Caustic activation of rain showers.
Caustic activation of rain showers.
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DOI：
10.1103/physrevlett.97.048501
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发表时间：
2006-04
影响因子：
8.6
通讯作者：
M. Wilkinson;B. Mehlig;V. Bezuglyy
中科院分区：
文献类型：
--
作者：
M. Wilkinson;B. Mehlig;V. Bezuglyy
我们定量地展示了湍流空气中可见湿气液滴的碰撞率如何在湍流强度超过阈值时突然增加，这是由于它们的速度场中形成了褶皱焦散。焦散的形成是一个被激活的过程，在这个过程中，湍流强度的测量，称为斯托克斯数St，类似于化学反应中的温度：碰撞速率包含一个因子exp（-C/St）。我们的结果与解释对流云快速降雨的长期问题有关。我们的理论不涉及粒子的空间聚类。
We show quantitatively how the collision rate of droplets of visible moisture in turbulent air increases very abruptly as the intensity of the turbulence passes a threshold, due to the formation of fold caustics in their velocity field. The formation of caustics is an activated process, in which a measure of the intensity of the turbulence, termed the Stokes number St, is analogous to temperature in a chemical reaction: the rate of collision contains a factor exp(-C/St). Our results are relevant to the long-standing problem of explaining the rapid onset of rainfall from convecting clouds. Our theory does not involve spatial clustering of particles.