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- Ulrich R Christensen, Andreas Tilgner
- Nature
- 2004

In the Earth's fluid outer core, a dynamo process converts thermal and gravitational energy into magnetic energy. The power needed to sustain the geomagnetic field is set by the ohmic losses (dissipation due to electrical resistance). Recent estimates of ohmic losses cover a wide range, from 0.1 to 3.5 TW, or roughly 0.3-10% of the Earth's surface heat… (More)

- Douglas H. Kelley, Daniel S. Zimmerman, +6 authors DANIEL P. LATHROPx
- 2007

Inertial waves driven by differential rotation in a planetary geometry Douglas H. Kelley a; Santiago Andrés Triana a; Daniel S. Zimmerman a; Andreas Tilgner b; Daniel P. Lathrop c a Department of Physics and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD, 20742, USA b Institute of Geophysics, University… (More)

- A Tilgner
- Physical review letters
- 2007

Inertial modes are oscillatory modes in rotating fluids. Shear layers appear in inertial modes in spherical shells that become singularities in the inviscid limit. It is shown here that the nonlinearity in the shear layers drives a zonal flow whose amplitude diverges in the inviscid limit. These results are relevant for the dynamics of planets and stars in… (More)

- Stefan Bernhard, Stefan Möhlenkamp, Andreas Tilgner
- Biomedical engineering online
- 2006

BACKGROUND
The pressure drop-flow relations in myocardial bridges and the assessment of vascular heart disease via fractional flow reserve (FFR) have motivated many researchers the last decades. The aim of this study is to simulate several clinical conditions present in myocardial bridges to determine the flow reserve and consequently the clinical relevance… (More)

Using direct simulations, weakly nonlinear theory and nonlinear mean-field theory, it is shown that the quenched velocity field of a saturated nonlinear dynamo can itself act as a kinematic dynamo. The flow is driven by a forcing function that would produce a Roberts flow in the absence of a magnetic field. This result confirms an analogous finding by F.… (More)

Direct numerical simulations of Rayleigh-Bénard convection in a plane layer with periodic boundary conditions at Rayleigh numbers up to 10(7) show that flow structures can be objectively classified as large or small scale structures because of a gap in spatial spectra. The typical size of the large scale structures does not always vary monotonically as a… (More)

Numerical simulation of rotating convection in plane layers with free slip boundaries show that the convective flows can be classified according to a quantity constructed from the Reynolds, Prandtl, and Ekman numbers. Three different flow regimes appear: laminar flow close to the onset of convection, turbulent flow in which the heat flow approaches the heat… (More)

It is found that for Taylor numbers of the order 10(8) quadrupolar dynamos aligned with the axis of rotation are preferred in comparison with dipolar dynamos. This preference holds for a range of Prandtl numbers P and magnetic Prandtl numbers P(m) in the neighborhood of unity. The main time-dependent feature of the quadrupolar dynamos are polward traveling… (More)

We describe a new phenomenon of zonal wind generation by tidal forcing. Following a recent theoretical and numerical analysis [A. Tilgner, Phys. Rev. Lett. 99, 194501 (2007)], we present the first experimental evidence that the nonlinear self-interaction of a tidally forced inertial mode can drive an intense axisymmetric flow in a rotating deformed sphere.… (More)

We investigate kinematic dynamos in cylinders and spheres surrounded by an insulator. The flow volume is divided into an inner region, in which the conducting fluid is in motion, and an outer region enclosing the inner one, in which the conductor is at rest. The dependence of the critical magnetic Reynolds number on the thickness of the outer conducting… (More)