Effect of Materials’ Wettability on the Dynamic Behavior of Droplet Impact onto a Rough Solid Surface

2011 ◽  
Vol 320 ◽  
pp. 341-346
Author(s):  
Jing Cui ◽  
Yang Liu ◽  
Wei Zhong Li ◽  
Ning Zhang
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Liquid Droplet ◽  
Droplet Impact ◽  
Apparent Contact Angle ◽  
Bottom Surface ◽  
Roughness Elements ◽  
Hydrophilic Material ◽  
Boltzmann Method ◽  
Intrinsic Contact Angle

In this paper, the effect of material’s wettability on the droplet impact has been investigated by numerical apporach. The unsteady flow behaviors of liquid droplet impacting against the rough solid surface with different wettabilities have been simulated based on lattice Boltzmann method. The spreading and bounding characterisitcs of droplet have been discussed. For the hydrophilic material, the droplet will sink into the grooves among roughness bumps, and its apparent contact angle in steady stead will be smaller than its corresponding intrinsic contact angle; while for the hydrophilic material, droplet will flow into the grooves but suspend on the top of roughness elements without any contacting with the bottom surface, and the apparent contact angle is larger than its intrinsic contact angle.

scholarly journals Pressure generated at the instant of impact between a liquid droplet and solid surface

2018 ◽  
Vol 5 (12) ◽  
pp. 181101 ◽  
Author(s):  
Y. Tatekura ◽  
M. Watanabe ◽  
K. Kobayashi ◽  
T. Sanada
Keyword(s):  
Solid Surface ◽  
Shape Factor ◽  
Liquid Droplet ◽  
Pressure Rise ◽  
Propagation Speed ◽  
Spherical Shape ◽  
Water Hammer ◽  
Droplet Impact ◽  
Maximum Pressure ◽  
The Impact

The prime objective of this study is to answer the question: How large is the pressure developed at the instant of a spherical liquid droplet impact on a solid surface? Engel first proposed that the maximum pressure rise generated by a spherical liquid droplet impact on a solid surface is different from the one-dimensional water-hammer pressure by a spherical shape factor (Engel 1955 J. Res. Natl Bur. Stand. 55 (5), 281–298). Many researchers have since proposed various factors to accurately predict the maximum pressure rise. We numerically found that the maximum pressure rise can be predicted by the combination of water-hammer theory and the shock relation; then, we analytically extended Engel’s elastic impact model, by realizing that the progression speed of the contact between the gas–liquid interface and the solid surface is much faster than the compression wavefront propagation speed at the instant of the impact. We successfully correct Engel’s theory so that it can accurately provide the maximum pressure rise at the instant of impact between a spherical liquid droplet and solid surface, that is, no shape factor appears in the theory.

scholarly journals Characterizing surface wetting and interfacial properties using enhanced sampling (SWIPES)

Soft Matter ◽  
2019 ◽  
Vol 15 (5) ◽  
pp. 860-869 ◽  
Author(s):  
Hao Jiang ◽  
Suruchi Fialoke ◽  
Zachariah Vicars ◽  
Amish J. Patel
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Solid Surface ◽  
Efficient Method ◽  
Liquid Surface ◽  
Liquid Droplet ◽  
Interfacial Properties ◽  
Enhanced Sampling ◽  
Surface Wetting ◽  
Liquid Surface Tension

We introduce an accurate and efficient method for characterizing surface wetting and interfacial properties, such as the contact angle made by a liquid droplet on a solid surface, and the vapor–liquid surface tension of a fluid.

Numerical Investigation of Water Droplet Impact on Solid Surface in Microgravity

2013 ◽  
Vol 390 ◽  
pp. 65-70
Author(s):  
Jun Jun Tao ◽  
Jun Qin ◽  
Xue Han ◽  
Yong Ming Zhang
Keyword(s):  
Solid Surface ◽  
Water Droplet ◽  
Normal Gravity ◽  
Numerical Study ◽  
Liquid Droplet ◽  
Water Mist ◽  
Droplet Impact ◽  
Gravity Level ◽  
Vof Model ◽  
Fuel Vapour

A numerical study based on VOF model has been carried out to investigate the dynamics of water droplet impact on solid surface in microgravity in comparison with that in normal gravity to discuss the differences of the extinguishing mechanism of water mist in different gravity level. Water droplets with different initial diameters and impact velocities were considered. The simulated results show that the deformation process in microgravity lags behind that in normal gravity. And it was also found that Dmaxand spread velocities are smaller in microgravity as the potential energy decreases and the time taken for a liquid droplet to reach its maximum spread has no obvious regularity. Hence, the effect of cooling the fuel surface and diluting fuel vapour with water mist in microgravity may be not as good as that in normal gravity.The critical impact Weber number for water droplet breaking up in microgravity is lower than that in normal gravity as the reduction of the value of Bond number, which may result in diluting fuel vapour with water mist in microgravity being more effective than that in normal gravity in some case.

scholarly journals Is contact angle a cause or an effect? – A cautionary tale

2020 ◽  
Vol 146 ◽  
pp. 03004
Author(s):  
Douglas Ruth
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Two Dimensions ◽  
Experimental Results ◽  
Flow In Porous Media ◽  
Two Dimensional ◽  
Wide Range ◽  
Fluid Drop ◽  
Surrounding Fluid

The most influential parameter on the behavior of two-component flow in porous media is “wettability”. When wettability is being characterized, the most frequently used parameter is the “contact angle”. When a fluid-drop is placed on a solid surface, in the presence of a second, surrounding fluid, the fluid-fluid surface contacts the solid-surface at an angle that is typically measured through the fluid-drop. If this angle is less than 90°, the fluid in the drop is said to “wet” the surface. If this angle is greater than 90°, the surrounding fluid is said to “wet” the surface. This definition is universally accepted and appears to be scientifically justifiable, at least for a static situation where the solid surface is horizontal. Recently, this concept has been extended to characterize wettability in non-static situations using high-resolution, two-dimensional digital images of multi-component systems. Using simple thought experiments and published experimental results, many of them decades old, it will be demonstrated that contact angles are not primary parameters – their values depend on many other parameters. Using these arguments, it will be demonstrated that contact angles are not the cause of wettability behavior but the effect of wettability behavior and other parameters. The result of this is that the contact angle cannot be used as a primary indicator of wettability except in very restricted situations. Furthermore, it will be demonstrated that even for the simple case of a capillary interface in a vertical tube, attempting to use simply a two-dimensional image to determine the contact angle can result in a wide range of measured values. This observation is consistent with some published experimental results. It follows that contact angles measured in two-dimensions cannot be trusted to provide accurate values and these values should not be used to characterize the wettability of the system.

Hollow droplet impact on a solid surface

2021 ◽  
pp. 103740
Author(s):  
Mahdi Nasiri ◽  
Ghobad Amini ◽  
Christian Moreau ◽  
Ali Dolatabadi
Keyword(s):  
Solid Surface ◽  
Droplet Impact
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