Density currents in two‐layer shear flows
Density currents in two‐layer shear flows
复制标题
双层剪切流中的密度流
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
M. Xue
中科院分区：
文献类型：
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作者：
M. Xue
An earlier two‐fluid model of an idealized densitycurrent in low‐level shear is extended to include variable upper‐level shear. Far‐field solutions are determined, based on the conservation of mass, momentum and vorticity, and the conservation of Bernoulli function (energy) along streamlines for inviscid flows. It is found that the upper‐level and low‐level shears play similar roles in controlling the depth of steady‐state density‐currents. In most cases, large positive upper‐level shear supports a deeper density‐current and steeper front, and therefore a stronger updraught. It is also found that when the low‐level shear is weak and upper‐level shear occupies about half the domain depth, larger positive shear can result in a shallower rather than a deeper density‐current. This behaviour was not found for either constant shear flow or flows with only low‐level shear. The behaviour is understood by examining the flow structure and flow‐force components as a function of the upper‐level shear, Furthermore, by allowing the upper‐level shear to vary, an overturning flow is permitted ahead of the density current. This was not possible in the earlier model in which the upper‐level flow was assumed to be constant. The present extension allows us to draw closer analogues between the model solutions and the circulation patterns found in typical squalllines in sheared environments.
