Tide‐driven shear instability in planetary liquid cores
Tide‐driven shear instability in planetary liquid cores
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DOI：
10.1002/2014gl061434
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发表时间：
2014-09
影响因子：
5.2
通讯作者：
A. Sauret;M. Le Bars;P. Le Gal
中科院分区：
文献类型：
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作者：
A. Sauret;M. Le Bars;P. Le Gal
本文对潮汐强迫作用下的行星液核剪切不稳定性进行了实验研究。实验装置由一个充满水的可变形球体组成，该球体绕其轴线旋转，并受到椭圆力的作用。在共振强迫频率下，激励惯性模的非线性自相互作用驱动了一种强烈的局域轴对称射流。由于剪切不稳定，射流在低Ekman数时变得不稳定。利用粒子图像测速技术，我们推导出了一个半经验标度律，它捕捉到了剪切不稳定性的不稳定性阈值。这一机制与行星系统完全相关，在行星系统中，它构成了在其液核中产生湍流的新途径。
We present an experimental study on the shear instability driven by tidal forcing in a model planetary liquid core. The experimental setup consists of a water‐filled deformable sphere rotating around its axis and subjected to an elliptical forcing. At resonant forcing frequencies, the nonlinear self‐interaction of the excited inertial mode drives an intense and localized axisymmetric jet. The jet becomes unstable at low Ekman number because of a shear instability. Using particle image velocimetry measurements, we derive a semiempirical scaling law that captures the instability threshold of the shear instability. This mechanism is fully relevant to planetary systems, where it constitutes a new route to generate turbulence in their liquid cores.