Investigations on the impact of a drop onto a small spherical target
Investigations on the impact of a drop onto a small spherical target
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DOI：
10.1063/1.2716065
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发表时间：
2007-03-01
影响因子：
4.6
通讯作者：
Tropea, Cam
中科院分区：
文献类型：
--
作者：
Bakshi, Shamit;Roisman, Ilia V.;Tropea, Cam
本文报道了液滴撞击球形靶的实验和理论研究。测量了靶表面膜厚的空间和时间变化。从实验结果中可以清楚地看到三个不同的时间阶段的膜动力学，即初始液滴变形阶段，惯性占主导地位的阶段，和粘度占主导地位的阶段。实验还研究了液滴雷诺数和靶滴尺寸比对靶表面膜流动力学的影响。据观察，对于一个给定的目标滴尺寸比，无量纲的时间变化的膜厚度崩溃到一个单一的曲线在第一和第二阶段。在低雷诺数情况下，向粘性主导区的过渡发生得更早，残余厚度也更大。一个简化的准一维的方法已被用来模拟流动的球形目标。该理论考虑了惯性和粘性效应。重力和目标的曲率也被考虑在内。对于无粘的、惯性占主导地位的扩散阶段，得到了球体上随时间变化的膜轮廓的解析表达式。在此基础上，得到了粘性主导相北极附近膜厚的演化方程，并进行了求解。当液滴直径和目标直径的值相当时，在理论预测和测量之间观察到良好的一致性。模型中未使用可调参数。(c)2007年，美国物理学会。
This paper reports on experimental and theoretical investigations of the impact of a droplet onto a spherical target. Spatial and temporal variation of film thickness on the target surface is measured. Three distinct temporal phases of the film dynamics are clearly visible from the experimental results, namely the initial drop deformation phase, the inertia dominated phase, and the viscosity dominated phase. Experiments are also conducted to study the effect of droplet Reynolds number and target-to-drop size ratio on the dynamics of the film flow on the surface of the target. It is observed that for a given target-to-drop size ratio, the nondimensional temporal variation of film thickness collapses onto a single curve in the first and second phases. The transition to the viscosity dominated regime occurs earlier for the low Reynolds number cases and residual thickness is also larger. A simplified quasi-one-dimensional approach has been used to model the flow on the spherical target. The theory accounts for the inertial and viscous effects. Gravity and the curvature of the target are also taken into account. An analytical expression for the time-dependent film profile on the sphere is obtained for the inviscid, inertia dominated phase of spreading. Then, the evolution equation for the film thickness near the north pole in the viscosity dominated phase is obtained and solved. Good agreement is observed between the theoretical predictions and the measurements when the values of the drop and target diameters are comparable. No adjustable parameters have been used in the model. (c) 2007 American Institute of Physics.