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The evolution of large-scale magnetic fields in disk galaxies is investigated numerically. The gasdynamical simulations in a disk perturbed by spiral or bar potential are incorporated into the kinematic calculations of induction equations…

Astrophysics · Physics 2007-05-23 K. Otmianowska-Mazur , M. Chiba

We report numerical simulations on granular shear flows confined between two flat but frictional sidewalls. Novel regimes differing by their strain localization features are observed. They originate from the competition between dissipation…

Soft Condensed Matter · Physics 2015-10-28 Riccardo Artoni , Patrick Richard

The boundary-induced scaling of three-dimensional random field Ising magnets is investigated close to the bulk critical point by exact combinatorial optimization methods. We measure several exponents describing surface criticality:…

Disordered Systems and Neural Networks · Physics 2009-11-11 L. Laurson , M. J. Alava

A key question in understanding the observed magnetic field topologies of cool stars is the link between the small- and the large-scale magnetic field and the influence of the stellar parameters on the magnetic field topology. We examine…

Solar and Stellar Astrophysics · Physics 2018-05-23 L. T. Lehmann , M. M. Jardine , D. H. Mackay , A. A. Vidotto

The axisymmetric 3-D MHD outflow of a cold plasma from a magnetized and rotating astrophysical object is numerically simulated with the purpose of investigating the outflow's magnetocentrifugal acceleration and eventual collimation. Gravity…

Astrophysics · Physics 2009-10-31 S. Bogovalov , K. Tsinganos

The topological and dynamical features of small scales are studied in the context of decaying magnetohydrodynamic turbulent flows using direct numerical simulations. Joint probability density functions (PDFs) of the invariants of gradient…

Fluid Dynamics · Physics 2015-06-15 Vassilios Dallas , Alexandros Alexakis

This work was motivated by a lacking general consensus in the exact form of the boundary conditions (BCs) required on the solid surfaces for the continuum modeling of RF plasmas. Various kinds of number and energy density BCs on solid…

Plasma Physics · Physics 2018-05-18 Althea Wilson , Babak Shotorban

The hydrodynamics of a flagellated microorganism is investigated when swimming close to a planar free-slip surface by means of numerical solu- tions of the Stokes equations obtained via a Boundary Element Method. Depending on the initial…

Fluid Dynamics · Physics 2017-03-31 Daniela Pimponi , Mauro Chinappi , Paolo Gualtieri , Carlo Massimo Casciola

We outline how to calculate the scalar damping term during a cosmological phase transition from kinetic theory. We determine the scalar damping rate from top quarks and weak gauge bosons in a Standard Model-like theory. We find that the…

High Energy Physics - Phenomenology · Physics 2025-12-19 Andreas Ekstedt , Thomas Konstandin , Jorinde van de Vis

It is shown that the smooth-wall boundary conditions specified for commonly used dissipation-based turbulence models are mathematically incorrect. It is demonstrated that when these traditional wall boundary conditions are used, the…

Computational Physics · Physics 2019-07-31 Douglas Hunsaker , Warren Phillips , Robert Spall

We consider the free fall of a sphere above a wall in a viscous incompressible fluid. We investigate the influence of boundary conditions on the finite-time occurrence of contact between the sphere and the wall. We prove that slip boundary…

Analysis of PDEs · Mathematics 2013-03-01 David Gérard-Varet , Matthieu Hillairet , Chao Wang

Massive circumstellar disks are prone to gravitational instabilities, which trigger the formation of spiral arms that can fragment into bound clumps under the right conditions. Two dimensional simulations of self-gravitating disks are…

Earth and Planetary Astrophysics · Physics 2017-10-11 Hans Baehr , Hubert Klahr , Kaitlin M. Kratter

Soft solids and their surface deformations control the response of many natural and artificial systems. Yet, their underlying properties are vigorously debated, particularly for polymer networks. While molecular-scale theories predict no…

We derive exact scaling laws for a three-dimensional incompressible helical two-fluid plasma, without the assumption of isotropy. For each ideal invariant of the two-fluid model, i.e. the total energy, the electron helicity and the proton…

Plasma Physics · Physics 2017-01-17 Nahuel Andrés , Sebastien Galtier , Fouad Sahraoui

We employ the first fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally-driven fragmentation of molecular clouds. The cores in an initially subcritical cloud develop…

Astrophysics · Physics 2008-11-26 Takahiro Kudoh , Shantanu Basu , Youichi Ogata , Takashi Yabe

Parameters of magnetic activity on the solar type stars depend on the properties of the dynamo processes operating in stellar convection zones. We apply nonlinear mean-field axisymmetric $\alpha^2\Omega$ dynamo models to calculate of the…

Solar and Stellar Astrophysics · Physics 2015-05-08 V. V. Pipin

We provide a rigorous analysis of the self-similar solution of the temporal turbulent boundary layer, recently proposed in [2], in which a body force is used to maintain a statistically steady turbulent boundary layer with periodic boundary…

Fluid Dynamics · Physics 2024-06-17 Andrew Wynn , Saeed Parvar , Joseph O Connor , Sylvain Laizet

Jupiter and Saturn exhibit alternating east-west jet streams as seen from surface. The origin of these zonal flows has been debated for decades. The high-precision gravity measurements by Juno mission and the grand finale of Cassini mission…

Earth and Planetary Astrophysics · Physics 2024-08-06 Shanshan Xue , Yufeng Lin

We study numerically the dynamo transition of an incompressible electrically conducting fluid filling the gap between two concentric spheres. In a first series of simulations, the fluid is driven by the rotation of a smooth inner sphere…

Fluid Dynamics · Physics 2012-11-13 K. Finke , A. Tilgner

We analyse the effect of confining rigid and elastic boundaries on the motility of a model dipolar microswimmer. Flexible boundaries are deformed by the velocity field of the swimmer in such a way that the motility of both extensile and…

Soft Condensed Matter · Physics 2015-06-15 Rodrigo Ledesma-Aguilar , Julia M. Yeomans