Experimental drag reduction study of super-hydrophobic surface with dual-scale structures

2013 ◽  
Vol 286 ◽  
pp. 206-211 ◽  
Author(s):  
Sungnam Lyu ◽  
Dang C. Nguyen ◽  
Dongseob Kim ◽  
Woonbong Hwang ◽  
Bumsang Yoon
Keyword(s):  
Drag Reduction ◽  
Hydrophobic Surface ◽  
Scale Structures ◽  
Dual Scale

Wrinkled, Dual-Scale Structures of Diamond-Like Carbon (DLC) for Superhydrophobicity

Langmuir ◽  
2010 ◽  
Vol 26 (1) ◽  
pp. 484-491 ◽  
Author(s):  
Yudi Rahmawan ◽  
Myoung-Woon Moon ◽  
Kyung-Suk Kim ◽  
Kwang-Ryeol Lee ◽  
Kahp-Yang Suh
Keyword(s):  
Diamond Like Carbon ◽  
Scale Structures ◽  
Dual Scale

Fabrication of a Robust Superhydrophobic Ni Coating with Micro–Nano Dual‐Scale Structures on 316L Stainless Steel

2020 ◽  
pp. 2000913
Author(s):  
Enyang Liu ◽  
Liyuan Wang ◽  
Xiaoli Yin ◽  
Jinhui Hu ◽  
Sirong Yu ◽  
...  
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Scale Structures ◽  
Dual Scale

Numerical Simulation of Fluid Slip at a Hydrophobic Surface

Volume 4 ◽  
2004 ◽  
Author(s):  
Takao Fujita ◽  
Keizo Watanabe
Keyword(s):  
Boundary Condition ◽  
Laminar Flow ◽  
Circular Cylinder ◽  
Drag Reduction ◽  
Hydrophobic Surface ◽  
Friction Reduction ◽  
Water Repellent ◽  
Two Dimensional ◽  
Hydrophobic Property ◽  
Flow Past

Laminar drag reduction is achieved by using a hydrophobic surface. In this method, fluid slip is applied at the hydrophobic surface. An initial experiment to clarify for a laminar skin friction reduction was conducted using ducts with a highly water-repellent surface. The surface has a fractal-type structure with many fine grooves. Fluid slip at a hydrophobic surface has been analyzed by applying a new wet boundary condition. In this simulation, an internal flow is assumed to be a two-dimensional laminar flow in a rectangular duct and an external flow is assumed to be a two-dimensional laminar flow past a circular cylinder. The VOF technique has been used as the method for tracking gas-liquid interfaces, and the CSF model has been used as the method for modeling surface tension effects. The wet boundary condition for the hydrophobic property on the surface has been determined from the volume ratio in contact with water near the surface. The model with a stable gas-liquid interface and the experimental results of flow past a circular cylinder at Re = 250 without growing the Karman vortex street are made, and these results show that laminar drag reduction occurring due to fluid slip can be explained in this model.

scholarly journals Ultra-Low-Reflective, Self-Cleaning Surface by Fabrication Dual-Scale Hierarchical Optical Structures on Silicon

Coatings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1541
Author(s):  
Miaomiao Duan ◽  
Jingjun Wu ◽  
Yubin Zhang ◽  
Ning Zhang ◽  
Jun Chen ◽  
...  
Keyword(s):  
Incident Light ◽  
Fdtd Method ◽  
Silicon Substrates ◽  
Light Emitting ◽  
Reflective Surface ◽  
Silicon Devices ◽  
Scale Structures ◽  
Self Cleaning ◽  
Difference Time ◽  
Dual Scale

An integrated functional anti-reflective surface is of great significance for optical and optoelectronic devices. Hence, its preparation has attracted great attention from many researchers. This study combined wet alkaline etching approaches and reactive ion etching (RIE) techniques to create a dual-scale hierarchical anti-reflective surface on silicon substrates. The effect of RIE time on surface morphology and optical performance was investigated using multiple characterization forms. The optimal parameters for the fabrication of dual-scale structures by the composite etching process were explored. The silicon surface with a dual-scale structure indicated excellent anti-reflective properties (minimum reflectivity of 0.9%) in the 300 to 1100 nm wavelength range. In addition, the ultra-low reflection characteristic of the surface remained prominent at incident light angles up to 60°. The simulated spectra using the finite difference time domain (FDTD) method agreed with the experimental results. Superhydrophobicity and self-cleaning were also attractive properties of the surface. The functionally integrated surface enables silicon devices to have broad application prospects in solar cells, light emitting diodes (LEDs), photoelectric detectors, and outdoor equipment.

Drag Reduction on Microscale Concave-Convex Surface

1999 ◽  
Author(s):  
Masato Hasegawa ◽  
Hideki Nariai ◽  
Kazufumi Kaneko ◽  
Hiroshi Maki ◽  
Akira Yabe ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Friction Coefficient ◽  
Drag Reduction ◽  
Convex Surface ◽  
Hydrophobic Surface ◽  
Frictional Torque ◽  
Small Scale ◽  
Water Repellent ◽  
Hydrophobic Coating ◽  
Gas Layer

Abstract Experimental work on the drag reduction phenomena on the highly water-repellent wall has been done. Fabricated surface, which has concave-convex structure of micrometer scale, was implemented as the tested plate in cone-plate viscometer. The surfaces exhibited the increase of the frictional torque with the projection height of 5 μm. The case of 1.15μm did not show the increase of flow resistance while the result of case of 1.4μm depended on Reynolds number. Another set of the ultra small-scale concave-convex surface was made on 4 inches silicon wafer by lithography and RIE (Reactive Ion Etching), with hydrophobic coating. The surface with high contact angle of 150 degrees for water droplet of 1.4mm diameter showed the drag reduction by maximally 9 percent at Reynolds number around 6.5 × 104. The hydrophobic surface exhibited the decrease in friction coefficient by 6 percent even when it was smooth. PTFE membrane filters have also been tested since the filters can trap gas or bubble on surface, considering that the existence of gas layer at solid liquid interlace is necessary for slip at the boundary to be occurred. The filters showed reduction in friction coefficient, maximally about 6 percent. The rate of the reduction slightly changes related to the size of pores in the filters.

Creation of a superhydrophobic surface from a sublimed smectic liquid crystal

RSC Advances ◽  
2014 ◽  
Vol 4 (51) ◽  
pp. 26946-26950 ◽  
Author(s):  
Dae Seok Kim ◽  
Yun Jeong Cha ◽  
Hanim Kim ◽  
Mun Ho Kim ◽  
Yun Ho Kim ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Superhydrophobic Surface ◽  
Smectic Liquid Crystals ◽  
Smectic Liquid Crystal ◽  
Scale Structures ◽  
Dual Scale

Dual-scale structures showing superhydrophobic characteristics have been fabricated using sublimable smectic liquid crystals.

Wideband anti-reflective micro/nano dual-scale structures: fabrication and optical properties

2011 ◽  
Vol 6 (11) ◽  
pp. 947 ◽  
Author(s):  
Xiaosheng Zhang ◽  
Qianli Di ◽  
Fuyun Zhu ◽  
Guangyi Sun ◽  
Haixia Zhang
Keyword(s):  
Optical Properties ◽  
Scale Structures ◽  
Dual Scale
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