Article
Mechanics
Xinran Zhao, Zongxin Yu, Jean-Baptiste Chapelier, Carlo Scalo
Summary: This paper investigates the pre- and post-reconnection dynamics of a trefoil knotted vortex, finding that the self-advection velocity before reconnection scales with inviscid parameters and reconnection occurs earlier and more rapidly at higher Reynolds numbers. The vortex propagation velocities after reconnection are affected by viscous effects, with the larger vortex ring carrying most of the helicity and enstrophy. The total helicity dissipation rate agrees reasonably well between large-eddy simulations and direct numerical simulations, with vortex centerline helicity and vortex-tube-integrated helicity being less sensitive to the reconnection process.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
G. A. M. van Kuik
Summary: This article introduces the significance of Prandtl's force field method in modern wind energy research and classifies and analyzes which type of body force field generates vorticity and converts energy. In addition, by re-deriving the Kutta-Joukowsky load and the relation between bound and trailing vorticity of a wing, it confirms the consistency between the force field method and the load output analysis method.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Farid Aligolzadeh, Markus Holzner, James R. Dawson
Summary: The interaction between small-scale vortical structures and the surrounding fluid is investigated using experimental and numerical data. The flow across the boundary of vortex structures is examined, and a non-Gaussian distribution of entrainment velocity is observed. The enstrophy transport equation is analyzed to quantify the inviscid and viscous components of the entrainment/detrainment process. The study also compares the findings with the Burgers vortex model.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mathematics, Applied
Qingshan Chen, Lili Ju, Roger Temam
Summary: This study proposes and evaluates a new energy and enstrophy conserving scheme for the shallow water equations. The results demonstrate its accuracy, conservation properties, and ability to simulate realistic energy and enstrophy spectra.
JOURNAL OF SCIENTIFIC COMPUTING
(2022)
Article
Computer Science, Interdisciplinary Applications
Raphael Comminal, Jon Spangenberg
Summary: This study introduces two unsplit geometric VOF schemes that extend a 2D cellwise conservative unsplit scheme to 3D, with innovative representation of streaksurfaces and advected liquid volumes computation. The 3D-CCU schemes demonstrated excellent performance in conserving liquid volume and maintaining physical boundedness of liquid volume fractions.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Mechanics
Dmitriy Zhigunov, Roman O. Grigoriev
Summary: This paper presents new classes of unstable recurrent solutions of the two-dimensional Euler equation with periodic boundary conditions. These solutions resemble the recurrent solutions of the Navier-Stokes equation, known as exact coherent structures. The Euler equation solutions come in infinite-dimensional continuous families, are connected to different types of solutions, and exhibit weak instability, leading to the frequent occurrence of these solutions in fully developed turbulence.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Alvaro Martinez-Sanchez, Esteban Lopez, Soledad Le Clainche, Adrian Lozano-Duran, Ankit Srivastava, Ricardo Vinuesa
Summary: The aim of this work is to analyze the formation mechanisms of large-scale coherent structures in the flow around a wall-mounted square cylinder and assess the causal relations between different flow modes. Conditional transfer entropy is used to identify the causal relations and understand the origins and evolution of different flow phenomena. The study reveals that vortex-breaker modes are the most causal modes, while no significant causal relationships were found for vortex-generator modes.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Geosciences, Multidisciplinary
S. B. Xu, S. Y. Huang, Z. G. Yuan, H. H. Wu, K. Jiang, J. Zhang
Summary: This study investigates intermittent structures and intermittent heating in Saturn's magnetosphere based on observations from the Cassini spacecraft. Positive correlations are found between electron temperature and magnetic field intermittency, as well as between turbulence heating rate and the probability density of intermittent structures. These results suggest that intermittent structures contribute to turbulent heating in Saturn's magnetosphere.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Mechanics
Praveen Kumar, P. Nandal, R. Uma, R. P. Sharma
Summary: This article presents a numerical model to study wave turbulence in fluids and investigates the localized structures of nonlinear waves and turbulence generation using numerical simulation and semi-analytical methods. The results show that turbulence can break periodic patterns and the turbulent power spectrum follows a specific scaling law.
Article
Mechanics
L. Djenidi, R. A. Antonia, S. L. Tang
Summary: In the theory of fluid turbulence, mathematical constraints regarding longitudinal velocity increment moments and scaling exponents can be obtained using Holder's inequality and the Cauchy-Schwarz inequality. These results should guide the development of new theoretical and modeling approaches to ensure they are consistent with the constraints imposed by Holder's inequality.
Article
Mechanics
Stergios Katsanoulis, Florian Kogelbauer, Roshan Kaundinya, Jesse Ault, George Haller
Summary: Instantaneous features of three-dimensional velocity fields can be visualized most directly through streamsurfaces, but it is often unclear which streamsurfaces to choose given the infinite possibilities passing through each point. However, vector fields with a non-degenerate first integral can define a continuous family of streamsurfaces, while vortical regions in generic vector fields may have local first integrals over a discrete set of streamtubes. In this study, a method is introduced to construct such first integrals from velocity data and it is shown that their level sets accurately frame vortical features in known examples.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Weiyu Shen, Jie Yao, Fazle Hussain, Yue Yang
Summary: In this study, a new method for quantifying twist in viscous flows is proposed, which allows for the characterization of coiling vortex lines and internal structures within a vortex. This method is important for understanding laminar-turbulence transition, vortex instability, reconnection, and breakdown.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mathematics, Applied
Wanying Mao, Qifeng Zhang, Dinghua Xu, Yinghong Xu
Summary: In this paper, we derive, analyze, and extensively test fourth-order compact difference schemes for the Rosenau equations in one and two dimensions. These schemes are applied under spatial periodic boundary conditions using the double reduction order method and bilinear compact operator. Our results show that these schemes satisfy mass and energy conservation laws and have unique solvability, unconditional convergence, and stability. The convergence order is four in space and two in time under the D infinity-norm. Several numerical examples are provided to support the theoretical findings.
APPLIED NUMERICAL MATHEMATICS
(2024)
Article
Materials Science, Multidisciplinary
Jingkui Yang, Tuanhui Jiang, Bujin Liu, Chun Zhang, Xiangbu Zeng, Li He, Wei Gong
Summary: This study investigated the bubble nucleation of polymer foams using nucleation theory and established a mathematical model based on in-situ observations and measurements. The effects of different factors on bubble nucleation were studied in experiments, leading to the development of a new mathematical model. The model can intuitively characterize the process of foaming nucleation and has potential applications in other nucleation processes.
MATERIALS & DESIGN
(2021)
Article
Mechanics
Nikolas Olson Aksamit
Summary: We introduce a mapping method that quantifies and visualizes the full geometry of three-dimensional deformation in fluid flows using Cauchy-Green strain tensor eigenvalues. The mapping system visualizes the role of all three eigenvalues in a single plot, providing a comprehensive understanding of the fluid deformation. We also provide methods to visualize the degree of approximation of limiting deformation states and tools to quantify differences between flows based on the compositional geometry of invariant manifolds.
JOURNAL OF FLUID MECHANICS
(2023)
