Ekman number
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Turbulent geodynamo simulations: a leap towards Earth’s core Open
We present an attempt to reach realistic turbulent regime in direct numerical simulations of the geodynamo. We rely on a sequence of three convection-driven simulations in a rapidly rotating spherical shell. The most extreme case reaches t…
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Scaling regimes in spherical shell rotating convection Open
Rayleigh–Bénard 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 proces…
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Laboratory-numerical models of rapidly rotating convection in planetary cores Open
We present laboratory and numerical models investigating the behavioural regimes of rapidly rotating convection in high-latitude planetary core-style settings. Our combined laboratory-numerical approach, utilizing simplified geometries, ca…
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Strong-field spherical dynamos Open
Numerical models of the geodynamo are usually classified into two categories: dipolar modes, observed when the inertial term is small enough; and multipolar fluctuating dynamos, for stronger forcing. We show that a third dynamo branch corr…
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Approaching a realistic force balance in geodynamo simulations Open
Significance Flow in Earth’s liquid core is expected to be primarily governed by the Coriolis force due to Earth’s rotation, the buoyancy force driving the convection, and the Lorentz force due to the geomagnetic field. A relevant geodynam…
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Turbulent Rotating Rayleigh–Bénard Convection Open
Rotation with thermally induced buoyancy governs many astrophysical and geophysical processes in the atmosphere, ocean, sun, and Earth's liquid-metal outer core. Rotating Rayleigh–Bénard convection (RRBC) is an experimental system that has…
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Force balance in numerical geodynamo simulations: a systematic study Open
SUMMARY Dynamo action in the Earth’s outer core is expected to be controlled by a balance between pressure, Coriolis, buoyancy and Lorentz forces, with marginal contributions from inertia and viscous forces. Current numerical simulations o…
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Subcritical Thermal Convection of Liquid Metals in a Rapidly Rotating Sphere Open
7 pages, 8 figures
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Advances in geodynamo modelling Open
This paper reviews the remarkable developments in numerical geodynamo simulations over the last few years. Simulations with Ekman numbers as low as E=10−8E=10−8 are now within reach and more and more details of the observed field are recov…
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The effects of Ekman pumping on quasi-geostrophic Rayleigh–Bénard convection Open
Numerical simulations of three-dimensional rapidly rotating Rayleigh–Bénard convection are performed by employing an asymptotic quasi-geostrophic model that incorporates the effects of no-slip boundaries through (i) parametrized Ekman pump…
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Atmospheric Ekman Flows with Variable Eddy Viscosity Open
We revisit the classical problem of the behaviour of the wind in the steady atmospheric Ekman layer. We show, for general variable eddy viscosities, that in the Northern Hemisphere the time-averaged ageostrophic wind profile always decays …
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The transition to Earth-like torsional oscillations in magnetoconvection simulations Open
Evidence for torsional oscillations (TOs) operating within the Earth's fluid outer core has been found in the secular variation of the geomagnetic field. These waves arise via disturbances to the predominant (magnetostrophic) force balance…
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Greater Role of Geostrophic Currents in Ekman Dynamics in the Western Arctic Ocean as a Mechanism for Beaufort Gyre Stabilization Open
Seven different methods, with and without including geostrophic currents, were used to explore Ekman dynamics in the western Arctic Ocean for the period 1992–2014. Results show that surface geostrophic currents have been increasing and are…
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The geostrophic regime of rapidly rotating turbulent convection Open
Rotating Rayleigh-Bénard convection is a simple model system used to study the interplay of buoyant forcing and rotation. Many recent studies have focused on the geostrophic regime of turbulent rotating convection where the principal balan…
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Precessing spherical shells: flows, dissipation, dynamo and the lunar core Open
SUMMARY Precession of planets or moons affects internal liquid layers by driving flows, instabilities and possibly dynamos. The energy dissipated by these phenomena can influence orbital parameters such as the planet’s spin rate. However, …
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Ekman-type solutions for shallow-water flows on a rotating sphere: A new perspective on a classical problem Open
An asymptotic analysis, based solely on a small shallow-water parameter, produces a generalisation of the classical Ekman spiral which combines all the relevant physical processes, including nonlinearity, in a balance of terms at leading o…
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Effect of shear and magnetic field on the heat-transfer efficiency of convection in rotating spherical shells Open
We study rotating thermal convection in spherical shells as prototype for flow in the cores of terrestrial planets, gas planets or in stars. We base our analysis on a set of about 450 direct numerical simulations of the (magneto)hydrodynam…
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Libration‐driven flows in ellipsoidal shells Open
Planets and satellites can undergo physical librations, which consist of forced periodic variations in their rotation rate induced by gravitational interactions with nearby bodies. This mechanical forcing may drive turbulence in interior f…
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Electro-osmotic flow in a rotating rectangular microchannel Open
An analytical model is presented for low-Rossby-number electro-osmotic flow in a rectangular channel rotating about an axis perpendicular to its own. The flow is driven under the combined action of Coriolis, pressure, viscous and electric …
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Analyses of external and global intermittency in the logarithmic layer of Ekman flow Open
Existence of non-turbulent flow patches in the vicinity of the wall of a turbulent flow is known as global intermittency. Global intermittency challenges the conventional statistics approach when describing turbulence in the inner layer an…
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Centrifugal and Symmetric Instability during Ekman Adjustment of the Bottom Boundary Layer Open
Flow along isobaths of a sloping lower boundary generates an across-isobath Ekman transport in the bottom boundary layer. When this Ekman transport is down the slope it causes convective mixing—much like a downfront wind in the surface bou…
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Morphological Classification of the Convective Regimes in Rotating Stars Open
We present a set of numerical simulations that model the convection zones of solar-like stars. With this suite of numerical experiments, we explore how the nature of the convective structures transitions through a series of morphological r…
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Competition between Ekman Plumes and Vortex Condensates in Rapidly Rotating Thermal Convection Open
We perform direct numerical simulations of rotating Rayleigh-Bénard convection (RRBC) of fluids with low (Pr=0.1) and high (Pr≈5) Prandtl numbers in a horizontally periodic layer with no-slip bottom and top boundaries. No-slip boundaries a…
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Unsteady Ekman‐Stokes Dynamics: Implications for Surface Wave‐Induced Drift of Floating Marine Litter Open
We examine Stokes drift and wave‐induced transport of floating marine litter on the surface of a rotating ocean with a turbulent mixed layer. Due to Coriolis‐Stokes forcing and surface wave stress, a second‐order Eulerian‐mean flow forms, …
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Generation and maintenance of bulk turbulence by libration-driven elliptical instability Open
Longitudinal libration corresponds to the periodic oscillation of a body’s rotation rate and is, along with precessional and tidal forcings, a possible source of mechanically-driven turbulence in the fluid interior of satellites and planet…
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Axisymmetric inertial modes in a spherical shell at low Ekman numbers Open
We investigate the asymptotic properties of axisymmetric inertial modes propagating in a spherical shell when viscosity tends to zero. We identify three kinds of eigenmodes whose eigenvalues follow very different laws as the Ekman number $…
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The Ekman spiral for piecewise-uniform viscosity Open
We re-visit Ekman's (1905) classic problem of wind-stress-induced ocean currents to help interpret observed deviations from Ekman's theory, in particular from the predicted surface current deflection of 45∘. While previous studies have sho…
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Rotating double-diffusive convection in stably stratified planetary cores Open
SUMMARY In planetary fluid cores, the density depends on temperature and chemical composition, which diffuse at very different rates. This leads to various instabilities, bearing the name of double-diffusive convection (DDC). We investigat…
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Resonance phenomena in a time-dependent, three-dimensional model of an idealized eddy Open
We analyze the geometry of Lagrangian motion and material barriers in a time-dependent, three-dimensional, Ekman-driven, rotating cylinder flow, which serves as an idealization for an isolated oceanic eddy and other overturning cells with …
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Heat-transport scaling and transition in geostrophic rotating convection with varying aspect ratio Open
We present high-precision experimental and numerical studies of the Nusselt\nnumber $Nu$ as functions of the Rayleigh number $Ra$ in geostrophic rotating\nconvection with domain aspect ratio ${\\Gamma}$ varying from 0.4 to 3.8 and the\nEkm…