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Among the candidates for generating turbulence in accretion discs in situations with low intrinsic ionization the vertical shear instability (VSI) has become an interesting candidate, as it relies purely on a vertical gradient in the…

Earth and Planetary Astrophysics · Physics 2016-10-19 Moritz H. R. Stoll , Wilhelm Kley

The standard magnetorotational instability (SMRI) is a promising mechanism for turbulence and rapid accretion in astrophysical disks. It is a magnetohydrodynamic (MHD) instability that destabilizes otherwise hydrodynamically stable disk…

We investigate the stability of stratified fluid layers undergoing homogeneous and periodic tidal deformation. We first introduce a local model which allows to study velocity and buoyancy fluctuations in a Lagrangian domain periodically…

Fluid Dynamics · Physics 2018-03-14 Thomas Le Reun , Benjamin Favier , Michael Le Bars

We study theoretically pressure driven planar channel flow of shear thinning viscoelastic fluids. Combining linear stability analysis and full nonlinear simulation, we study the instability of an initially one-dimensional base state to the…

Soft Condensed Matter · Physics 2019-08-09 Hugh J. Barlow , Ewan J. Hemingway , Andrew Clarke , Suzanne M. Fielding

Astrophysical discs which are sufficiently massive and cool are linearly unstable to the formation of axisymmetric structures. In practice, linearly stable discs of surface density slightly below the threshold needed for this instability…

Earth and Planetary Astrophysics · Physics 2025-01-22 Joshua J. Brown , Gordon I. Ogilvie

In this paper, we show that the quasi-one-dimensional flow of an ideal inviscid fluid in a corrugated pipe is parametrically unstable in certain frequency bands. First-order perturbation theory is used to analyze the stability of the flow,…

Fluid Dynamics · Physics 2021-02-09 Nikita V. Bykov

We perform 3D vertically-stratified local shearing-box ideal MHD simulations of the magnetorotational instability (MRI) that include a net vertical magnetic flux, which is characterized by beta_0 (ratio of gas pressure to magnetic pressure…

High Energy Astrophysical Phenomena · Physics 2015-06-11 Xue-Ning Bai , James M. Stone

Enhanced angular momentum transfer through the boundary layer near the surface of weakly magnetised accreting star is required in order to explain the observed accretion timescales in low-mass X-ray binaries, cataclysmic variables or young…

High Energy Astrophysical Phenomena · Physics 2018-11-07 V. V. Zhuravlev , D. N. Razdoburdin

We study the instability of a superfluid flow through a constriction in three spatial dimensions. We consider a Bose-Einstein condensate at zero temperature in two different geometries: a straight waveguide and a torus. The constriction…

Quantum Gases · Physics 2014-04-11 F. Piazza , L. A. Collins , A. Smerzi

We conduct three-dimensional hydrodynamic simulations to investigate the nonlinear outcomes and observability of vertical shear instability (VSI) in protoplanetary disks. Our models include both vertically isothermal and thermally…

Earth and Planetary Astrophysics · Physics 2024-12-16 Han-Gyeol Yun , Woong-Tae Kim , Jaehan Bae , Cheongho Han

The first consistent model for the turbulent tachocline is presented, with the turbulent diffusivity computed within the model instead of being specified arbitrarily. For the origin of the 3D turbulence a new mechanism is proposed. Owing to…

Astrophysics · Physics 2015-06-24 K. Petrovay

We present N-body simulations of unstable spiral modes in a dynamically cool collisionless disc. We show that spiral modes grow in a thin collisionless disk in accordance with the analytical perturbation theory. We use the particle-mesh…

Astrophysics · Physics 2009-11-13 A. V. Khoperskov , A. Just , V. I. Korchagin , M. A. Jalali

Analytical treatment of black hole accretion generally presumes the stability of the stationary configuration. Various authors in the past several decades demonstrated the validity of such an assumption for inviscid hydrodynamic flow.…

High Energy Astrophysical Phenomena · Physics 2014-06-17 Sankhasubhra Nag , Deepika B Ananda , Ishita Maity , Tapas K. Das

We derive a minimal continuum model to investigate the hydrodynamic mechanism behind the fingering instability recently discovered in a suspension of microrollers near a floor [Driscoll et al. Nature Physics, 2016]. Our model, consisting of…

Fluid Dynamics · Physics 2017-11-15 Blaise Delmotte , Michelle Driscoll , Aleksandar Donev , Paul Chaikin

We propose a new metric called s-LID based on the concept of Local Intrinsic Dimensionality to identify and quantify hierarchies of kinematic patterns in heterogeneous media. s-LID measures how outlying a grain's motion is relative to its s…

Materials Science · Physics 2021-04-06 Shuo Zhou , Antoinette Tordesillas , Mehdi Pouragha , James Bailey , Howard Bondell

We explore the linear stability of astrophysical discs exhibiting vertical shear, which arises when there is a radial variation in the temperature or entropy. Such discs are subject to a "vertical-shear instability", which recent nonlinear…

Solar and Stellar Astrophysics · Physics 2015-06-24 Adrian J. Barker , Henrik N. Latter

Many environmental, energy, and industrial processes involve the flow of polymer solutions in three-dimensional (3D) porous media where fluid is confined to navigate through complex pore space geometries. As polymers are transported through…

Fluid Dynamics · Physics 2024-12-05 Emily Y. Chen , Christopher A. Browne , Simon J. Haward , Amy Q. Shen , Sujit S. Datta

This work analyses the dynamical properties of periodically-driven band models. Focusing on the case of Bose-Einstein condensates, and using a meanfield approach to treat inter-particle collisions, we identify the origin of dynamical…

Quantum Gases · Physics 2017-05-10 S. Lellouch , M. Bukov , E. Demler , N. Goldman

We study the stability of standing shock waves in advection-dominated accretion flows into a Schwarzschild black hole by 2D general relativistic hydrodynamic simulations as well as linear analysis in the equatorial plane. We demonstrate…

Astrophysics · Physics 2009-11-13 Hiroki Nagakura , Shoichi Yamada

Internal waves are believed to be of primary importance as they affect ocean mixing and energy transport. Several processes can lead to the breaking of internal waves and they usually involve non linear interactions between waves. In this…

Fluid Dynamics · Physics 2015-06-12 Baptiste Bourget , Thierry Dauxois , Sylvain Joubaud , Philippe Odier