Turbulent flows driven by the libration of an ellipsoidal container

Turbulent flows driven by the libration of an ellipsoidal container

Favier, B.
Grannan, A.
Le Bars, M.
Aurnou, J.

2015-08-28

We present a combination of laboratory experiments and numerical simulations modelling a geophysically relevant mechanical forcing: libration. Longitudinal libration corresponds to the periodic oscillation of a body's rotation and is, along with precessional and tidal forcings, a possible source of turbulence in the fluid interior of satellites and planets. In this study, we investigate the fluid motions inside a librating tri-axial ellipsoidal container filled with an incompressible fluid. The turbulent flow is driven by the elliptic instability which is a triadic resonance between two inertial modes and the base flow with elliptical streamlines. This is called the libration driven elliptical instability (LDEI). We characterize the transition to turbulence as triadic resonances develop while also investigating the properties of the turbulent flow that displays both intermittent or sustained regimes. The existence of such intense flows may play an important in understanding the thermal and magnetic evolution of bodies subject to mechanical forcing, which is not considered in standard models of convectively-driven magnetic field generation.

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