Article
Mechanics
Aditi Sengupta, Prasannabalaji Sundaram, Vajjala K. Suman, Tapan K. Sengupta
Summary: Rayleigh-Taylor instability refers to the instability that occurs when the interface between two fluids of different densities is removed and the heavier fluid rests on top of the lighter fluid in the equilibrium state. This instability has been observed at various length scales, from nuclear fusion to astrophysical phenomena like supernova explosions. A non-overlapping parallel algorithm is used to simulate the three-dimensional Rayleigh-Taylor instability problem, providing insights into the vorticity creation and the dominance of viscous terms in the compressible flow.
Article
Engineering, Marine
Golnesa Karimi-Zindashti, Ozgur Kurc
Summary: This study examines the performance of an in-house code utilizing a deterministic vortex method on the rotation of circular and square cylinders. The results show that rotational motion reduces drag forces, suppresses fluctuating forces, and increases lift forces. The code accurately predicts vortex shedding suppression and identifies the emergence of near-field wakes in the flow over rotating square cylinders.
Article
Mechanics
Nilesh Kumar, Shashi Kumar, Venugopal Arumuru, Yogesh G. Bhumkar
Summary: This paper analyzes the effects of non-uniform laminar flow past a circular cylinder on the flow and sound fields. The study finds that the non-uniform inlet velocity profile alters the shed vortices and changes the characteristics of the sound field, with the jet-type inflow profile generating sound of higher frequency and intensity.
Article
Engineering, Marine
Jian Gu, Antonio Carlos Fernandes, Xiangxi Han, Xiaofeng Kuang, Wei Chen
Summary: In this article, numerical studies were conducted to investigate the effects of Reynolds number on vortex-induced vibration. The results showed that Reynolds number had more significant effects at moderate Reynolds numbers. The response amplitude was more sensitive to Reynolds number variations, while the frequency and hydrodynamic coefficients showed less variation. Additionally, the effectiveness of alpha in characterizing the correlation between Reynolds number and U* in different oscillatory systems was validated.
Article
Mechanics
Baiyang Song, Huan Ping, Hongbo Zhu, Dai Zhou, Yan Bao, Yong Cao, Zhaolong Han
Summary: In this study, the impact of incoming turbulence on the flow dynamics behind a single main cylinder was investigated using direct numerical simulations. The results showed that the incoming turbulence significantly affected the drag and lift coefficients and accelerated the turbulent transition of shear layers.
Article
Multidisciplinary Sciences
Kashif Ali, Anique Ahmad, Shahzad Ahmad, Sohail Ahmad, Wasim Jamshed
Summary: The paper develops a mathematical foundation for studying the complex interaction of Coriolis and Lorentz forces with the electromagnetohydrodynamic (EMHD) flow of a power-law fluid inside a microchannel with wall slip condition. The numerical results show a strong dependence of the power-law flow velocity on the Reynolds number and the Hartman number, and predict the existence of a cross-over point.
ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING
(2023)
Article
Mechanics
Bapuji Sahoo, Subharthi Sarkar, R. Sivakumar, T. V. S. Sekhar
Summary: Researchers have been exploring capturing the Taylor column phenomena numerically, facing challenges due to the complexity of the flow and inability of lower-order schemes. The Higher Order Compact Scheme is proposed to accurately capture the phenomena, with results aligning with experimental data. Physical analysis reveals the presence of reverse flow, cyclonic vortex, and geostrophic region under certain conditions.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2021)
Article
Engineering, Mechanical
Pooja Thakur, Naveen Tiwari, R. P. Chhabra
Summary: In this study, experiments were conducted to observe flow transitions of a rotating cylinder in shear-thinning fluids under different conditions, revealing critical values for Reynolds number, rotational velocity, and power-law index, as well as their nonmonotonic relationships. Additionally, it was found that increasing rotational velocity at a specific Reynolds number can suppress vortex formation in shear-thinning fluids, and the lift coefficient oscillates in unsteady flow regimes, with both amplitude and Strouhal number increasing with Reynolds number. The results highlight the complex interplay between kinematic and rheological parameters in non-Newtonian fluids at high Reynolds numbers, complementing existing low Reynolds number data.
JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME
(2021)
Article
Engineering, Aerospace
Lidia Caros, Oliver Buxton, Peter Vincent
Summary: Mars has lower atmospheric density and sound speed than Earth, making its rotor blades operate in a unique condition for helicopters. Optimizing the performance of unconventional airfoils under these conditions using traditional methods is limited. To overcome this limitation, high-order direct numerical simulations (DNSs) are used for aerodynamic shape optimization, resulting in improved lift and drag reduction. This study is the first to use DNSs for such optimization.
Article
Physics, Fluids & Plasmas
A. Ceci, S. Pirozzoli, J. Romero, M. Fatica, R. Verzicco, P. Orlandi
Summary: This paper is associated with a video that won the 2021 American Physical Society's Division of Fluid Dynamics Gallery of Fluid Motion Award. The video can be watched online at the Gallery of Fluid Motion website.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Engineering, Aerospace
Xiaobing Wang, Junqiang Wu, Jianzhong Chen, Yuping Li, Zhongliang Zhao, Guangyuan Liu, Yang Tao, Neng Xiong
Summary: A numerical study was conducted to investigate the influence of nonadiabatic wall effects on the aerodynamic characteristics of a standard model in cryogenic wind tunnels. The results showed that the change in wall temperature significantly affected the surface pressure distribution, transition position, and skin-friction coefficient of the model, resulting in variations in lift and drag coefficients of the aircraft. The study also examined the influences of wall temperature gradients on the flow characteristics of both laminar and turbulent boundary layers.
Article
Engineering, Multidisciplinary
Hassnia Hajji, Lioua Kolsi, Kaouther Ghachem, Chemseddine Maatki, Ahmed Kadhim Hussein, Mohamed Naceur Borjini
Summary: This study presents two and three-dimensional numerical simulations of flow through sudden expansion and contraction microchannels. Results show the appearance of a separate vortex in the corner after sudden expansion for low Reynolds numbers, with the vortex separation length increasing for high Reynolds numbers. The three-dimensional character of flow is more pronounced for higher Reynolds numbers.
ALEXANDRIA ENGINEERING JOURNAL
(2021)
Article
Thermodynamics
A. Shahid, H. L. Huang, C. M. Khalique, M. M. Bhatti
Summary: The study focuses on the incompressible steady flow with temperature-dependent viscosity of magnetohydrodynamics nanofluid through a vertically stretched porous sheet. The research employs the Reynolds exponential model and Darcy-Brinkman-Forchheimer model to formulate the mathematical modeling. The solutions of the looming nonlinear coupled differential equations are obtained numerically using the spectral local linearization method (SLLM), demonstrating stability and adaptability to solve nonlinear problems.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2021)
Article
Engineering, Marine
Tao Li, Shili Sun
Summary: Computational fluid dynamics (CFD) simulations were used to investigate the scale effect on the hydrodynamic performance of a single-blade cycloidal propeller. The study determined the hydrodynamic coefficients using the Shear Stress Transport (SST) turbulence model and a reasonable numerical scheme. The results showed that the scale effect of the cycloidal propeller differs from conventional screw propellers, leading to the invalidation of the scale effect formula recommended by the International Towing Tank Conference (ITTC). A new formula based on extensive numerical simulations was proposed.
Article
Mechanics
Chia-Lin Chiu, Chia-Ming Fan, Chia-Ren Chu
Summary: This study investigates the interaction between two free-falling spheres in water, verifies the predicted falling trajectories of the spheres, and explores the role of wake flows in the fluid-sphere interaction.
Article
Engineering, Chemical
Xinyang Li, Ming Jiang, Zheqing Huang, Qiang Zhou
Summary: This study investigates the drag force on oblate ellipsoids in random arrays using direct numerical simulations, considering factors such as Hermans orientation factor, mean crosswise sphericity, aspect ratio, and solid volume fraction. Two models are developed based on different orientation factors for accurate prediction of drag force and lateral force.
Article
Engineering, Chemical
Yaxiong Yu, Yu Li, Ming Jiang, Qiang Zhou
CHEMICAL ENGINEERING SCIENCE
(2020)
Article
Engineering, Chemical
Zheqing Huang, Lingxue Wang, Qiang Zhou
Summary: The study obtains the filtered reaction rate for coarse-grid simulations of reactive gas-solid flows through correcting its microscopic reaction rate, finding that the mean eta(Delta) is almost independent of reaction orders at the same Damkohler number. A closure correlation for the mean eta(Delta) is proposed, while a large standard deviation is observed. A presumed probability density function model is suggested to capture the fluctuating properties of eta(Delta), and the predictability of the closure correlations is evaluated through simulations in circulating fluidized beds of ozone decomposition.
Article
Energy & Fuels
Dongxu Zhang, Ting Min, Ming Jiang, Yaxiong Yu, Qiang Zhou
Summary: A model of a fluidized bed coupled with direct carbon solid oxide fuel cell was developed to investigate their coupling effects. The study found that factors such as CO2 inlet velocity and channel width would affect system performance, while the gasification rate of the anode is significantly influenced by the overlapping area between the anode surface and carbon activity.
Article
Engineering, Chemical
Yaxiong Yu, Yu Li, Xiao Chen, Fan Duan, Qiang Zhou
Summary: This study proposes two new coarsening strategies for the coarse-grained discrete element method (CGDEM) to more accurately predict granular temperature in simulations, particularly for homogeneous cooling systems (HCSs). These strategies also better reproduce time-averaged fields in bubbling fluidized beds compared to traditional strategies, highlighting the importance of considering both inelastic and frictional origins of energy dissipation in the coarsening strategy.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2021)
Article
Energy & Fuels
Tao Fu, Yun-Ting Tsai, Qiang Zhou
Summary: Computational fluid dynamics (CFD) was used to investigate the explosion characteristics of a Mg/air mixture in a 20 L apparatus. The simulation results showed that the best delayed ignition time was consistent with the experimental results, indicating a uniform dispersion of Mg particles in the apparatus under the effect of turbulence. The pressure development in the explosion system was divided into different stages, and the relative error between simulation and experiment was small.
Article
Chemistry, Physical
Yun-Ting Tsai, Tao Fu, Qiang Zhou
Summary: In the production of magnesium hydride, systematic experiments were conducted to study the explosion characteristics and suppression of hybrid Mg/H2 mixtures. It was found that certain explosion suppressants were effective, while others could actually stimulate the explosion by releasing flammable gases. This study provides valuable insights for reducing the risk in the H2 storage system of Mg.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Mechanics
Xiao Chen, Teng Ma, Qiang Zhou
Summary: This study resolves the sharp interface problem between dilute and dense phases in gas-solid flows through theoretical analysis and develops drag force models at the interface. The models show significantly improved performance compared to traditional models in numerical simulations.
Article
Engineering, Chemical
Yu Li, Sen Han, Yaxiong Yu, Xieyu He, Zheqing Huang, Qiang Zhou
Summary: The computational fluid dynamics-discrete element method is employed to simulate gas-solid flows with heat transfer. By adopting the strategy of repetitively resetting the gas phase temperature, the temperature difference between the gas and solid phases is effectively maintained. The study reveals that the traditional heat source method artificially enhances heat transfer in dense regions, hence a filtering approach is used to develop a more accurate model for the interphase heat transfer coefficient.
Article
Mechanics
Fan Duan, Yaxiong Yu, Xiao Chen, Qiang Zhou
Summary: Particle-resolved direct numerical simulations were used to investigate particle-particle drag force in bidisperse gas-particle suspensions. The relation derived by the kinetic theory of granular flow was found to overestimate the drag force due to the correlation between pre-collision velocities of colliding particles. It was observed that recently collided particle pairs are likely to collide again in a short time, leading to statistically smaller relative velocities before subsequent collisions. This study suggests that the drag force can be accurately predicted by considering the relative velocity within a local region near large particles.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Chemical
Xinyang Li, Xiao Chen, Bolun Yang, Qiang Zhou
Article
Engineering, Environmental
Xiao Chen, Yuxuan Zhao, Shaohua Du, Li Zhao, Qiang Zhou
Summary: Using particle-resolved direct numerical simulation, this study investigates the impact of Stefan flow on interphase heat transfer in flow past static random particle arrays. The results show that outward/inward Stefan flow thickens/thins the temperature boundary layer of particles, which hinders/improves the contact between main gas flow and particles. The positive Stefan Reynolds number (Resf) can cause a greater reduction in the Nusselt number compared to the maximum reduction in the drag coefficient under the same conditions. However, an increase in particle Reynolds number (Re) or solid volume fraction (c) can partially offset the impact of Stefan flow. A correction factor for interphase heat transfer considering the impact of Stefan flow is developed based on the simulation data for-3 < Resf < 6, 0 < Re < 100, and 0 < c < 0.5. It is important to note that the scalar chosen in this study is dimensionless temperature, but the results can be applied to any passive scalar.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Engineering, Chemical
Shaohua Du, Xiao Chen, Teng Ma, Lingxue Wang, Qiang Zhou
Summary: Sharp interfaces between dilute and dense phases are commonly observed in gas-solid fluidized beds. A microscale drag model that considers the interface influence is important for accurately predicting gas-solid dynamics. This study evaluated the performance of such a model using fine-grid two-fluid simulations and found that the interface drag model yields results closer to experimental data compared to the homogeneous drag law. The interface drag model also reduces the grid resolution requirement for simulating small particles in fine-grid two-fluid models.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2023)
Article
Mechanics
Ming Zhu, Jian Huang, Qiang Zhou, Zhaohui Yao
Summary: This paper improves the stability of the gas-liquid interface by using a three-dimensional-printed composite structure with transverse posts and reentrant structures in a microchannel. The length of the gas-liquid interface above the groove increases from micrometers to millimeters due to the effect of the transverse posts. The lattice Boltzmann method is applied to analyze the improved stability and explore the factors affecting the stability of the gas-liquid interface in this structure, providing a theoretical foundation for structural optimization.
Article
Mathematics, Applied
Zheqing Huang, Qi Huang, Yaxiong Yu, Yu Li, Qiang Zhou
Summary: This study numerically investigated flow and heat transfers in bidisperse gas-solid systems using CFD-DEM. Three different heat transfer models for bidisperse systems were compared. The results show that there are differences in particle mean temperature and temperature distribution among the three models at higher particle number ratios. However, when the particle number ratio is 1 and the particle diameter ratio is up to 4, the differences between the effects of heat transfer models are marginal.
