Enhanced droplet collision rates and impact velocities in turbulent flows: The effect of poly-dispersity and transient phases
Enhanced droplet collision rates and impact velocities in turbulent flows: The effect of poly-dispersity and transient phases
复制标题
增强湍流中的液滴碰撞率和冲击速度：多分散性和瞬态相的影响
DOI：
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发表时间：
2017
影响因子：
4.6
通讯作者：
Samriddhi Sankar Ray
中科院分区：
文献类型：
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作者：
M. James;Samriddhi Sankar Ray
我们比较了二维和三维湍流平流作用下多分散悬浮液中不同尺寸液滴之间的碰撞率和典型碰撞速度。结果表明，对于碰撞对间尺寸比较大的液滴，其碰撞速率在过渡阶段得到了提高，并得到了粒子对碰撞速度与其相对尺寸关系的精确理论估计。这些分析结果与我们直接数值模拟的数据进行了验证。我们的结果表明，液滴的快速增长，例如在温暖的云中，很可能是由于粒子在瞬变阶段的动力学所致，在瞬变阶段，大小粒子之间的碰撞速率增加可能导致失控过程。我们的结果对于模拟合并或破碎(取决于撞击速度)也是重要的，并且将是至关重要的，例如，在这样的系统中获得精确的合并核。
We compare the collision rates and the typical collisional velocities amongst droplets of different sizes in a poly-disperse suspension advected by two- and three-dimensional turbulent flows. We show that the collision rate is enhanced in the transient phase for droplets for which the size-ratios between the colliding pairs is large as well as obtain precise theoretical estimates of the dependence of the impact velocity of particles-pairs on their relative sizes. These analytical results are validated against data from our direct numerical simulations. Our results suggest that an explanation of the rapid growth of droplets, e.g., in warm clouds, may well lie in the dynamics of particles in transient phases where increased collision rates between large and small particles could result in runaway process. Our results are also important to model coalescence or fragmentation (depending on the impact velocities) and will be crucial, for example, in obtaining precise coalescence kernels in such systems.