Spreading behavior of an impacting drop on a structured rough surface
Spreading behavior of an impacting drop on a structured rough surface
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DOI：
10.1063/1.2033627
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发表时间：
2005-10-01
影响因子：
4.6
通讯作者：
Nishiyama, H
中科院分区：
文献类型：
--
作者：
Sivakumar, D;Katagiri, K;Nishiyama, H
对水滴撞击结构粗糙表面的传播进行了实验研究。粗糙表面经过特殊处理，表面粗糙度图案规则。方形表面粗糙度的排列在表面上形成沟槽状凹槽。视频显微镜和受控的光曝光系统被用来构建扩散过程的图像序列。对图像进行数字分析，以测量扩散液滴直径2R的时间变化。给出了三种表面粗糙度在100-500微米范围内变化的结果，以及韦伯数WE在35-225范围内的不同撞击跌落条件下的结果。2R随时间变化的结果表明，在结构化粗糙表面上，扩展同时发生在表面纹理图案的内部和上方。对于给定的表面几何形状，在表面凹槽内流动的液体体积随着We的增加而增加。因此，在织构图案内部测量的2R值大于在织构图案上方测量的2R值，并且它们的差异随着We的增加而增大。表面粗糙度的排列影响着撞击液滴的轴对称扩散规律。对于本研究中使用的织构几何形状，在低We滴落的影响下，扩散图案类似于规则的菱形形状，并且在高We时变得复杂。如果粗糙表面的粗糙高度小于扩散液体薄片的厚度，则在结构化粗糙表面的织构图案内部和之上测量的扩散距离更接近于在光滑表面上记录的测量值；然而，表面粗糙度对扩散图案的影响很大，并产生液体飞溅。(C)2005年美国物理研究所。
The spreading of water drops impinging on structured rough surfaces is studied experimentally. The rough surfaces are specially prepared with a regular pattern of surface asperities. The arrangement of the square-shaped surface asperities creates channel-like grooves on the surface. A video microscope along with a controlled light exposure system is used to construct the image sequences of the spreading process. The images are digitally analyzed to measure the temporal variation of the spreading drop diameter 2R. Results are obtained for three rough surfaces with varying asperity heights in the range of 100-500 mu m and for different impact drop conditions with Weber number We in the range of 35-225. The results on the temporal variation of 2R show that, on the structured rough surfaces, the spreading occurs simultaneously both inside and above the texture pattern of the surfaces. For a given surface geometry, the volume of liquid flowing inside the grooves of the surface increases with increasing We. Consequently, the values of 2R measured inside the texture pattern are larger than those measured above the texture pattern, and their difference increases with increasing We. The arrangement of the surface asperities influences the spreading pattern of an impacting drop spreading axisymmetrically. For the texture geometry used in the present study, the spreading pattern resembles a regular rhombus shape for the impact of low We drops and becomes complex at high We. The spreading distances, measured both inside and above the texture pattern of the structured rough surfaces, are nearer to the measurements recorded on the smooth surface if the asperity height of the rough surface is smaller than the thickness of the spreading liquid lamella; however, the surface asperities influence the spreading pattern drastically and create a liquid splash. (c) 2005 American Institute of Physics.