On the internal shear layers spawned by the critical regions in oscillatory Ekman boundary layers
On the internal shear layers spawned by the critical regions in oscillatory Ekman boundary layers
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DOI：
10.1017/s0022112095003326
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发表时间：
1995-09
影响因子：
3.7
通讯作者：
R. Kerswell
中科院分区：
文献类型：
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作者：
R. Kerswell
在快速旋转的系统中，与小振荡流相关的Ekman边界层标度在临界纬度处是众所周知的。这些异常边界区域对内部流动的影响一直是人们关注的问题。利用Stewartson（1957）分裂圆盘构型模型问题的分析结果，我们认为这些边界区产生了内部剪切层。这些剪切层的自然长度尺度为E1/3，如果边界在临界纬度处凹离流体，则其速度仅小于Rossby数O（E1/6），其中E是Ekman数。否则，只有一个较弱的剪切层产生的长度尺度E1/5包含速度的O（E3/10）小于罗斯比数，而不是通常的O（E1/5）值的粘性流在内部。我们展示了这些层是如何通过自身或更显著地与内部无粘流相结合来携带角动量的，从而影响领先阶的平均流。这些结论，然后讨论的背景下，旋进扁球体的流体，详细的实验观察。
The Ekman boundary layer scalings associated with small oscillatory flows in a rapidly rotating system are well known to break down at the critical latitudes. The effect of these anomalous boundary regions on the interior flow has long been an issue of some concern. We argue, using analytical results derived in a model problem based on Stewartson's (1957) split-disk configuration, that these boundary regions spawn internal shear layers. These shear layers have their natural length scale of E1/3 and carry velocities only O(E1/6) smaller than the Rossby number – where E is the Ekman number – if the boundary is concave away from the fluid at the critical latitude. Otherwise, only a weaker shear layer is produced of length scale E1/5 containing velocities of O(E3/10) smaller than the Rossby number rather than the usual O(E1/5) value for viscous flows in the interior. We show how these layers can carry angular momentum by themselves or more significantly in combination with the interior inviscid flow, so as to influence the mean flow at leading order. These conclusions are then discussed in the context of a precessing oblate spheroid of fluid for which detailed experimental observations are available.