Effective buoyancy at the surface and aloft
Effective buoyancy at the surface and aloft
复制标题
水面和高处的有效浮力
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
D. Romps
中科院分区：
文献类型：
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作者：
N. Jeevanjee;D. Romps
这里表明，一个宽的、有浮力的空气团在水面上的加速速度远不如在高空中的快。特别是，分析公式推导出的有效浮力（即净垂直加速度，由于包裹浮力和环境响应）的理想化圆柱体的直径D和高度H，位于自由空间和表面。这些公式量化了有效浮力随长宽比D/H增加而减少的情况，并表明这种影响对于表面圆柱体更为明显，特别是当D/H > 1时。我们通过考虑这些浮力包裹产生的压力场来获得这些结果的直观性，并且我们用大涡模拟来检验我们的结果。我们的公式可以为云的垂直速度方程的参数化提供信息，并且还提供了流体静力和非流体静力区域之间数值模拟中的“灰色区域”的定量地图。
It is shown here that a wide, buoyant parcel of air at the surface accelerates far less rapidly than it does aloft. In particular, analytical formulae are derived for the effective buoyancy (i.e. the net vertical acceleration due to parcel buoyancy and environmental response) of idealized cylinders of diameter D and height H, located in free space and at the surface. These formulae quantify the decrease of effective buoyancy with increasing aspect ratio D/H, and show that this effect is more pronounced for surface cylinders, especially when D/H > 1. We gain intuition for these results by considering the pressure fields generated by these buoyant parcels, and we test our results with large‐eddy simulations. Our formulae can inform parametrizations of the vertical velocity equation for clouds, and also provide a quantitative map of the ‘grey zone’ in numerical modelling between hydrostatic and non‐hydrostatic regimes.