Article
Physics, Multidisciplinary
Adam Griffin, Giorgio Krstulovic, Victor S. L'vov, Sergey Nazarenko
Summary: We present an exact unique constant-flux power-law analytical solution for the wave kinetic equation, applicable for ak << 1. Our theory describes acoustic turbulence in 2D Bose-Einstein condensates, and the corresponding spectrum is confirmed through numerical simulations.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mechanics
Brodie C. Pearson, Jenna L. Pearson, Baylor Fox-Kemper
Summary: The study proposes new relations to diagnose energy and enstrophy dissipation rates in anisotropic two-dimensional turbulence, using second-order advective structure functions. These new relations show improvement over existing methods through increased accuracy, insensitivity to sampling direction, and lower temporal and spatial variability. Advective structure functions have benefits under weakly anisotropic conditions, becoming increasingly important as third-order structure functions become inappropriate.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Martin Jacques-Coper, Valentina Ortiz-Guzman, Jorge Zanelli
Summary: This study presents a simplified model of the terrestrial planet atmosphere, describing it as a two-dimensional open system with an ideal gas. The model considers the effects of radiation, matter exchange, diffusion, and dissipation. The dynamics of the atmosphere is governed by non-linear differential equations, and the problem can be solved analytically or numerically depending on the level of non-linearity. The study provides analytical expressions and simulations for the linear regime, allowing exploration of the model's response to parameter changes. Interestingly, a 2.5% reduction in emissivity can lead to a 7-degree Celsius increase in average global temperature.
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
Oceanography
Yu-Kun Qian, Shiqiu Peng, Xixi Wen, Tongya Liu
Summary: This study proposes two new diffusivity diagnostics, local Lagrangian diffusivity and local effective diffusivity, to quantify localized, instantaneous, irreversible mixing. These diagnostics can help explore the interrelations among different mixing models and minimize discrepancies between different estimates.
JOURNAL OF PHYSICAL OCEANOGRAPHY
(2022)
Article
Physics, Multidisciplinary
Xiaoyu Xuan, Wanlin Guo, Zhuhua Zhang
Summary: This study identifies 65 monolayers exhibiting in-plane ferroelasticity using high-throughput computation and first-principles calculations. The molecular orbital theory analysis reveals that ferroelastic distortion arises when both M-d/X-p and M-d/M-d couplings are weak. The research team has developed a one-dimensional descriptor that accurately predicts the difference between ferroelastics and nonferroelastics. Furthermore, they have found 11 compounds that exhibit both ferroelasticity and magnetism, raising the prospects of developing 2D ferroelasticity-based multiferroics.
PHYSICAL REVIEW LETTERS
(2022)
Article
Mechanics
Jin-Han Xie, Shi-Di Huang
Summary: Through simulations of an idealized isotropic convection system, we provide evidence for the existence of Bolgiano-Obukhov (BO) scaling in Rayleigh-Benard convection (RBC) and establish its association with the inverse kinetic energy cascade. We also observe strong intermittent effects in the buoyancy field, but not in the velocity.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Erik Lindborg, Arne Nordmark
Summary: This study conducts a spectral analysis of a non-divergent flow on a sphere based on Fjortoft's method. It demonstrates that the spherical harmonic energy spectrum remains invariant under rotations of the polar axis, and derives the spectral energy equation and energy transfer relations. The importance of exploring two-dimensional turbulence through simulations using spherical geometry is highlighted, based on the explanation of relevant theories and hypotheses.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Materials Science, Multidisciplinary
L. Krauss-Kodytek, W. -R. Hannes, T. Meier, C. Ruppert, M. Betz
Summary: The study investigates the nondegenerate two-photon absorption coefficient beta(omega(1), omega(2)) in the semiconductor ZnSe, showing a substantial increase in absorption strength with higher omega(1)/omega(2) ratio. Different crystallographic orientations and polarization configurations are considered, with theoretical analysis aligning well with experimental results.
Article
Mechanics
Nikolay A. Ivchenko, Sergey S. Vergeles
Summary: The study focuses on time-averaged properties of coherent vortices in two-dimensional turbulence, classifying weak perturbations as waves of condensate propagating in the radial direction. The dispersion law and propagation length of these waves are dependent on the radial position inside the vortex flow, with variations between saturated condensate and viscous condensate cases.
Article
Physics, Fluids & Plasmas
Seunghwan Shin, Filippo Coletti, Nicholas Conlin
Summary: In this study, forced two-dimensional turbulence in electromagnetic layers of fluids was investigated across a wide range of Reynolds numbers and Reynolds numbers with friction coefficients. Various observables characterizing turbulence development showed that all descriptors collapse on master curves against Reynolds number with friction coefficients, providing a criterion for fully developed turbulence in this class of flows. Additionally, a scaling relation was proposed to relate the amount of energy going to the large scales to the forcing scale-to-layer thickness ratio.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Mechanics
Aditya G. G. Nair, James Hanna, Matteo Aureli
Summary: In two-dimensional decaying homogeneous isotropic turbulence, kinetic energy and enstrophy are transferred to larger and smaller scales, respectively. It is challenging to identify the important flow structures that govern this behavior in such complex dynamics. Two flow-modification strategies are proposed and implemented, leveraging the inviscid global conservation of energy and enstrophy to selectively and simultaneously change these quantities and guide the system towards steady-state or late-stage behavior. One strategy is based on local flow field information, while the other is global. Various flow structures excited by these modified inputs are observed and compared with recent literature. Energy modification excites smaller wavenumber structures in the flow, while enstrophy modification differs.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Vilda K. Markeviciute, Rich R. Kerswell
Summary: By conducting direct numerical simulations of two-dimensional channel flow with fixed volume flux for Reynolds numbers, it was found that there exist asymmetric turbulent states with heightened turbulent behavior near one of the channel walls and with a significant reduction in pressure gradient compared to symmetric counterparts. The symmetric solution becomes unstable at a critical point, leaving only the asymmetric state and its reflected counterpart as attractors, which eventually become connected to apparently random and infrequent wall switches. The symmetry of the flow is eventually restored after averaging over extremely long times.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Physics, Multidisciplinary
Kaveh Khaliji, Luis Martin-Moreno, Phaedon Avouris, Sang-Hyun Oh, Tony Low
Summary: The ability to control light polarization state is crucial for various applications. This study proposes the use of a stack of anisotropic van der Waals materials to create optical elements with different characteristics. The twisted stack with electrostatic control can function as arbitrary-birefringent wave-plate or polarizer, enabling the access to a wide range of polarization transformers. An electrostatic-reconfigurable stack is also discussed, which can operate as four different polarizers for Stokes polarimetry.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Multidisciplinary
Xiang -Pei Liu, Xing-Can Yao, Xiaopeng Li, Yu-Xuan Wang, Chun-Jiong Huang, Youjin Deng, Yu-Ao Chen, Jian-Wei Pan
Summary: We systematically studied the decay of quasi-two-dimensional vortices in an oblate strongly interacting Fermi gas. We observed that as the system temperature decreases, the lifetime of the vortices increases in the BEC regime but decreases at unitarity and in the BCS regime. These observations can be qualitatively explained by a phenomenological model involving diffusion and two-body collisional loss, where the vortex lifetime is mainly determined by the slower process. The counterintuitive vortex decay in the BCS regime can be interpreted by considering the competition between the temperature dependence of the vortex annihilation rate and that of unpaired fermions. Our findings suggest a competing mechanism for the complex vortex decay dynamics in the BCS-BEC crossover for fermionic superfluids.
PHYSICAL REVIEW LETTERS
(2022)
Article
Multidisciplinary Sciences
Jean-Baptiste Gorce, Konstantin Y. Bliokh, Hua Xia, Nicolas Francois, Horst Punzmann, Michael Shats
Summary: This study reports self-guided propulsion of fast-spinning magnetic particles on a liquid surface, forming composite spinner-vortex quasiparticles with nontrivial dynamics. These spinner-vortices are attracted and dynamically trapped near boundaries, propagating along any shaped wall like liquid wheels. The propulsion velocity and distance to the wall are controlled by the spinner's angular velocity through balance between forces.
Article
Physics, Fluids & Plasmas
J. H. E. Proll, G. G. Plunk, B. J. Faber, T. Gorler, P. Helander, I. J. McKinney, M. J. Pueschel, H. M. Smith, P. Xanthopoulos
Summary: In fusion devices, the geometry of the confining magnetic field plays a crucial role in the instabilities that cause turbulent heat loss. A study on the Wendelstein 7-X experiment shows that optimizing its magnetic field configuration can not only reduce the transport driven by trapped electron modes, but also mitigate the ion-temperature-gradient modes as long as an electron density gradient exists. This finding provides theoretical support for the existence of enhanced confinement regimes in the presence of strong density gradients.
JOURNAL OF PLASMA PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
C. C. Hegna, D. T. Anderson, A. Bader, T. A. Bechtel, A. Bhattacharjee, M. Cole, M. Drevlak, J. M. Duff, B. J. Faber, S. R. Hudson, M. Kotschenreuther, T. G. Kruger, M. Landreman, I. J. McKinney, E. Paul, M. J. Pueschel, J. S. Schmitt, P. W. Terry, A. S. Ware, M. Zarnstorff, C. Zhu
Summary: This article reports recent advances in theoretical and computational plasma physics for improving the stellarator concept. These advances include improved energetic ion confinement, impact of three-dimensional shaping on turbulent transport, reducing coil complexity, novel optimization and design methods, and computational magnetohydrodynamic tools. These advancements enable the development of new stellarator configurations with improved confinement properties.
Article
Physics, Multidisciplinary
M. Davoodianidalik, H. Punzmann, H. Kellay, H. Xia, M. Shats, N. Francois
Summary: This study provides experimental evidence for the existence of fluctuation-induced forces mediated by turbulent fluctuations in confined turbulence. The strength of this long-range interaction is dependent on the wall separation and energy injection rate in the turbulent flow. The mechanism of force generation is rooted in the nontrivial fluid-wall coupling, where coherent flow structures are guided by the cavity walls.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Fluids & Plasmas
J. M. Duff, B. J. Faber, C. C. Hegna, M. J. Pueschel, P. W. Terry
Summary: The study investigated the effects of triangularity on the linear and nonlinear properties of ion-temperature-gradient-driven turbulence. It was found that triangularity significantly influences the linear growth rates and nonlinear heat flux, with negative delta suppressing zonal modes and positive delta enhancing zonal flows.
PHYSICS OF PLASMAS
(2022)
Article
Multidisciplinary Sciences
Konstantin Y. Bliokh, Horst Punzmann, Hua Xia, Franco Nori, Michael Shats
Summary: This article introduces the fundamental concepts of spin and momentum in quantum particles or fields, and their specific manifestations in wave fields. It demonstrates, through experiments, the natural generation of the Belinfante-Rosenfeld construction in gravity waves and explores the universality of these concepts and the significance of a new research platform.
Article
Physics, Fluids & Plasmas
Alexandra LeViness, John C. C. Schmitt, Samuel A. A. Lazerson, Aaron Bader, Benjamin J. J. Faber, Kenneth C. C. Hammond, David A. A. Gates
Summary: The goal of this work was to optimize stellarator equilibrium for good confinement of energetic particles. This was achieved by minimizing deviations from quasi-axisymmetry and reducing the angle between magnetic flux surfaces and contours of the second adiabatic invariant. Multiple optimizations resulted in equilibria with significantly reduced energetic particle losses, as evaluated by Monte Carlo simulations.
Article
Chemistry, Physical
F. M. Schaller, H. Punzmann, G. E. Schroeder-Turk, M. Saadatfar
Summary: This paper explains the observations of a study on the X-ray computed tomography of granular ellipsoidal packings using a fundamental theoretical relationship for mixture distributions. The main finding is that the bi-disperse ellipsoidal packings studied can be interpreted as a mixture of two uncorrelated mono-disperse packings, insensitive to the compaction protocol.
Article
Physics, Fluids & Plasmas
M. J. Gerard, B. Geiger, M. J. Pueschel, A. Bader, C. C. Hegna, B. J. Faber, P. W. Terry, S. T. A. Kumar, J. C. Schmitt
Summary: The optimization of helically symmetric experiment (HSX) for reduced microinstability has been achieved by examining a large set of configurations within a neighborhood of the standard operating configuration. A database of over 10^6 magnetic-field configurations for HSX was generated by varying the currents in external coils, and this database helped to identify a set of configurations that can regulate trapped-electron-mode stability in HSX. These results demonstrate the sensitivity of plasma behavior to changes in a 3D magnetic field and the potential for turbulence optimization in HSX.
Article
Physics, Fluids & Plasmas
Mahdi Davoodianidalik, Hamid Kellay, Nicolas Francois
Summary: This study reveals the emergence of a fluctuation-induced force observed in wave-driven turbulence, which is influenced by the energy and anisotropy of the wave motion. The results contribute to the research on aggregation processes in the presence of turbulence and the accumulation of plastic debris in coastal marine ecosystems, as well as the modeling of planetary formation.
