Convection with misaligned gravity and rotation: simulations and rotating mixing length theory
Convection with misaligned gravity and rotation: simulations and rotating mixing length theory
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DOI：
10.1093/mnras/staa372
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发表时间：
2020-04-01
影响因子：
4.8
通讯作者：
Browning, Matthew K.
中科院分区：
文献类型：
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作者：
Currie, Laura K.;Barker, Adrian J.;Browning, Matthew K.
我们提出了数值模拟，使用两个互补的设置，旋转Boussinesq热对流在一个三维的笛卡尔几何与错位的重力和旋转矢量。这个模型代表了一个星星或行星的对流带中非极地纬度的一个小区域。我们研究了旋转对不同纬度对流整体性质的影响，重点是确定热通量和温度梯度之间的关系。我们表明，我们的结果可以解释使用旋转混合长度理论（RMLT）。RMLT的最简单版本（由于史蒂文森）考虑了传输最多热量的单一模式。这在解释我们的结果方面相当有效，但在中纬度地区，这些预测有系统的偏离（温度梯度高达约30%）。我们开发了一个更详细的治疗RMLT，包括多种模式提供的运输，我们表明，这占了大部分的系统差异。我们还表明，对流产生的纬向流和纬向环流产生在我们的模拟，其性质强烈依赖于盒子的尺寸。这些气流也影响热输送，在某些纬度上导致偏离RMLT。然而，我们发现的理论预测的多模式理论的中层温度梯度，均方根（rms）的垂直速度，均方根温度波动，以及在不同纬度的热传输的空间谱都在合理的好协议与我们的数值计算结果时，纬向流很小。
We present numerical simulations, using two complementary set-ups, of rotating Boussinesq thermal convection in a three-dimensional Cartesian geometry with misaligned gravity and rotation vectors. This model represents a small region at a non-polar latitude in the convection zone of a star or planet. We investigate the effects of rotation on the bulk properties of convection at different latitudes, focusing on determining the relation between the heat flux and temperature gradient. We show that our results may be interpreted using rotating mixing length theory (RMLT). The simplest version of RMLT (due to Stevenson) considers the single mode that transports the most heat. This works reasonably well in explaining our results, but there is a systematic departure from these predictions (up to approximately 30 per cent in the temperature gradient) at mid-latitudes. We develop a more detailed treatment of RMLT that includes the transport afforded by multiple modes, and we show that this accounts for most of the systematic differences. We also show that convectively generated zonal flows and meridional circulations are produced in our simulations, and that their properties depend strongly on the dimensions of the box. These flows also affect the heat transport, contributing to departures from RMLT at some latitudes. However, we find the theoretical predictions of the multi-mode theory for the mid-layer temperature gradient, the root-mean-square (rms) vertical velocity, the rms temperature fluctuation, and the spatial spectrum of the heat transport at different latitudes are all in reasonably good agreement with our numerical results when zonal flows are small.