Events before droplet splashing on a solid surface
Events before droplet splashing on a solid surface
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DOI：
10.1017/s0022112009993594
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发表时间：
2010-03-25
影响因子：
3.7
通讯作者：
Brenner, Michael P.
中科院分区：
文献类型：
--
作者：
Mani, Madhav;Mandre, Shreyas;Brenner, Michael P.
液滴（约 1 mm）与固体表面之间的高速（约 1 m s(-1)）碰撞会产生飞溅。经典观察将这种飞溅的起源追溯到撞击点附近喷射出的一层薄薄的流体，尽管导致该薄层的流体机械机制尚不清楚。迄今为止，片材形成的机制依赖于液滴和表面的初始接触。在本文中，我们从理论上和数值上研究了大约 1μs 时间尺度内的事件，在这段时间内气体和液滴之间的耦合动力学变得很重要。液滴最初尝试通过从薄层排出气体或压缩薄层来接触基底，局部行为由控制方程的自相似解描述。这种相似性解决方案并不是渐近一致的：最初可以忽略不计的力变得相关并极大地改变了行为。根据液滴的半径和撞击速度，我们表明该解决方案被最初的次要物理效应所取代，例如液气界面的表面张力或液体中的粘性力。在低冲击速度下，表面张力阻止液滴冲击表面，而在较高速度下，粘性力在表面张力之前变得重要。一旦液滴粘度不能被忽略，界面的最终动力学尚不清楚。
A high-velocity (approximate to 1 m s(-1)) impact between a liquid droplet (approximate to 1 mm) and a solid surface produces a splash. Classical observations traced the origin of this splash to a thin sheet of fluid ejected near the impact point, though the fluid mechanical mechanism leading to the sheet is not known. Mechanisms of sheet formation have heretofore relied on initial contact of the droplet and the surface. In this paper, we theoretically and numerically study the events within the time scale of about 1 mu s over which the coupled dynamics between the gas and the droplet becomes important. The droplet initially tries to contact the substrate by either draining gas out of a thin layer or compressing it, with the local behaviour described by a self-similar solution of the governing equations. This similarity solution is not asymptotically consistent: forces that were initially negligible become relevant and dramatically change the behaviour. Depending on the radius and impact velocity of the droplet, we show that the solution is overtaken by initially subdominant physical effects such as the surface tension of the liquid gas interface or viscous forces in the liquid. At low impact velocities surface tension stops the droplet from impacting the surface, whereas at higher velocities viscous forces become important before surface tension. The ultimate dynamics of the interface once droplet viscosity cannot be neglected is not yet known.