Simultaneous Effect of Droplet Temperature and Surface Wettability on Single Drop Impact Dynamics
Simultaneous Effect of Droplet Temperature and Surface Wettability on Single Drop Impact Dynamics
复制标题
液滴温度和表面润湿性对单液滴冲击动力学的同时影响
DOI：
10.1134/s0015462820040084
复制
发表时间：
2020
期刊：
影响因子：
0.9
通讯作者：
S. Ranjith
中科院分区：
文献类型：
--
作者：
P. Naveen;R. R. Simhadri;S. Ranjith
本文实验研究了液滴温度对单液滴撞击不同疏水性表面的热流体动力学的影响。液体温度的变化通常导致诸如密度、粘度、表面张力和焓的性质的改变，因此，液滴动力学得到修改。利用高速成像技术，研究了水滴在亲水、疏水和超疏水表面上的碰撞形态和铺展规律。在5至85°C的温度范围内和韦伯数在14.5至160之间的液滴中，定性和定量地监测液滴变形。据观察，随着液体温度的增加，由于固体表面的密度、表面张力、粘度和接触角的降低的综合效应，铺展因子增加。亲水、疏水和超疏水表面在极端温度下液滴延伸的差异分别为62.7%、27.76%和20.52%。在低温下，表面张力占主导地位，Cassie-Baxter状态在纹理化的超疏水表面上占主导地位，并且液滴反弹。相反，在升高的温度下，液-固界面破裂，液体渗透到空腔中并导致Wenzel状态。此外，发现在低温状态下表现出多次反弹的液滴在高液滴温度下粘附在超疏水基底上，而与韦伯数无关。
AbstractIn this paper, the influence of the liquid droplet temperature on thermo–hydrodynamics of a single droplet impinging on surfaces having different hydrophobicities is experimentally investigated. Variation in the liquid temperature typically results in alteration of properties such as the density, the viscosity, the surface tension, and the enthalpy, consequently, the droplet dynamics gets to be modified. Employing high-speed imaging technique, the morphology and spreading pattern are investigated for water droplet collision on hydrophilic, hydrophobic and super-hydrophobic surfaces. The droplet deformation is monitored qualitatively and quantitatively for drops in the temperature range from 5 to 85°C and the Weber number between 14.5 and 160. It is observed that with an increase in the liquid temperature the spreading factor increases owing to the combined effect of reduction in the density, the surface tension, the viscosity and the contact angle of the solid surface. The differences in extension of droplets under the extreme temperatures for hydrophilic, hydrophobic and super-hydrophobic surfaces are noted to be 62.7, 27.76, and 20.52%, respectively. At the low temperature, the surface tension force dominates and the Cassie–Baxter state prevails on a textured super-hydrophobic surface and the droplets bounce off. In contrast at elevated temperatures, the liquid–solid interface ruptures and liquid penetrates into the cavities and results in the Wenzel state. Furthermore, the drop which exhibits multiple bounces in the low temperature regime is found sticking on a super-hydrophobic substrate at the high droplet temperature irrespective of the Weber number.