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A generalized physics-based expression for the drag coefficient of spherical particles moving in a fluid is derived. The proposed correlation incorporates essential rarefied physics, low-speed hydrodynamics, and shock-wave physics to…

We consider rotating, kinematic dynamos at low magnetic Prandtl number $Pm$. We show that the inclusion of rotation leads to an increase in spatio-temporal coherence and a modification of the turbulent spectrum. These effects make the flow…

Fluid Dynamics · Physics 2018-11-06 Vassilios Dallas , Steve Tobias

The dynamics of a small rigid spherical particle in an unbounded pulsating vortex is considered, keeping constant the particle Stokes number St and varying the particle-to-fluid density ratio $\varrho$ and the pulsation frequency of the…

Fluid Dynamics · Physics 2018-11-14 Francesco Romanò

We study the changes in the dynamical behaviour of axisymmetric spherical mean-field dynamo models produced by changes in their geometry and topology, by considering a two parameter family of models, ranging from a full sphere to spherical…

Astrophysics · Physics 2007-05-23 E. Covas , R. Tavakol , A. Tworkowski , A. Brandenburg , J. Brooke , D. Moss

Magnetic activity changes the gravito-acoustic modes of solar-like stars and in particular their frequencies. There is an angular-degree dependence that is believed to be caused by the non-spherical nature of the magnetic activity in the…

Solar and Stellar Astrophysics · Physics 2019-06-26 F. Perez Hernandez , R. A. Garcia , S. Mathur , A. R. G. Santos , C. Regulo

Differential rotation plays a crucial role in the alpha-omega dynamo, and thus also in creation of magnetic fields in stars with convective outer envelopes. Still, measuring the radial differential rotation on stars is impossible with the…

Astrophysics · Physics 2009-11-13 H. Korhonen , D. Elstner

Using direct numerical simulations of three-dimensional hydromagnetic turbulence, either with helical or non-helical forcing, we show that the ratio of kinetic-to-magnetic energy dissipation always increases with the magnetic Prandtl…

Solar and Stellar Astrophysics · Physics 2014-07-25 Axel Brandenburg

A theoretical expression for the drag on a spherical bubble is derived for the entire range from very viscous to inertial flow conditions. It is based on a solution for only that part of the velocity profile that determines the drag. It is…

Fluid Dynamics · Physics 2022-04-08 Qiang Sun , Evert Klaseboer

Rayleigh-B\'enard convection in rotating spherical shells can be considered as a simplified analogue of many astrophysical and geophysical fluid flows. Here, we use three-dimensional direct numerical simulations to study this physical…

Fluid Dynamics · Physics 2016-11-23 T. Gastine , J. Wicht , J. Aubert

We perform numerical simulation of dynamo with magnetic Prandtl number $\mathrm{Pm} =0.2$ on $1024^3$ grid, and compute the energy fluxes and the shell-to-shell energy transfers. These computations indicate that the magnetic energy growth…

Fluid Dynamics · Physics 2015-06-26 Rohit Kumar , Mahendra K. Verma , Ravi Samtaney

The research is devoted to the stability of convective flow in a nonuniformly rotating layer of an electrically conducting fluid in a spiral magnetic field. The stationary and oscillatory modes of magnetic convection are considered…

Plasma Physics · Physics 2019-05-15 M. I. Kopp , A. V. Tur , V. V. Yanovsky

We numerically investigate the efficiency of a spherical Couette flow at generating a self-sustained magnetic field. No dynamo action occurs for axisymmetric flow while we always found a dynamo when non-axisymmetric hydrodynamical…

Geophysics · Physics 2020-07-17 Céline Guervilly , Philippe Cardin

We investigate dynamo action in global compressible solar-like convective dynamos in the framework of mean-field theory. We simulate a solar-type star in a wedge-shaped spherical shell, where the interplay between convection and rotation…

Solar and Stellar Astrophysics · Physics 2018-01-17 Jörn Warnecke , Matthias Rheinhardt , S. Tuomisto , Petri J. Käpylä , Maarit J. Käpylä , Axel Brandenburg

This work tackles a significant challenge in dynamo theory: the possibility of long-term amplification and maintenance of an axisymmetric magnetic field. We introduce a novel model that allows for non-trivial axially-symmetric steady-state…

Earth and Planetary Astrophysics · Physics 2025-07-08 Naoki Sato , Kumiko Hori

Contemporary three-dimensional physics-based simulations of the solar convection zone disagree with observations. They feature differential rotation substantially different from the true rotation inferred by solar helioseismology and…

Solar and Stellar Astrophysics · Physics 2023-11-23 Parag Gupta , David MacTaggart , Radostin D. Simitev

This work provides a recipe for creating drag, lift and torque closures for static assemblies of axisymmetric, non-spherical particles. Apart from Reynolds number $Re$ and solids volume fraction $\epsilon_s$, we propose four additional…

Fluid Dynamics · Physics 2020-11-10 Sathish K. P. Sanjeevi , Johan T. Padding

We consider the nonlinear Duffing oscillator in presence of fractional damping which is characteristic in different physical situations. The system is studied with a smaller and larger damping parameter value, that we call the underdamped…

Chaotic Dynamics · Physics 2024-03-18 Mattia Coccolo , Jesús M. Seoane , Stefano Lenci , Miguel A. F. Sanjuán

The dynamo driven by the magnetorotational instability (MRI) is believed to play an important role in the dynamics of accretion discs and may also explain the origin of the extreme magnetic fields present in magnetars. Its saturation level…

High Energy Astrophysical Phenomena · Physics 2022-09-21 Jerome Guilet , Alexis Reboul-Salze , Raphael Raynaud , Matteo Bugli , Basile Gallet

Convection is the main heat transport mechanism in the Earth's liquid core and is thought to power the dynamo that generates the geomagnetic field. Core convection is strongly constrained by rotation while being turbulent. Given the…

Fluid Dynamics · Physics 2025-02-28 Céline Guervilly , Emmanuel Dormy

Small-scale dynamos play important roles in modern astrophysics, especially on Galactic and extragalactic scales. Owing to dynamo action, purely hydrodynamic Kolmogorov turbulence hardly exists and is often replaced by hydromagnetic…

Astrophysics of Galaxies · Physics 2022-12-20 A. Brandenburg , I. Rogachevskii , J. Schober