Gravity currents in the laboratory, atmosphere, and ocean
Gravity currents in the laboratory, atmosphere, and ocean
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DOI：
10.1146/annurev.fl.14.010182.001241
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发表时间：
1982
影响因子：
27.7
通讯作者：
J. Simpson
中科院分区：
文献类型：
--
作者：
J. Simpson
重力流或“密度流”是一种流体在另一种流体中的流动，这种流动是由流体之间的密度差异引起的。提供驱动力的比重的差异可能是由于溶解或悬浮的物质或温差造成的。重力流主要是水平的，要么以顶部或底部边界流的形式出现，要么以某种中间水平的侵入形式出现。流体通常是可混溶的，由此产生的混合在流动的动力学中起着重要作用。由于重力流是在许多不同的自然情况下形成的，也可能是人为的，因此对其性质的了解在许多科学学科中都是重要的。在大气中，雷暴外流和海风锋面是相对寒冷的稠密空气的重力流。大气悬浮重力流包括空气中雪粒的雪崩，也包括火山喷发产生的气体和固体形成的烈性雪崩和基潮。重力流在飞机安全、大气污染、昆虫学和虫害防治方面有着重要的应用，特别是在稠密气体技术中。可能形成重力流的工业事故包括意外泄漏的致密气体扩散。在海洋中，重力流是由盐度和温度不均匀驱动的，或者是以浊流的形式驱动的，其密度来自悬浮的泥沙或淤泥。海洋表面上的泡沫和碎片线可能表明重力流的前沿，这通常是由潮汐过程带来的。后者还影响重力流的行为，如表面的河流羽流和河床上的盐楔。与海上石油泄漏有关的重要问题一直是本系列的一篇综述论文(霍尔特1972)的主题。
A gravity current, or "density current," is the flow of one fluid within another caused by the density difference between the fluids. The difference in specific weight that provides the driving force may be due to dissolved or suspended material or to temperature differences. Gravity currents are primarily horizontal, occurring as either top or bottom boundary currents, or as intrusions at some intermediate level. The fluids are usually miscible and the mixing that results can play an important part in the dynamics of the flow. Since gravity currents are formed in many different natural situations and may also be man-made, knowledge of their properties is of importance in many scientific disciplines. In the atmosphere, thunderstorm outflows and sea-breeze fronts are gravity currents of relatively cold dense air. Atmospheric-suspension gravity currents include avalanches of airborne snow particles, also fiery avalanches and base surges formed from gases and solids issuing from volcanic eruptions. Gravity currents have important applications in aircraft safety, atmo spheric pollution, entomology and pest control, and especially in dense-gas technology. Industrial accidents in which gravity currents may be formed include the spread of a dense gas from an accidental release. In the ocean, gravity currents are driven by salinity and temperature inhomogeneities, or as turbidity currents whose density derives from sus pended mud or silt. Lines of foam and debris on the ocean surface may indicate the front of a gravity current, frequently brought about by tidal processes. The latter also affect the behavior of gravity currents such as river plumes at the surface and salt wedges on a river bed. The important problems related to oil spillage on the sea have been the subject of a review paper in this series (Hoult 1972).