Critical sliding angle of water droplet on parallel hydrophobic grooved surface

2020 ◽  
Vol 585 ◽  
pp. 124083 ◽  
Author(s):  
Yi Ding ◽  
Li Jia ◽  
Qi Peng ◽  
Jian Guo
Keyword(s):  
Water Droplet ◽  
Sliding Angle ◽  
Grooved Surface

scholarly journals Inner surface of Nepenthes slippery zone: ratchet effect of lunate cells causes anisotropic superhydrophobicity

2020 ◽  
Vol 7 (3) ◽  
pp. 200066
Author(s):  
Lixin Wang ◽  
Shuoyan Zhang ◽  
Shanshan Li ◽  
Shixing Yan ◽  
Shiyun Dong
Keyword(s):  
Water Droplet ◽  
Angle Measurement ◽  
Dense Layer ◽  
Ultrapure Water ◽  
Ratchet Effect ◽  
Sliding Angle ◽  
Static Contact ◽  
Inner Surface ◽  
Structure Observation ◽  
Different Order

Inner surface of Nepenthes slippery zone shows anisotropic superhydrophobic wettability. Here, we investigate what factors cause the anisotropy via sliding angle measurement, morphology/structure observation and model analysis. Static contact angle of ultrapure-water droplet exhibits the value of 154.80°–156.83°, and sliding angle towards pitcher bottom and up is 2.82 ± 0.45° and 5.22 ± 0.28°, respectively. The slippery zone under investigation is covered by plenty of lunate cells with both ends bending downward, and a dense layer of wax coverings without directional difference in morphology/structure. Results indicate that the slippery zone has a considerable anisotropy in superhydrophobic wettability that is most likely caused by the lunate cells. A model was proposed to quantitatively analyse how the structure characteristics of lunate cells affect the anisotropic superhydrophobicity, and found that the slope/precipice structure of lunate cells forms a ratchet effect to cause ultrapure-water droplet to roll towards pitcher bottom/up in different order of difficulty. Our investigation firstly reveals the mechanism of anisotropic superhydrophobic wettability of Nepenthes slippery zone, and inspires the bionic design of superhydrophobic surfaces with anisotropic properties.

Effects of Grooved Surface with Nano-Ridges on Amplification of Hydrophobic Property

2013 ◽  
Vol 684 ◽  
pp. 26-31 ◽  
Author(s):  
Dong Ki Lee ◽  
Jun Hyung Lee ◽  
Young Hak Cho
Keyword(s):  
Silicon Wafer ◽  
Chemical Treatment ◽  
Water Droplet ◽  
Contact Angles ◽  
Groove Width ◽  
Self Assembled Monolayers ◽  
Hydrophobic Property ◽  
Chemical Treatments ◽  
Assembled Monolayers ◽  
Grooved Surface

This paper shows how much the size of groove and ridge, which were fabricated on the silicon wafer, affected on the hydrophobicity of the grooved surface without chemical treatments and with chemical treatment such as self-assembled monolayers (SAMs) of organic silane. Furthermore, the contact angles (CAs) of water droplet on specimens were measured and compared with theoretical CAs of droplet in Cassie-Baxter state. The experimental results indicated that the specimen with the extensive groove width had super-hydrophobicity as compared to the specimen with relatively narrow groove width. The highest CAs of chemically non-treated specimens and chemically treated specimens were 171.9˚ and 173.1˚. This work explains that the grooved surface with nano-ridges and SAM coating contributes to improve hydrophobicity of surface.

scholarly journals Behavior of Sliding Angle as Function of Temperature Difference between Droplet and Superhydrophobic Coating for Aircraft Ice Protection Systems

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 219
Author(s):  
Mitsugu Hasegawa ◽  
Haruka Endo ◽  
Katsuaki Morita ◽  
Hirotaka Sakaue ◽  
Shigeo Kimura
Keyword(s):  
Temperature Difference ◽  
Water Droplet ◽  
Superhydrophobic Coating ◽  
Aircraft Icing ◽  
Sliding Angle ◽  
Scientific Question ◽  
Coating Surface ◽  
Protection Systems ◽  
Active Research ◽  
Interaction Surface

A hybrid anti-/de-icing system combining a superhydrophobic coating and an electrothermal heater is an area of active research for aircraft icing prevention. The heater increases the temperature of the interaction surface between impinging droplets and an aircraft surface. One scientific question that has not been studied in great detail is whether the temperatures of the droplet and the surface or the temperature difference between the two dominate the anti-/de-icing performance. Herein, this scientific question is experimentally studied based on the mobility of a water droplet over a superhydrophobic coating. The mobility is characterized by the sliding angle between the droplet and the coating surface. It was found that the temperature difference between the droplet and the coating surface has a higher impact on the sliding angle than their individual temperatures.

Spreading and Deposition Characteristics of a Water Droplet Impacting on Hydrophobic Textured Surfaces

2012 ◽  
Vol 17 (1) ◽  
pp. 14-19
Author(s):  
Jae-Bong Lee ◽  
Joo-Hyun Moon ◽  
Seong-Hyuk Lee
Keyword(s):  
Water Droplet ◽  
Textured Surfaces

EVAPORATION OF SINGLE WATER DROPLET UNDER LASER IRRADIATION

2018 ◽  
Author(s):  
Pei Zhang ◽  
Chuang Sun ◽  
Fengxian Sun ◽  
Zicheng Jin
Keyword(s):  
Laser Irradiation ◽  
Water Droplet

IMPROVED LUMPED-DIFFERENTIAL ANALYSIS OF THE FREEZING PROCESS IN A SUPERCOOLED WATER DROPLET

2020 ◽  
Author(s):  
Emerson Barbosa dos Anjos ◽  
Carolina Palma Naveira Cotta ◽  
Renato Machado Cotta ◽  
Igor Soares Carvalho ◽  
Manish Tiwari
Keyword(s):  
Water Droplet ◽  
Supercooled Water ◽  
Freezing Process ◽  
Differential Analysis

Case study: Theoretical calculation model and variable condition analysis research on the water-splashing noise for natural draft wet cooling towers

2020 ◽  
Vol 68 (2) ◽  
pp. 137-145
Author(s):  
Yang Zhouo ◽  
Ming Gao ◽  
Suoying He ◽  
Yuetao Shi ◽  
Fengzhong Sun
Keyword(s):  
Theoretical Model ◽  
Sound Pressure Level ◽  
Water Droplet ◽  
Water Distribution ◽  
Sound Pressure ◽  
Cooling Tower ◽  
Distribution Patterns ◽  
Calculation Model ◽  
Pressure Level ◽  
Cooling Towers

Based on the basic theory of water droplets impact noise, the generation mechanism and calculation model of the water-splashing noise for natural draft wet cooling towers were established in this study, and then by means of the custom software, the water-splashing noise was studied under different water droplet diameters and water-spraying densities as well as partition water distribution patterns conditions. Comparedwith the water-splashing noise of the field test, the average difference of the theoretical and the measured value is 0.82 dB, which validates the accuracy of the established theoretical model. The results based on theoretical model showed that, when the water droplet diameters are smaller in cooling tower, the attenuation of total sound pressure level of the water-splashing noise is greater. From 0 m to 8 m away from the cooling tower, the sound pressure level of the watersplashing noise of 3 mm and 6 mm water droplets decreases by 8.20 dB and 4.36 dB, respectively. Additionally, when the water-spraying density becomes twice of the designed value, the sound pressure level of water-splashing noise all increases by 3.01 dB for the cooling towers of 300 MW, 600 MW and 1000 MW units. Finally, under the partition water distribution patterns, the change of the sound pressure level is small. For the R s/2 and Rs/3 partition radius (Rs is the radius of water-spraying area), when the water-spraying density ratio between the outer and inner zone increases from 1 to 3, the sound pressure level of water-splashing noise increases by 0.7 dB and 0.3 dB, respectively.

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