scholarly journals Comment on “Approaching the theoretical contact time of a bouncing droplet on the rational macrostructured superhydrophobic surfaces” [Appl. Phys. Lett. 107, 111604 (2015)]

2016 ◽  
Vol 108 (1) ◽  
pp. 016101 ◽  
Author(s):  
Visakh Vaikuntanathan
Keyword(s):  
Contact Time ◽  
Superhydrophobic Surfaces

scholarly journals Drops bouncing off macro-textured superhydrophobic surfaces

2017 ◽  
Vol 824 ◽  
pp. 866-885 ◽  
Author(s):  
Ali Mazloomi Moqaddam ◽  
Shyam S. Chikatamarla ◽  
Iliya V. Karlin
Keyword(s):  
Contact Time ◽  
Numerical Study ◽  
Three Dimensional ◽  
Superhydrophobic Surfaces ◽  
Nonlinear Behaviour ◽  
Textured Surfaces ◽  
Texture Density ◽  
Wide Range ◽  
Quantitative Manner ◽  
The Impact

Recent experiments with droplets impacting macro-textured superhydrophobic surfaces revealed new regimes of bouncing with a remarkable reduction of the contact time. Here we present a comprehensive numerical study that reveals the physics behind these new bouncing regimes and quantifies the roles played by various external and internal forces. For the first time, accurate three-dimensional simulations involving realistic macro-textured surfaces are performed. After demonstrating that simulations reproduce experiments in a quantitative manner, the study is focused on analysing the flow situations beyond current experiments. We show that the experimentally observed reduction of contact time extends to higher Weber numbers, and analyse the role played by the texture density. Moreover, we report a nonlinear behaviour of the contact time with the increase of the Weber number for imperfectly coated textures, and study the impact on tilted surfaces in a wide range of Weber numbers. Finally, we present novel energy analysis techniques that elaborate and quantify the interplay between the kinetic and surface energy, and the role played by the dissipation for various Weber numbers.

scholarly journals Reducing the contact time using macro anisotropic superhydrophobic surfaces — effect of parallel wire spacing on the drop impact

2017 ◽  
Vol 9 (8) ◽  
pp. e415-e415 ◽  
Author(s):  
Meirong Song ◽  
Zhaohui Liu ◽  
Yongjian Ma ◽  
Zhichao Dong ◽  
Yilin Wang ◽  
...  
Keyword(s):  
Contact Time ◽  
Drop Impact ◽  
Superhydrophobic Surfaces ◽  
Parallel Wire

Springboard Droplet Bouncing on Flexible Superhydrophobic Substrates

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Patricia B. Weisensee ◽  
Junjiao Tian ◽  
Nenad Miljkovic ◽  
William P. King
Keyword(s):  
Natural Frequency ◽  
Contact Time ◽  
High Speed ◽  
Flexible Substrate ◽  
Superhydrophobic Surfaces ◽  
High Speed Imaging ◽  
Impact Speed ◽  
Lift Off ◽  
The Impact ◽  
Maximum Spreading

Droplet impact on rigid, superhydrophobic surfaces follows the well-known spreading, recoil, and lift-off behavior at lower impact speeds (a), and splashing at higher impact speeds (b). The contact time tc of these bouncing droplets is independent of the impact speed, and difficult to control. Using high speed imaging (9500 fps) of water droplets impacting superhydrophobic substrates with stiffness 0.5 to 7630 N/m (rigid), we were able to show that substrate flexibility can reduce contact times. Upon impact on a flexible substrate, the droplet excites the substrate to oscillate at the membrane or cantilever natural frequency (d). The oscillation accelerates the droplet upwards, initiating early droplet lift-off at the edges of the droplet close to the point of maximum spreading (c). Droplets fully lift off before fully recoiling, i.e. in a pancake shape. We call this phenomenon the springboard effect. Contact times are reduced by up to 50% compared to rigid substrates.

scholarly journals Bouncing Dynamics of Impact Droplets on the Biomimetic Plane and Convex Superhydrophobic Surfaces with Dual-Level and Three-Level Structures

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1524
Author(s):  
Zhongxu Lian ◽  
Jinkai Xu ◽  
Wanfei Ren ◽  
Zuobin Wang ◽  
Huadong Yu
Keyword(s):  
Contact Time ◽  
Superhydrophobic Surface ◽  
Electrical Discharge Machining ◽  
Structural Parameters ◽  
Level Structure ◽  
Solid Surfaces ◽  
Superhydrophobic Surfaces ◽  
Convex Surfaces ◽  
Superhydrophobic Property ◽  
Water Drops

Reducing the contact time of a water droplet on non-wetting surfaces has great potential in the areas of self-cleaning and anti-icing, and gradually develops into a hot issue in the field of wettability surfaces. However, the existing literature on dynamic behavior of water drops impacting on superhydrophobic surfaces with various structural shapes is insufficient. Inspired by the microstructure of lotus leaf and rice leaf, dual-level and three-level structures on plane and convex surfaces were successfully fabricated by wire electrical discharge machining on aluminum alloy. After spraying hydrophobic nanoparticles on the surfaces, the plane and convex surfaces with dual-level and three-level structures showed good superhydrophobic property. Bouncing dynamics of impact droplets on the superhydrophobic surfaces wereinvestigated, and the results indicated that the contact time of plane superhydrophobic surface with a three-level structure was minimal, which is 60.4% less than the plane superhydrophobic surface with dual-level structure. The effect of the interval S, width D, and height H of the structure on the plane superhydrophobic surface with three-level structure on contact time was evaluated to obtain the best structural parameters for reducing contact time. This research is believed to guide the direction of the structural design of the droplet impinging on solid surfaces.

Contact time on curved superhydrophobic surfaces

2020 ◽  
Vol 101 (4) ◽  
Author(s):  
Jeonghoon Han ◽  
Wonjung Kim ◽  
Changwoo Bae ◽  
Dongwook Lee ◽  
Seungwon Shin ◽  
...  
Keyword(s):  
Contact Time ◽  
Superhydrophobic Surfaces

Contact time on inclined superhydrophobic surfaces decorated with parallel macro-ridges

2020 ◽  
Vol 599 ◽  
pp. 124924 ◽  
Author(s):  
Dian-Ji Lin ◽  
Ling-Zhe Zhang ◽  
Meng-Chao Yi ◽  
Shu-Rong Gao ◽  
Yan-Ru Yang ◽  
...  
Keyword(s):  
Contact Time ◽  
Superhydrophobic Surfaces

Approaching the theoretical contact time of a bouncing droplet on the rational macrostructured superhydrophobic surfaces

2015 ◽  
Vol 107 (11) ◽  
pp. 111604 ◽  
Author(s):  
Y. Shen ◽  
J. Tao ◽  
H. Tao ◽  
S. Chen ◽  
L. Pan ◽  
...  
Keyword(s):  
Contact Time ◽  
Superhydrophobic Surfaces

scholarly journals Contact Time of Double-Droplet Impacting Superhydrophobic Surfaces with Different Macrotextures

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 896
Author(s):  
Dian-Ji Lin ◽  
Ling-Zhe Zhang ◽  
Meng-Chao Yi ◽  
Xin Wang ◽  
Shu-Rong Gao ◽  
...  
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Contact Time ◽  
Superhydrophobic Surface ◽  
Vertical Wall ◽  
Spray Cooling ◽  
Superhydrophobic Surfaces ◽  
Geometrical Parameters ◽  
Boltzmann Method ◽  
Center Distance

The contact time of droplets on superhydrophobic surfaces is an especially important parameter in many applications, such as self-cleaning, anti-icing, and spray cooling. In this study, we investigate the contact time of two identical droplets simultaneously impacting superhydrophobic surfaces decorated with three different macrotextures, i.e., bathtub-like groove (S1), vertical wall (S2), and rectangular ridge (S3), via lattice Boltzmann method (LBM) simulations. We explore influences of the geometrical parameters of the macrotextures, as well as the center-to-center distance of the two droplets, on the contact time. We found a new rebounding regime with significantly reduced contact times. We demonstrate that, as compared with impacting a smooth superhydrophobic surface, the contact time can be decreased by 41% for macrotexture S1 because of the asymmetric spreading and retraction of droplets motivated by the macrotexture. We also demonstrate that the new regime depends on the center-to-center distance and geometrical parameters of the macrotextures.

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