulating unsteady flows in turbomachines.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Mechanics
XianXu Yuan, YaLu Fu, JianQiang Chen, Ming Yu, PengXin Liu
Summary: In this study, the effects of spanwise-oriented grooves on the kinetic and thermodynamic statistics in a supersonic turbulent channel flow were investigated using direct numerical simulations. The results showed that these grooves induced compressive and expansive waves that traveled across the channel and influenced the distribution of vortices and streaks. These waves enhanced the fluctuations in temperature, density, and pressure, and also altered the correlations between velocity and temperature.
Review
Engineering, Aerospace
William J. Devenport, K. Todd Lowe
Summary: This article presents a review of historical and recent developments in the understanding of equilibrium and non-equilibrium turbulent boundary layers at incompressible high-Reynolds number conditions. The review focuses on the mean flow, turbulence stress fields, and instantaneous structure, discussing smooth wall and rough wall boundary layers as well as equilibrium and non-equilibrium two-dimensional flows. It concludes with a detailed discussion of boundary layer development in skewed, three-dimensional flows over smooth walls.
PROGRESS IN AEROSPACE SCIENCES
(2022)
Article
Engineering, Multidisciplinary
Praveen J. Sanga, Arbind Kumar, Sabin K. Mishra
Summary: A numerical study was conducted to investigate the thermal and flow fields of a two-dimensional vented cavity under forced convection turbulent flow. The study found that the top curved wall surface has significant effects on heat transfer performance in different configurations of inlet and outlet ports. Increasing the height of the curved surface enhances heat transfer, but also leads to relatively high pressure drop. On the other hand, the semi-elliptical top surface cavity with inlet and outlet ports positioned on the same axis exhibits better heat transfer performance.
ENGINEERING APPLICATIONS OF COMPUTATIONAL FLUID MECHANICS
(2022)
Article
Engineering, Geological
Hong Fang, Jianting Zhu, Jinrong Qiu, Yaoming Su, Di Xia
Summary: Using laminar or turbulent flow equations indiscriminately to describe groundwater flows in fracture networks may result in large errors. This study proposes a new method that separates laminar and turbulent flows in individual fractures to simulate steady-state groundwater flows in two- and three-dimensional fracture networks. The results show that using the laminar flow equation in all fractures overestimates groundwater flowrates, while using the turbulent flow equation underestimates them.
ENGINEERING GEOLOGY
(2022)
Article
Mechanics
Eran Ben-Haim, Dotan Ilssar, Yizhar Or, Amir D. Gat
Summary: This study focuses on the viscous flow and elastic deformation in hyperelastic chambers, providing a closed-form expression for inflation dynamics and deriving the pressure distribution. The results are crucial for modeling the process of inflation and deflation.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Rohith Jayaram, Yucheng Jie, Lihao Zhao, Helge I. Andersson
Summary: Inertial spheroids are examined in a decaying Taylor-Green vortex flow, where their behaviors are influenced by particle clustering, preferential rotation, and alignment with local fluid vorticity. The clustering of spheroids peaks when the flow and particle time scales are similar. Low inertial spheroids are subjected to the centrifuging mechanism and reside in stronger strain-rate regions, while high inertial spheroids lag the flow evolution and sample strain-rate regions modestly. Contrary to expectations, spheroids reside in high strain-rate regions when particle and flow time scales are comparable due to dynamic interactions. Moderately inertial prolates preferentially spin and oblates tumble, correlating with parallel and perpendicular alignments with local fluid vorticity. However, for high inertial spheroids, preferential rotation and alignment are decorrelated due to a memory effect caused by continuously evolving flow scales.
Article
Physics, Fluids & Plasmas
Jie Yao, Fazle Hussain
Summary: The study reveals the impact of compressibility on drag control, showing that as the Mach number increases, the optimal sensing plane for maximum drag reduction shifts to larger values and a resonance buffer layer may be established, leading to a decrease in performance.
PHYSICAL REVIEW FLUIDS
(2021)
Review
Thermodynamics
Eric Loth
Summary: Turbulence is crucial for spreading particles and drops in energy systems, and recent advances have focused on the complexities of particle motion in turbulent flows. This review discusses the fundamental features of turbulence and its influence on particle motion, including turbulent diffusivity, kinetic energy of particle velocity, and turbophoresis. It also examines turbulent biases such as non-linear drag bias and clustering bias, as well as recent progress in turbulence modulation and particle collision frequency. A generalized flow regime is presented to summarize the interactions based on particle size and concentration.
PROGRESS IN ENERGY AND COMBUSTION SCIENCE
(2023)
Article
Engineering, Chemical
Ri Zhang, Shasha Zhang, Mengyan Ding
Summary: A thin liquid film method is proposed to evaluate sand erosion in annular flow. This method considers the direct interaction between the liquid film and gas core, as well as the entrainment and deposition of droplets. The erosion rate is calculated by considering the effects of liquid entrainment and particle velocity decay. The method is fully verified by comparing with experimental data.
Article
Engineering, Chemical
Yu Suo, Xianheng Su, Wenyuan He, Xiaofei Fu, Zhejun Pan
Summary: This research investigates the mechanical properties of sandstone-shale composite through orthogonal experimental method and discrete element simulation. The results show that different lithologies and thickness ratios can affect the strength and fracture mode of the composite rock samples.
Article
Engineering, Chemical
Maurizio Troiano, Andrea El Hassanin, Roberto Solimene, Alessia Teresa Silvestri, Fabrizio Scala, Antonino Squillace, Piero Salatino
Summary: This study investigates the potential of Fluidized Bed Finishing (FBF) for square flat AlSi10Mg specimens manufactured via Laser-Powder Bed Fusion (L-PBF) additive manufacturing technology. The results show that good finishing can be achieved using rotation-assisted tests, with a maximum reduction of surface roughness by 67%. Steel particles are found to be the most effective bed material.
Review
Engineering, Chemical
Ningbo Song, Wanzhong Yin, Jin Yao
Summary: Seawater's dissolved salts and minerals have various effects on the flotation process, including influencing the characteristics and behavior of flotation factors, as well as affecting the surface of sulfide minerals. In most cases, seawater has adverse effects on the flotation of sulfide minerals, but these effects can be mitigated by adjusting the reagents.
Article
Engineering, Chemical
Kaiqiao Wu, Shuxian Jiang, Victor Francia, Marc-Olivier Coppens
Summary: In rectangular and cylindrical annular fluidized beds, pulsating gas flow can create regular bubble patterns, overcoming challenges seen in conventional units. This study provides new opportunities for modularization of fluidized bed operations.
Article
Engineering, Chemical
Shuo Li, Huili Zhang, Jan Baeyens, Miao Yang, Zehao Li, Yimin Deng
Summary: The paper assesses the behavior of cohesive Geldart C-type particles when fluidized by air with the aid of vibration. It determines that mechanical vibration is a simple and effective method to improve the fluidity of cohesive particles during fluidization.
Article
Engineering, Chemical
Zhenfei Feng, Qingyuan Zhang, Shanpan Liang, Zhenzhou Li, Fangwen Guo, Jinxin Zhang, Ding Yuan
Summary: A new micro/mini-channel heat sink (MCHS) with a combined structure of longitudinal and transverse vortex generators is designed, using Al2O3 nanofluid as the working medium. The study explores the effects of transverse vortex generator shape and longitudinal vortex generator angle on the hydraulic and thermal characteristics, comprehensive performance, entropy generation, and exergy efficiency. The results show that the triangular transverse vortex generator improves the comprehensive performance and exergy efficiency. Combined with the longitudinal vortex generator, the MCHS achieves the best comprehensive performance, entropy generation, and exergy efficiency when the Reynolds number is 742.
Article
Engineering, Chemical
Kostas Giannis, Christoph Thon, Guoqing Yang, Arno Kwade, Carsten Schilde
Summary: This study presents a 3D convolutional neural network (3D-CNN) methodology for generating realistic 3D models of particles. The method trains on 2D projections of particle images to predict their 3D shapes, and evaluates the accuracy of the predictions using Fourier shape descriptors (FSDs). This methodology has wide applications in particle shape analysis.
Article
Engineering, Chemical
Zheng-qing Zhou, Lu-jia Chai, Yu-long Zhang, Ya-bin Wang, Ze-chen Du, Tian-yi Wang, Yu-zhe Liu
Summary: The dynamic oxidation and shell-breaking processes of aluminum nanoparticles (ANPs) during heating were studied using in situ transmission electron microscopy. The results revealed that the changes in shell thickness can be divided into three stages, and the active aluminum content of ANP decreased before shell-breaking.
Article
Engineering, Chemical
Fulei Chen, Huaqing Ma, Zihan Liu, Lianyong Zhou, Yongzhi Zhao
Summary: A particle breakage model based on the particle replacement scheme, using the polyhedral model to describe particles, is proposed in this work to accurately describe the breakage of a large number of particles. Additionally, a fast-cutting algorithm is proposed to reproduce the size distribution of progeny particles determined by the breakage model. The validation and simulation results show satisfactory accuracy, efficiency, and stability of the algorithm.
Review
Engineering, Chemical
Matteo Errigo, Christopher Windows-Yule, Massimiliano Materazzi, Dominik Werner, Paola Lettieri
Summary: Gas-solid fluidized-bed systems have advantages in terms of chemical reaction efficiency and temperature control, making them widely used in industrial applications. However, the design, scale-up, and optimization of these complex units are limited by the lack of deep physical understanding. Non-invasive and non-intrusive diagnostic techniques provide a way for researchers to study these systems without affecting the flow field or directly contacting the medium under study.
Article
Engineering, Chemical
Saeed Fateh, Mohammad Behshad Shafii, Mohammad Najafi, Cyrus Aghanajafi
Summary: Applying a magnetic field to ferrofluids alters their flow characteristics and enhances heat transfer. Through visualization and quantitative investigation, it is found that the magnetic field influences the flow patterns and velocity profiles, improving fluid mixing and vorticity magnitude.
Article
Engineering, Chemical
Lei Gao, Bingbing Wei, Xiaochuan Hu, Zaifeng Yao, Yiwen Fang, Xuejian Gao
Summary: In this study, a numerical model of sand triaxial test was established using discrete element software PFC3D, and an indoor triaxial test was conducted to calibrate the numerical model. The influence of microscopic parameters on the macroscopic mechanical response of sand was analyzed. The results showed that the friction coefficient had the greatest impact on the peak strength and residual strength of the sand's stress-strain curve, and it was positively correlated. The normal tangential stiffness ratio was negatively correlated, while the porosity and boundary flexibility stiffness had minimal influence on it.
Article
Engineering, Chemical
Xuan Liu, Jie Gong, Kai Jiang, Xiaojuan Lai, Yu Tian, Kang Zhang
Summary: This study aimed to improve the performance of lignite coal water slurries (CWSs) by synthesizing a series of three-arm amphiphilic block copolymers. By controlling the relative molecular weight, hydrophilic/hydrophobic ratio, and ionic group content, the apparent viscosity of CWSs was significantly reduced and the static stability was improved. Thermogravimetric testing and XPS analysis were conducted to reveal the mechanism behind the improved performance.
Article
Engineering, Chemical
Lanka Dinushke Weerasiri, Daniel Fabijanic, Subrat Das
Summary: Fluidization at low pressure offers significant benefits for the fine chemical industry. This study investigates the behavior of bubbles and bed expansion under low pressure conditions. It is found that lower pressure leads to larger bubbles, increased bubble quantity, and higher aspect ratio. The predictability is affected by the inhomogeneous fluidization, but low pressure fluidization can generate similar bubble sizes with lower fluidizing mass compared to atmospheric pressure.