Article
Mathematics, Applied
I. R. Sataev, N. V. Stankevich
Summary: We study the hyperchaos formation scenario in the modified Anishchenko-Astakhov generator, which is connected with the existence of secondary torus bifurcations and the birth of saddle-focus cycles hierarchy. The hyperchaos emerges from an inverse bifurcation cascade accompanied by absorbing cycles from this hierarchy.
Article
Mechanics
Zhi Deng, Wen-Li Chen, Zifeng Yang
Summary: Inspired by the owl's silent flight, researchers experimentally investigated the flow control mechanism of soft trailing fringes (STFs) on the wake of the S833 airfoil. The results showed that the STFs significantly suppressed turbulent quantities, modified vortical structures, and mitigated wall-pressure peaks in the airfoil wake. However, the control effect of the STFs was limited at median angles of attack.
Article
Mathematics, Applied
Feng Liu, Hantao Liu, Hongkai Zhao, Pengfei Lyu
Summary: The inverse energy cascade in homogeneous isotropic turbulence is described using an eigenvalue method, quantitatively capturing the backward energy transfer process and applicable to both isotropic turbulence and resolved velocity fields. This method, based on the product of eigenvalues of the rate-of-strain tensor, is easier to obtain compared to traditional velocity derivative skewness S-k, and has potential for extension to anisotropic turbulence. The presented description aims to inspire future research on modeling the backward energy transfer process and improve the accurate prediction of complex flows.
APPLIED MATHEMATICS AND MECHANICS-ENGLISH EDITION
(2021)
Article
Chemistry, Multidisciplinary
Yongbo Shui, Hansheng Wen, Jian Zhao, Yudong Wu, Haibo Huang
Summary: This paper provides an overview of the optimization design process for a multi-objective, two-level engineering problem using the generalized inverse cascade method under uncertainty. The primary goal is to improve the vibration isolation performance of a mounting system, considering uncertain factors affecting its stiffness. The study focuses on determining the value range of design variables at the bottom layer to meet the design goal with a specified confidence level. The methodology is demonstrated through the optimization design of a powertrain mount, using a data-driven approach and an intelligent optimization algorithm.
APPLIED SCIENCES-BASEL
(2023)
Article
Engineering, Aerospace
Martin Buszyk, Cyril Polacsek, Thomas Le Garrec, Raphael Barrier, Christophe Bailly
Summary: This work focuses on innovative stator designs to reduce noise in aeroengines. The accurate prediction of noise radiation from passive treatments, such as leading-edge serrations, requires studying turbulent structure definition. The study proposes a modified Fourier modes-based methodology to obtain a three-dimensional turbulence field and evaluates the noise reduction and aerodynamic performance.
Article
Engineering, Aerospace
Yinxin Zhu, Zhenbing Luo, Wenqiang Peng, Qiang Liu, Yan Zhou, Wei Xie, Pan Cheng, Zhengxue Ma, Xuzhen Xie
Summary: This study proposes a shock wave control method based on air jets to effectively reduce shock wave loss at the trailing edge of a supersonic cascade. Computational methods were used to analyze the flow control mechanism and parameter effects. The results show that the method can improve the flow condition and weaken the strength of the trailing-edge shock, thereby reducing the total pressure loss.
Article
Materials Science, Multidisciplinary
Liang-Jun Zhai, Guang-Yao Huang, Shuai Yin
Summary: In this paper, we investigate the driven dynamics of the localization transition in the non-Hermitian Aubry-Andre model with the periodic boundary condition. We determine the critical exponents for various characteristics such as the localization length, energy gap, and inverse participation ratio. We also show that the driven dynamics across the critical point can be described by the Kibble-Zurek scaling and this scaling can be generalized to the localization phase transitions in the excited states.
Article
Thermodynamics
Shota Moriguchi, Hironori Miyazawa, Takashi Furusawa, Satoru Yamamoto
Summary: This study investigates the effects of trailing edge cutback on the turbulent flow field and aerodynamic loss of a turbine blade using Large-Eddy-Simulation (LES). The results show that the cutback alters the boundary layer thickness and base pressure, leading to increased aerodynamic loss. Additionally, the analysis of time-dependent flow dynamics and phase-locked flow field reveals the flow dynamics responsible for pressure fluctuations.
Article
Geosciences, Multidisciplinary
Xin Shao, Ning Zhang, Jie Tang
Summary: The observed inverse energy cascade in typhoon boundary layers originates from the rapid rotation of typhoons. The transition from the direct energy cascade regime to the inverse energy cascade regime can be characterized by the Zeman length scale. The ratio of the inverse energy cascade flux to the direct energy cascade flux is controlled by the turbulence Rossby number.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Physics, Fluids & Plasmas
Keisuke Fujii
Summary: Nonthermal velocity distributions with much greater tails than a Maxwellian have been observed for radical atoms in plasmas for a long time. Historically, such velocity distributions have been modeled by a two-temperature Maxwell distribution. In this paper, the author proposes a model based on collisional energy cascade, which is compared with molecular dynamics simulations and experimentally observed velocity distributions.
Article
Computer Science, Information Systems
Chen-Kun Tsung, Fa-Shian Chang, Xiu-Yu Liu
Summary: A proposed edge-based monitoring system (EMS) reduces communication costs and decision-making delay by moving data examination to end vehicles. It has been successfully implemented to monitor AGV and unmanned aerial vehicles, showing good results in examining abnormal events.
Article
Computer Science, Theory & Methods
Pedro Cruz, Nadjib Achir, Aline Carneiro Viana
Summary: Multi-Access Edge Computing (MEC) attracts attention due to its implications in science, technology, and commerce. However, existing MEC initiatives are incomplete, and understanding experimental prototypes and implementations is crucial. This study discusses and surveys existing MEC projects, comparing strategies, limitations, and tools while addressing unresolved issues in practice.
ACM COMPUTING SURVEYS
(2023)
Article
Computer Science, Artificial Intelligence
Jianzhong He, Shiliang Zhang, Ming Yang, Yanhu Shan, Tiejun Huang
Summary: In this paper, a bi-directional cascade network (BDCN) architecture is proposed for edge detection at different scales. The network is supervised at specific scales and utilizes a scale enhancement module (SEM) to generate multi-scale features. The proposed method encourages the learning of multi-scale representations and achieves improved performance in edge detection and other vision tasks.
IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE
(2022)
Article
Physics, Fluids & Plasmas
George Sofiadis, Ioannis E. Sarris, Alexandros Alexakis
Summary: We show that the inverse cascade of two-dimensional turbulence can exhibit a lack of self-similarity and intermittency when the energy injection is constrained within a fractal set of dimension less than two. Numerical simulations of two-dimensional turbulence with different forcing functions and fractal dimensions are conducted, demonstrating the loss of self-similarity and the emergence of intermittency as the fractal dimension decreases. This model serves as a valuable example to understand and test multifractal models of turbulence.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Chemistry, Multidisciplinary
Jie Feng, Buchen Wu, Shujin Laima
Summary: The study investigates the effects of trailing-edge reattachment on flutter stability by adjusting the vortex reattachment through different trailing edge designs. Changing the trailing edge design can increase flutter stability and lower the likelihood of limit cycle flutter occurrence.
APPLIED SCIENCES-BASEL
(2021)
Article
Mechanics
Takahiro Nemoto, Alexandros Alexakis
Summary: The study reveals that the decay time scale of turbulence in pipe flows increases double-exponentially as Reynolds number approaches its critical value, influenced by the transition between stable turbulence and metastable states.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Fluids & Plasmas
Alexandros Alexakis, Francois Petrelis, Santiago J. Benavides, Kannabiran Seshasayanan
Summary: This study investigates symmetry breaking in a turbulent environment, showcasing the transition from a symmetric state to a symmetry-breaking state through two examples. The critical behavior of these transitions is shown to be related to the multiplicative nature of fluctuations and can be predicted in certain limits using results from statistical properties of random interfaces. The results suggest the existence of a new class of out-of-equilibrium phase transitions controlled by multiplicative noise.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Geosciences, Multidisciplinary
Santiago J. Benavides, Eric Deal, Matthew Rushlow, Jeremy G. Venditti, Qiong Zhang, Ken Kamrin, J. Taylor Perron
Summary: The study discusses how sediment transport near the threshold of grain motion is influenced by rare transport events, making it difficult to calibrate sediment transport laws and define a clear threshold for grain entrainment. The research presents a model to capture this intermittency and utilize noisy statistics of sediment transport to predict the sediment entrainment threshold and fluid stress variations. The findings suggest strategies for improving measurements and predictions of sediment flux and hint at potential changes in the sediment transport law near the threshold of motion.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Mechanics
Santiago J. Benavides, Keaton J. Burns, Basile Gallet, James Y-K. Cho, Glenn R. Flierl
Summary: The study numerically investigates three-dimensional magnetohydrodynamic turbulence affected by the competing effects of rotation and a background magnetic field. It finds that increasing the rotation rate leads to significant changes in the turbulent flow structure in the presence of a strong background field, and identifies distinct values where the transitions occur.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Adrian van Kan, Alexandros Alexakis
Summary: This study investigates forced, rapidly rotating and stably stratified turbulence using an asymptotic expansion method, focusing on a region that is difficult to attain through direct numerical simulations. The study reveals the occurrence of forward and split energy cascades in this region, and presents theoretical arguments supporting the observed energy cascade phenomena.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Xander M. de Wit, Adrian van Kan, Alexandros Alexakis
Summary: In this study, direct numerical simulations of thin-layer flow were used to investigate whether the bistable range survives as the domain size and turbulence intensity are increased. The research found that the bistable range grows as the box size and/or Reynolds number Re are increased.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Geosciences, Multidisciplinary
Qiong Zhang, Eric Deal, J. Taylor Perron, Jeremy G. Venditti, Santiago J. Benavides, Matthew Rushlow, Ken Kamrin
Summary: Bedload sediment transport plays a crucial role in shaping landscapes, but the relationship between sediment flux and driving factors is not well understood. In this study, the researchers experimentally validated a numerical scheme and explored the parameter space controlling sediment transport. The results showed that the dimensionless transport rate is not influenced by several factors for gentle slopes at a medium to high fixed Shields number. The study also highlighted the significance of fluid torque near the threshold in sediment transport.
JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE
(2022)
Article
Astronomy & Astrophysics
Santiago J. Benavides, Keaton J. Burns, Basile Gallet, Glenn R. Flierl
Summary: The study shows that when considering the Lorentz force, the drag parameterization fails as the timescale associated with it becomes shorter, but the effective drag coefficient remains stable afterwards. By considering the asymptotic limit of low conductivity and strong magnetic field, the drag parameterization can be improved for future numerical models of hot Jupiter atmospheric circulation.
ASTROPHYSICAL JOURNAL
(2022)
Article
Physics, Fluids & Plasmas
Alexandros Alexakis, Sergio Chibbaro
Summary: In this study, the statistical properties of the local energy flux rate towards small scales in three isotropic turbulent magnetohydrodynamic flows with different magnetic field strengths and structures were examined using highly resolved direct numerical simulations. The results showed that the probability distribution of the local energy flux exhibited long tails related to extreme events, similar to the hydrodynamic case. The different terms of the energy flux displayed different properties and showed sensitivity to the type of flow examined. Furthermore, a correlation was observed between the local energy flux and the gradients of the involved fields, with a stronger dispersion than in hydrodynamic flows. Additionally, the local energy flux was found to depend on the local amplitude of the magnetic field to some extent.
JOURNAL OF PLASMA PHYSICS
(2022)
Article
Multidisciplinary Sciences
Eric Deal, Jeremy G. Venditti, Santiago J. Benavides, Ryan Bradley, Qiong Zhang, Ken Kamrin, J. Taylor Perron
Summary: Bed load sediment transport is a critically important mechanism in various contexts, but predictions of sediment flux are often imprecise. While many studies have focused on grain size variability as a source of uncertainty, the role of grain shape, which can influence transport rates, has been less investigated. This study shows that grain shape can significantly modify bed load transport rates, and proposes a shape-corrected sediment transport law. The findings improve predictions of sediment transport and reconcile theories developed for spherical particles with natural sediment grains.
Article
Physics, Multidisciplinary
Guillaume Bermudez, Alexandros Alexakis
Summary: The presence of large scale magnetic fields in nature is often attributed to the inverse cascade of magnetic helicity driven by turbulent helical dynamos. In this study, the authors show that the inverse flux of magnetic helicity toward the large scales is bounded by a certain constant and decreases with the magnetic Reynolds number. Numerical simulations demonstrate that the nonlinear saturation is achieved by a balance between the inverse cascade and dissipation, with the saturation value of the magnetic energy determined by the domain size scales, magnetic Reynolds number, and magnetic Prandtl number. These findings have critical implications for the modeling of astrophysical dynamos.
PHYSICAL REVIEW LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Santiago J. Benavides, Eric Deal, Jeremy G. Venditti, Ryan Bradley, Qiong Zhang, Ken Kamrin, J. Taylor Perron
Summary: Near the threshold of grain motion, sediment transport is intermittent, with rare bursts and long periods of low transport. The origin of intermittency is found in the velocity distributions of rolling grains, rather than the activity of grains. Incorporating this type of intermittency into sediment transport models can lead to improved predictions of sediment flux.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Environmental Sciences
Ben Ajzner, Alexandros Alexakis
Summary: This study examines a turbulence shell model to investigate the probability distributions of velocity modes with changing scales. It demonstrates that while velocity amplitudes are not scale-invariant, their ratios are. Furthermore, the study shows how the probability distributions of velocity modes can be re-scaled to present a scale-independent form using large deviation theory.
Article
Physics, Fluids & Plasmas
Adrian van Kan, Alexandros Alexakis, Marc-Etienne Brachet
Summary: The paper proposes a simple, energy-conserving model to describe the three-dimensional instabilities growing on two-dimensional flows and studies the evolution of the model in different stages. It identifies specific growth patterns and nonlinear phenomena, which are important for understanding and analyzing DNS results and guiding further theoretical developments.
