Effects of fluid rheology and wetting properties on the droplet motion by a shear flow
Effects of fluid rheology and wetting properties on the droplet motion by a shear flow
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流体流变学和润湿特性对剪切流液滴运动的影响
DOI：
10.1002/pamm.201900068
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Janoske U.
中科院分区：
文献类型：
--
作者：
Barwari B;Burgmann S;Rohde M;Janoske U.
本文以水、甘油和乙醇液滴在PMMA和涂覆硅片表面的特殊情况为例，对液滴在湍流气流作用下的脱落机理进行了实验研究。使用带有可更换基板的矩形有机玻璃通道(22 X 22 Mm)。在实验过程中，建立并增加了可控的气流，直到液滴变形并开始沿表面从其初始位置移动。应用阴影技术测量了液滴的行为。图像通过边缘检测算法自动分析，以获得关于液滴轮廓、接触角和接触线运动的信息。研究发现，液滴开始运动所需的临界速度随着液滴体积的增大而减小。随着液滴粘度的增加，临界速度也随之增加。对于特定的液体，由于衬底的疏水性增加，与PMMA相比，更容易分离涂层硅片上的液滴。由于高粘性阻尼，甘油液滴在表面上的移动速度很慢，只有在较高的空气速度下才能到达某个位置。结果表明，接触角滞后似乎不是影响临界速度的唯一因素，因为多个参数叠加并影响液滴脱离过程。
The paper presents an experimental investigation of the detaching mechanisms of adhering droplets exposed to a turbulent air flow, focusing on the specific case of water, glycerine and ethanol droplets on a PMMA and coated silicon wafer surface. A rectangular Plexiglas channel (22 x 22 mm) with a replaceable substrate is used. A controlled air flow is established and increased during the experiment, until the droplet deforms and starts to move from its initial position along the surface. Shadowgraph technique is applied to measure the droplet behavior. The images are automatically analyzed by an edge‐detection algorithm to gain information on the droplet contour, the contact angles and the contact line movement. It was found that the critical velocity required for the onset of the droplet movement decreases with the droplet volume. As the viscosity of the droplet increases, the critical velocity increases. For a particular liquid it is easier to detach the droplets on coated silicon wafers compared to PMMA due to the increase of the hydrophobicity of the substrate. Glycerine droplets move at a slow rate over the surface due to the high viscous damping and reach a certain position only at higher air velocities. The results show that contact angle hysteresis seems not to be the unique factor influencing the critical velocity, since several parameters superpose and affect the droplet detachment process.
受控气流在振动板上的液滴变形、振荡和分离
DOI：
--
发表时间：
2018
期刊：
Pamm
影响因子：
--
作者：
Beawer Barwari;S. Burgmann;U. Janoske
通讯作者：
U. Janoske