Relationship between sliding acceleration of water droplets and dynamic contact angles on hydrophobic surfaces

2006 ◽  
Vol 600 (16) ◽  
pp. L204-L208 ◽  
Author(s):  
Munetoshi Sakai ◽  
Jeong-Hwan Song ◽  
Naoya Yoshida ◽  
Shunsuke Suzuki ◽  
Yoshikazu Kameshima ◽  
...  
Keyword(s):  
Dynamic Contact ◽  
Contact Angles ◽  
Water Droplets ◽  
Hydrophobic Surfaces

CONTROLLING THE MOVEMENT OF WATER DROPLETS WITH MICRO- AND HIERARCHICAL MICRO/NANOSTRUCTURES

2011 ◽  
Vol 18 (05) ◽  
pp. 209-222 ◽  
Author(s):  
TIINA RASILAINEN ◽  
ANNA KIRVESLAHTI ◽  
PAULIINA NEVALAINEN ◽  
MIKA SUVANTO ◽  
TAPANI A. PAKKANEN
Keyword(s):  
Injection Molding ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Middle Zone ◽  
Water Droplets ◽  
Hydrophobic Surfaces ◽  
Wetting Behavior

Anisotropic surfaces with micropillar- or micropillar/nanobump structures and anisotropic wetting behavior were fabricated. Structures were arranged as three parallel zones where the structure of the middle zone differed from that of the edge zones. The widths of the middle zones were increased systematically, and the effects of the middle zone structures and widths on the contact and sliding angles of water were investigated. Structures were fabricated on PP by injection molding. Microstructured mold inserts for injection molding were obtained by structuring aluminum foils with a microworking robot, and hierarchically structured mold inserts by anodizing the microstructured foils. It was possible to create surfaces where the microstructure in the middle zone was lower or higher than on the edges, or where the middle zone had only nanostructure or was unstructured. The behavior of water on the surfaces was characterized by measuring the dynamic contact angles and sliding angles parallel and perpendicular to the zones. Hydrophobic surfaces were achieved. With appropriate middle zone widths, clearly differing parallel and perpendicular contact angles were measured and elongation of droplets along the middle zones was detected.

Micro/Meso Scale Modelling of Two-Phase Flow on Functional Surfaces: A Numerical Simulation of Water Droplets on Natural Hydrophobic Surfaces With Micro Roughness

2009 ◽  
Author(s):  
Y. Y. Yan
Keyword(s):  
Two Phase Flow ◽  
Contact Angles ◽  
Phase Flow ◽  
Fluid Interface ◽  
Water Droplets ◽  
Hydrophobic Surfaces ◽  
Two Phase ◽  
Partial Wetting ◽  
Scale Modelling ◽  
Meso Scale

A micro/meso scale modelling of two-phase droplets move on hydrophilic/hydrophobic surfaces with micro roughness is reported. The physical model is basically of two-phase flow interacting with the surfaces of different hydrophobicity or wettability. Numerical modelling based on the lattice Boltzmann method (LBM) is developed and applied to the computational calculation and simulation. The LBM modelling deals with surface tension dominated behaviour of water droplets in air spreading on a hydrophilic surface with hydrophobic strips of different sizes and contact angles under different physical and interfacial conditions, and aims to find quantitative data and physical conditions of the biomimetic approaches. The current LBM can be applied to simulate two-phase fluids with large density ratio (up to 1000), and meanwhile deal with interactions between a fluid-fluid interface and a partial wetting wall. In the simulation, the interactions between the fluid-fluid interface and the partial wetting wall with different hydrophobic strips such as single strip, intersecting stripes, and alternating & parallel stripes, of different sizes and contact angles are considered and tested numerically; the phenomena of droplets spreading and breaking up, and the effect of hydrophobic strips on the surface wettability or self-cleaning characteristics are simulated, reported and discussed.

Computational Simulation of the Impact and Freezing of Micron-Size Water Droplets on Super-Hydrophobic Surfaces

2013 ◽  
Author(s):  
Mehdi Raessi ◽  
Miranda Thiele ◽  
Behrooz Amirzadeh
Keyword(s):  
Surface Temperature ◽  
Freezing Point ◽  
Computational Study ◽  
Computational Simulation ◽  
Contact Angles ◽  
Water Droplets ◽  
Hydrophobic Surfaces ◽  
Droplet Spreading ◽  
Micron Size ◽  
The Impact

We present a computational study on the dynamics and freezing of micron-size water droplets impinging onto super-hydrophobic surfaces, the temperatures of which are below the freezing point of water. Icing poses a great challenge for many industries. It is well known that increasing hydrophobicity can make a surface ice-phobic. Experiments show that millimeter size water drops landing on super-hydrophobic surfaces bounce off even when the surface temperature is well below the freezing point. However, it has been reported that the ice-phobicity feature of such surfaces can vanish due to frost formation on the surface, or when small micro-droplets begin to freeze and stick to the surface. Using an in-house, 3D, GPU-accelerated computational tool, we investigated the impact dynamics and freezing of a 40 μm water droplet impinging at 1.4 m/s onto two different super-hydrophobic surfaces chosen from [1]. The advancing and receding contact angles are 165° and 133°, respectively, on one surface, and 157° and 118°, respectively, on the other. The surface and initial droplet temperatures were varied from −25 to 25°C and from 0 to 25°C, respectively. On each surface a “transition” surface temperature was found, at which the drop behavior transitions from bouncing off the surface to sticking. The time between drop landing and bounce-off as well as the contact diameter between the stuck drop and the surface both increase with decreasing the surface temperature. The simulations also show that at some surface temperatures a thin ice layer forms during droplet spreading and then remelts as the droplet recoils.

Dynamic Contact Angles of Water Droplets Sliding on Inclined Hot Surfaces.

2000 ◽  
Vol 33 (1) ◽  
pp. 177-179 ◽  
Author(s):  
Jun Fukai ◽  
Masaharu Etou ◽  
Fumio Asanoma ◽  
Osamu Miyatake
Keyword(s):  
Dynamic Contact ◽  
Contact Angles ◽  
Water Droplets

Experimental study of dynamic contact angles on rough hydrophobic surfaces

2018 ◽  
Vol 513 ◽  
pp. 658-665 ◽  
Author(s):  
Alireza Mohammad Karim ◽  
Jonathan P. Rothstein ◽  
H. Pirouz Kavehpour
Keyword(s):  
Experimental Study ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Hydrophobic Surfaces

A novel method for measuring dynamic contact angles of fibers with spindle‐knots

2021 ◽  
Vol 138 (28) ◽  
Author(s):  
Maryam Aliabadi ◽  
Wilfried Konrad ◽  
Thomas Stegmaier ◽  
Volkmar Arnim ◽  
Cigdem Kaya ◽  
...  
Keyword(s):  
Dynamic Contact ◽  
Contact Angles ◽  
Novel Method

Wetting of Structured Hydrophobic Surfaces by Water Droplets

Langmuir ◽  
2005 ◽  
Vol 21 (26) ◽  
pp. 12235-12243 ◽  
Author(s):  
Oskar Werner ◽  
Lars Wågberg ◽  
Tom Lindström
Keyword(s):  
Water Droplets ◽  
Hydrophobic Surfaces
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