Article
Physics, Fluids & Plasmas
Steven T. Bramwell
Summary: This paper explores the possibility of establishing an analytic form of the distribution of the order parameter fluctuations in a two-dimensional critical spin-wave model or a two-dimensional Edwards-Wilkinson interface. The results show that the characteristic function of the distribution can be expressed exactly as a gamma function quotient, and a Charlier series using the convolution of two Gumbel distributions as the kernel converges to the exact result over a restricted domain. These findings can also be extended to calculate the temperature dependence of the distribution and provide insight into the origin of Gumbel-like distributions in non-extreme steady-state and equilibrium quantities.
Article
Physics, Multidisciplinary
Rayan Chatterjee, Navdeep Rana, R. Aditi Simha, Prasad Perlekar, Sriram Ramaswamy
Summary: In the study, it was found that an oriented collection of extensile swimmers must swim at a certain speed to escape the instability of viscous active suspensions. As the dimensionless combination R increases, the growth rate of instability slows down and the correlation length increases as the transition approaches.
Article
Astronomy & Astrophysics
Daniele Telloni, Raffaella D'Amicis, Roberto Bruno, Denise Perrone, Luca Sorriso-Valvo, Anil N. Raghav, Komal Choraghe
Summary: This study reveals the key role of Alfvenic fluctuations in modulating the recovery phase of geomagnetic storms, showing a high correlation between Alfvenic streams and concurrent recovery phases. It also provides opportunities for space weather predictions and crucial information for ground technologies and infrastructures affected by geomagnetic storms.
ASTROPHYSICAL JOURNAL
(2021)
Article
Physics, Fluids & Plasmas
Elise Almeras, Frederic Risso, Olivier Masbernat, Rodney O. Fox
Summary: This study experimentally investigates a liquid-solid fluidized bed involving inertial particles at a large Reynolds number. The flow dynamics exhibit three distinctive properties, which allow for the derivation of a model for the probability density functions of the velocity fluctuations. This model accurately describes experimental data and captures unique features such as skewness of fluctuations and symmetry between different volume fractions.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Mechanics
Mehedi H. Bappy, Pablo M. Carrica, Jiajia Li, J. Ezequiel Martin, Alberto Vela-Martin, Livia S. Freire, Gustavo C. Buscaglia
Summary: This paper presents a model for cavitation inception that takes into account the unresolved sub-grid scale (SGS) flow. By using direct numerical simulations (DNS), the pressure fluctuations, transport, and cavitating behavior in homogeneous isotropic turbulence (HIT) can be evaluated and used to create the model. The model predicts the inception pressure and cavitation rates accurately.
Article
Astronomy & Astrophysics
Tommaso Alberti, Davide Faranda, Reik Donner, Theophile Caby, Vincenzo Carbone, Giuseppe Consolini, Berengere Dubrulle, Sandro Vaienti
Summary: The study found that large-scale transitions in the solar wind magnetic field are induced by small-scale dynamics through an inverse cascade mechanism, while electron contributions may be hidden by instrumental noise.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Mechanics
Hanna Berning, Thomas Rosgen
Summary: This experimental study examines the stable flow structure of a fully turbulent von Karman swirling flow with counter-rotating disks using global and local characterization methods. The flow exhibits an azimuthal modulation in the central transverse plane, which is symmetric to the transverse plane. A low-order model consisting of three superimposed modes is used to illustrate the underlying flow topology. The dominant flow structure can be suppressed by pseudo-random reversal of the disk rotation, resulting in improved homogeneity and statistical stationarity.
Article
Physics, Multidisciplinary
Sukesh Roy, Joseph D. Miller, Gemunu H. Gunaratne
Summary: Studying turbulent flows is challenging due to the lack of high-frequency, high-resolution measurements. Using a burst-mode laser system in experiments can provide insights into small-scale structures and velocity dynamics in turbulent flows.
COMMUNICATIONS PHYSICS
(2021)
Article
Physics, Multidisciplinary
M. B. Christensen, T. Vibel, A. J. Hilliard, M. B. Kruk, K. Pawlowski, D. Hryniuk, K. Rzazewski, M. A. Kristensen, J. J. Arlt
Summary: Quantum systems exhibit inherent fluctuations in their physical observables, which presents challenges in studying interactions in quantum systems at finite temperature. This study characterizes atom number fluctuations in weakly interacting Bose-Einstein condensates, showing a reduction in fluctuations below canonical expectations. The experimental results set a benchmark for theoretical calculations under typical experimental conditions, revealing microcanonical nature of the system and a near linear scaling relationship between peak fluctuations and atom number.
PHYSICAL REVIEW LETTERS
(2021)
Article
Mechanics
A. De Leo, A. Stocchino
Summary: This study investigates the dispersion of heavy particles transported by sea waves using numerical simulations. It found that the interplay between wave Stokes drift and the inertial character of negatively buoyant particles results in an augmented settling velocity. The findings also indicate that the behavior of the particles significantly differs from that of the fluid even at very low Stokes numbers, making it rare to observe an asymptotic diffusive regime.
Article
Mechanics
J. Ocampo Jaimes, F. Graef, L. Zavala Sanson
Summary: In this study, the dispersion of particles in two-dimensional vortices, circular monopoles, and the Chaplygin-Lamb dipole was numerically investigated using a Lagrangian stochastic model. The results show that the dispersion behavior of particles varies depending on the flow patterns.
Article
Optics
Valeriy Kolosov, Victor Kulikov, Ernst Polnau
Summary: The power scintillations of a Gaussian laser beam propagated through a 7 km long atmospheric path were experimentally studied. The study analyzed the probability density function (PDF) and its properties under various scintillation conditions. The PDF was found to be described by the fractional exponential distribution in the strong scintillation regime and by the gamma distribution in the weak scintillation regime. The lognormal distribution was also observed for very weak scintillation conditions. The transition between distributions occurred at specific characteristic values of the aperture size and scintillation index.
Article
Astronomy & Astrophysics
Jens Kleimann, Sean Oughton, Horst Fichtner, Klaus Scherer
Summary: We propose a time-dependent, three-dimensional single-fluid model to study the transport of magnetohydrodynamic (MHD) turbulence in the outer heliosphere, which is evolving self-consistently with a dynamic large-scale solar wind. We focus on the region beyond the termination shock, where the solar wind expands subsonically, as well as sub-Alfvenically and nonradially. We refine the treatment of turbulence by considering a nonconstant energy difference and allowing each quantity its own characteristic correlation length scale.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
V David, S. Galtier, F. Sahraoui, L. Z. Hadid
Summary: In this study, a new method based on inertial dissipation is introduced to estimate the energy transfer rate in the solar wind. The presence of discontinuities near the Sun is found to lead to a strong energy transfer. Switchbacks exhibit a different scaling behavior compared to classical discontinuities.
ASTROPHYSICAL JOURNAL
(2022)
Article
Mechanics
Chang Hsin Chen
Summary: Linear interaction analysis is commonly used to analyze shock-turbulence interactions. By simplifying the complicated two-way interactions, linear analysis provides explicit solutions for post-shock turbulence. In this study, the analytical expressions are extended to pressure-dilatation and agree well with data when certain assumptions are met. Spatial evolutions under different flow conditions are presented, and the asymptotic states with increasing Mach number are discussed.
