Fluid Dynamics Experiments for Planetary Interiors

Abstract

Understanding fluid flows in planetary cores and subsurface oceans, as well as their signatures in available observational data (gravity, magnetism, rotation, etc.), is a tremendous interdisciplinary challenge. In particular, it requires understanding the fundamental fluid dynamics involving turbulence and rotation at typical scales well beyond our day-to-day experience. To do so, laboratory experiments are fully complementary to numerical simulations, especially in systematically exploring extreme flow regimes for long duration. In this review article, we present some illustrative examples where experimental approaches, complemented by theoretical and numerical studies, have been key for a better understanding of planetary interior flows driven by some type of mechanical forcing. We successively address the dynamics of flows driven by precession, by libration, by differential rotation, and by boundary topography.

Structure, Materials and Processes in the Earth’s Core and Mantle

“…7 Compilation of current approximate pressure-temperature capabilities of static high-pressure, hightemperature experimental equipment Mandea 2008). The theory of liquid convection in fast rotating planetary spherical shells is behind these variations, as also discussed in Le Bars et al (2021). For a fluid shell with a positive temperature gradient imposed between inner and outer core boundary, convection starts as columns outside the tangent cylinder (i.e., Inner Core Boundary, ICB) parallel to the Earth rotation axis (see Fig.…”

Transition to Equilibrium and Coherent Structure in Ideal MHD Turbulence

“…In regard to Earth, numerical simulations of the geodynamo [3][4][5] established that MHD processes within the Earth are capable of creating a magnetic field similar to the actual geomagnetic field, including reversals of the dominant dipole component. In addition, there have been many laboratory experiments [6], some of which have shown the growth of a self-generated magnetic field, i.e., a dynamo [7][8][9]. Although numerical simulations have been successful in proving the MHD nature of the geodynamo and experiments have shown a dynamo effect, the fundamental MHD origin of the dominant, quasi-steady geomagnetic dipole field still appear to be a theoretical mystery [10].…”

Inertial wave attractors in rapidly rotating tilted cuboids

“…For planets and moons, it is estimated that E∼Ofalse(10−14false), Ro∼Ofalse(10−5false) and Po∼Ofalse(10−7false) [1]. Such small E are unattainable in laboratory experiments, where the lower limit is E∼Ofalse(10−6false), and the forcing amplitudes are considerably larger in order to have reasonable signal-to-noise ratios [2,3]. The concept of extracting a portion of the available rotational energy in a rapidly rotating contained body of fluid via low-amplitude parametric forcing and converting it into intense fluid motions via the resonant excitation of inertial waves has a long history [4], and continues to be of great interest [5].…”