Superhydrophobic surface created by the silver mirror reaction and its drag-reduction effect on water

2009 ◽  
Vol 19 (20) ◽  
pp. 3301 ◽  
Author(s):  
Yali Zhou ◽  
Mei Li ◽  
Bin Su ◽  
Qinghua Lu
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Silver Mirror ◽  
Reduction Effect ◽  
Silver Mirror Reaction

scholarly journals Noise Reduction Effect of Superhydrophobic Surfaces with Streamwise Strip of Channel Flow

2021 ◽  
Vol 11 (9) ◽  
pp. 3869
Author(s):  
Chen Niu ◽  
Yongwei Liu ◽  
Dejiang Shang ◽  
Chao Zhang
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Noise Reduction ◽  
Channel Flow ◽  
Superhydrophobic Surface ◽  
Sound Field ◽  
Flow Noise ◽  
Slip Boundary ◽  
Eddy Simulation ◽  
Reduction Effect

Superhydrophobic surface is a promising technology, but the effect of superhydrophobic surface on flow noise is still unclear. Therefore, we used alternating free-slip and no-slip boundary conditions to study the flow noise of superhydrophobic channel flows with streamwise strips. The numerical calculations of the flow and the sound field have been carried out by the methods of large eddy simulation (LES) and Lighthill analogy, respectively. Under a constant pressure gradient (CPG) condition, the average Reynolds number and the friction Reynolds number are approximately set to 4200 and 180, respectively. The influence on noise of different gas fractions (GF) and strip number in a spanwise period on channel flow have been studied. Our results show that the superhydrophobic surface has noise reduction effect in some cases. Under CPG conditions, the increase in GF increases the bulk velocity and weakens the noise reduction effect. Otherwise, the increase in strip number enhances the lateral energy exchange of the superhydrophobic surface, and results in more transverse vortices and attenuates the noise reduction effect. In our results, the best noise reduction effect is obtained as 10.7 dB under the scenario of the strip number is 4 and GF is 0.5. The best drag reduction effect is 32%, and the result is obtained under the scenario of GF is 0.8 and strip number is 1. In summary, the choice of GF and the number of strips is comprehensively considered to guarantee the performance of drag reduction and noise reduction in this work.

scholarly journals Fabrication of superhydrophobic surface by oxidation growth of flower-like nanostructure on a steel foil

RSC Advances ◽  
2017 ◽  
Vol 7 (41) ◽  
pp. 25341-25346 ◽  
Author(s):  
Rui Weng ◽  
Haifeng Zhang ◽  
Liang Yin ◽  
Wanting Rong ◽  
Zhiwen Wu ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Novel Method ◽  
Reduction Effect ◽  
Oxidation Growth

A novel method to fabricate the superhydrophobic surface with a 3D flower-like micro-nanostructure on the steel foil was presented here. The surface shows good drag reduction effect and has numerous technical applications in drag reduction field.

scholarly journals Fabrication of Zinc Substrate Encapsulated by Fluoropolyurethane and Its Drag-Reduction Enhancement by Chemical Etching

Coatings ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 377 ◽  
Author(s):  
Yuanzhe Li ◽  
Zhe Cui ◽  
Qiucheng Zhu ◽  
Srikanth Narasimalu ◽  
Zhili Dong
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Chemical Etching ◽  
Flow Resistance ◽  
Reduction Rate ◽  
Low Flow ◽  
Rolling Angle ◽  
Standard Design ◽  
Reduction Effect ◽  
Nanoscale Roughness

A fluoropolyurethane-encapsulated process was designed to rapidly fabricate low-flow resistance surfaces on the zinc substrate. For the further enhancement of the drag-reduction effect, Cu2+-assisted chemical etching was introduced during the fabrication process, and its surface morphology, wettability, and flow-resistance properties in a microchannel were also studied. It is indicated that the zinc substrate with a micro-nanoscale roughness obtained by Cu2+-assisted nitric acid etching was superhydrophilic. However, after the etched zinc substrate is encapsulated with fluoropolyurethane, the superhydrophobic wettability can be obtained with a contact angle of 154.8° ± 2.5° and a rolling angle of less than 10°. As this newly fabricated surface was placed into a non-standard design microchannel, it was found that with the increase of Reynolds number, the drag-reduction rate of the superhydrophobic surface remained basically unchanged at 4.0% compared with the original zinc substrate. Furthermore, the prepared superhydrophobic surfaces exhibited outstanding reliability in most liquids.

Experimental study on the drag reduction effect of a rotating superhydrophobic surface in micro gap flow field

2016 ◽  
Vol 23 (8) ◽  
pp. 3033-3040 ◽  
Author(s):  
Chunze Wang ◽  
Fei Tang ◽  
Pengfei Hao ◽  
Qi Li ◽  
Xiaohao Wang
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Gap Flow ◽  
Reduction Effect

Drag reduction effect of ultraviolet laser-fabricated superhydrophobic surface

2019 ◽  
Vol 36 (12) ◽  
pp. 1307-1314 ◽  
Author(s):  
Xiuju Zhao ◽  
Yao Xue ◽  
Huan Yang ◽  
Wei Xue ◽  
Fengping Li ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Superhydrophobic Surface ◽  
Ultraviolet Laser ◽  
Reduction Effect

Effects of the air layer of an idealized superhydrophobic surface on the slip length and skin-friction drag

2016 ◽  
Vol 790 ◽  
Author(s):  
Taeyong Jung ◽  
Haecheon Choi ◽  
John Kim
Keyword(s):  
Drag Reduction ◽  
Skin Friction ◽  
Superhydrophobic Surface ◽  
Slip Length ◽  
Joint Probability ◽  
Turbulent Channel Flow ◽  
Water Interface ◽  
Friction Drag ◽  
Recirculating Flow ◽  
Air Water Interface

The anisotropy of the slip length and its effect on the skin-friction drag are numerically investigated for a turbulent channel flow with an idealized superhydrophobic surface having an air layer, where the idealized air–water interface is flat and does not contain the surface-tension effect. Inside the air layer, both the shear-driven flow and recirculating flow with zero net mass flow rate are considered. With increasing air-layer thickness, the slip length, slip velocity and percentage of drag reduction increase. It is shown that the slip length is independent of the water flow and depends only on the air-layer geometry. The amount of drag reduction obtained is in between those by the empirical formulae from the streamwise slip only and isotropic slip, indicating that the present air–water interface generates an anisotropic slip, and the streamwise slip length ($b_{x}$) is larger than the spanwise one ($b_{z}$). From the joint probability density function of the slip velocities and velocity gradients at the interface, we confirm the anisotropy of the slip lengths and obtain their relative magnitude ($b_{x}/b_{z}=4$) for the present idealized superhydrophobic surface. It is also shown that the Navier slip model is valid only in the mean sense, and it is generally not applicable to fluctuating quantities.

Silver mirror reaction metallized chromatography paper for supercapacitor application

2021 ◽  
Author(s):  
I-Hsuan Chen ◽  
Jung-Hsien Chang ◽  
Ren-Jie Xie ◽  
Chia-Hui Tseng ◽  
Sheng-Rong Hsieh ◽  
...  
Keyword(s):  
Flexible Electronics ◽  
Photoelectron Spectroscopy ◽  
Cost Effective ◽  
Water Contact ◽  
X Ray ◽  
Supercapacitor Application ◽  
Resource Limited ◽  
Vis Spectroscopy ◽  
Silver Mirror ◽  
Silver Mirror Reaction

Abstract In this study, the easy-to-operate silver mirror reaction (SMR) was used for metallizing chromatography paper. The SMR-metallized paper was characterized by water contact angle measurements, a surface profiler, X-ray photoelectron spectroscopy, UV-vis spectroscopy, X-ray diffraction, and electrical resistance measurement. The characterization results show that Ag was successfully synthesized on cellulose fibers and was electrically conductive after cyclic bending. Moreover, this SMR-metallized paper was used as electrodes for fabricating a supercapacitor. This SMR-metallized paper could be used for realizing cost-effective flexible electronics applied in on-site biochemical sensing in resource-limited settings.

Numerical study on the mechanism of drag reduction for interceptors on planning boats

2021 ◽  
Author(s):  
Lianzheng Cui ◽  
Zuogang Chen ◽  
Yukun Feng
Keyword(s):  
Drag Reduction ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Numerical Study ◽  
Dynamic Pressure ◽  
Motion Model ◽  
Gauge Pressure ◽  
Reduction Effect ◽  
Pressure Resistance ◽  
Viscous Pressure

The drag reduction effect of interceptors on planning boats has been widely proven, but the mechanism of the effect has been rarely studied in terms of drag components, especially for spray resistance. The resistance was caused by the high gauge pressure under the boats transformed from the dynamic pressure, and it is the largest drag component in the high-speed planning mode. In this study, numerical simulations of viscous flow fields around a planning boat with and without interceptors were conducted. A two degrees of freedom motion model was employed to simulate the trim and sinkage. The numerical results were validated against the experimental data. The flow details with and without the interceptor were visualized and compared to reveal the underlying physics. A thinner and longer waterline could be achieved by the interceptor, which made the boat push the water away more gradually, and hence, the wave-making resistance could be decreased. The improved waterline also reduced the component of the freestream normal to the hull surface and led to the less transformed dynamic pressure, resulting in the lowAer spray resistance. Furthermore, the suppression of the flow separation could also be benefited from the interceptor; the viscous pressure resistance was therefore decreased.

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