scholarly journals Dynamic Behaviors and Energy Transition Mechanism of Droplets Impacting on Hydrophobic Surfaces

2016 ◽  
Vol 2016 ◽  
pp. 1-9
Author(s):  
Qiaogao Huang ◽  
Ya Zhang ◽  
Guang Pan
Keyword(s):  
Contact Angle ◽  
Kinetic Energy ◽  
Surface Hydrophobicity ◽  
Solid Surfaces ◽  
Gravitational Potential Energy ◽  
Hydrophobic Surfaces ◽  
Dynamic Behaviors ◽  
Transition Mechanism ◽  
Rebound Phenomenon ◽  
Intrinsic Contact Angle

The wettability of hydrophobic surfaces and the dynamic behaviors of droplets impacting on hydrophobic surfaces are simulated using a lattice Boltzmann method, and the condition for the rebound phenomenon of droplets impacting on solid surfaces is analyzed. The results show that there is a linear relationship between the intrinsic contact angle and the interaction strength of fluid-wall particles. For hydrophobic surfaces with the same intrinsic contact angle, the micromorphology can increase the surface hydrophobicity, especially the hierarchical micromorphology. The dynamic behaviors of droplets impacting on solid surfaces are affected by the wettability. The surface hydrophobicity is stronger, and the rebound phenomenon occurs easier. If the droplet’s kinetic energy is greater than the sum of the surface energy and the minimum conversion gravitational potential energy when the spreading and shrinking finish, the rebound phenomenon will occur. As the hydrophobic surface’s viscous dissipation is much smaller than the hydrophilic surface’s, the droplet still has high kinetic energy after the spreading and shrinking, which is advantageous to rebound for droplets.

Tracker-assisted modelling: simultaneous validation of the conservation law of energy and the work-energy theorem

2021 ◽  
Vol 57 (1) ◽  
pp. 015012
Author(s):  
Unofre B Pili ◽  
Renante R Violanda
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Conservation Law ◽  
Gravitational Potential Energy ◽  
Time Data ◽  
Home Based ◽  
Basic Physics ◽  
Free Falling ◽  
Work Done

Abstract The video of a free-falling object was analysed in Tracker in order to extract the position and time data. On the basis of these data, the velocity, gravitational potential energy, kinetic energy, and the work done by gravity were obtained. These led to a rather simultaneous validation of the conservation law of energy and the work–energy theorem. The superimposed plots of the kinetic energy, gravitational potential energy, and the total energy as respective functions of time and position demonstrate energy conservation quite well. The same results were observed from the plots of the potential energy against the kinetic energy. On the other hand, the work–energy theorem has emerged from the plot of the total work-done against the change in kinetic energy. Because of the accessibility of the setup, the current work is seen as suitable for a home-based activity, during these times of the pandemic in particular in which online learning has remained to be the format in some countries. With the guidance of a teacher, online or face-to-face, students in their junior or senior high school—as well as for those who are enrolled in basic physics in college—will be able to benefit from this work.

scholarly journals Walking in simulated reduced gravity: mechanical energy fluctuations and exchange

1999 ◽  
Vol 86 (1) ◽  
pp. 383-390 ◽  
Author(s):  
Timothy M. Griffin ◽  
Neil A. Tolani ◽  
Rodger Kram
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Gravitational Potential Energy ◽  
Reduced Gravity

Walking humans conserve mechanical and, presumably, metabolic energy with an inverted pendulum-like exchange of gravitational potential energy and horizontal kinetic energy. Walking in simulated reduced gravity involves a relatively high metabolic cost, suggesting that the inverted-pendulum mechanism is disrupted because of a mismatch of potential and kinetic energy. We tested this hypothesis by measuring the fluctuations and exchange of mechanical energy of the center of mass at different combinations of velocity and simulated reduced gravity. Subjects walked with smaller fluctuations in horizontal velocity in lower gravity, such that the ratio of horizontal kinetic to gravitational potential energy fluctuations remained constant over a fourfold change in gravity. The amount of exchange, or percent recovery, at 1.00 m/s was not significantly different at 1.00, 0.75, and 0.50 G (average 64.4%), although it decreased to 48% at 0.25 G. As a result, the amount of work performed on the center of mass does not explain the relatively high metabolic cost of walking in simulated reduced gravity.

Preparation of Super Hydrophobic Surfaces by the Stainless Steel Wire Mesh as Templates

2012 ◽  
Vol 562-564 ◽  
pp. 56-59 ◽  
Author(s):  
Jian Zhuang ◽  
Meng Meng Du ◽  
Heng Zhi Cai ◽  
Ya Jun Zhang ◽  
Da Ming Wu
Keyword(s):  
Contact Angle ◽  
Stainless Steel ◽  
Steel Wire ◽  
Contact Angles ◽  
Wire Mesh ◽  
Stainless Steel Wire ◽  
Hydrophobic Surfaces ◽  
Water Contact ◽  
Stainless Steel Wire Mesh ◽  
Steel Wire Mesh

A facile method for manufacturing super hydrophobic surfaces is presented using the stainless steel wire mesh as templates. The rough surfaces of polymers including polycarbonate, polypropylene and PMMA are prepared with hot embossing on different specifications of stainless steel wire mesh. Scanning electron microscopy (SEM) results reveal that the surfaces roughness of the polymers can be controlled by selecting templates. Contact angle measurement shows that the water contact angles(WCA) rise with the increase of surface roughness, especially, the water contact angle on the PC surfaces prepared with specifications of 635mesh screen can reach to 152.3°, alias super hydrophobic surfaces.

scholarly journals Sialon and Alumina Modified UV-Curable Coatings with Improved Mechanical Properties and Hydrophobicity

Coatings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1424
Author(s):  
Mariola Robakowska ◽  
Łukasz Gierz ◽  
Hubert Gojzewski
Keyword(s):  
Mechanical Properties ◽  
Contact Angle ◽  
Inorganic Compounds ◽  
Surface Hydrophobicity ◽  
Scratch Resistance ◽  
Aluminum Oxynitride ◽  
Uv Curable ◽  
Scratch Hardness ◽  
Coating Surface ◽  
Inorganic Fillers

This article describes the modification of UV-curable coatings with silicon aluminum oxynitride (Sialon) and aluminum oxide (Alu C), which improve the hydrophobicity of the coating surface and the scratch hardness. The contact angle is greater due to surface roughness being enhanced with inorganic fillers. Improved scratch resistance results from the formation of a sliding layer triggered by the diffusion of Sialon or alumina on the coating surface. One can observed an increase in the surface hydrophobicity as well as in the scratch hardness (up to 100%) when small amounts (5 wt.%) of the inorganic compounds are added. Imaging microscopies, i.e., SEM, OM, and AFM (with nanoscopic Young’s modulus determination), revealed the good distribution of both types of fillers in the studied matrix.

scholarly journals Feedback of outflows in the Taurus Molecular Cloud

2012 ◽  
Vol 8 (S292) ◽  
pp. 47-47
Author(s):  
Huixian Li ◽  
Di Li ◽  
Rendong Nan
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Molecular Cloud ◽  
Feedback Effect ◽  
Total Kinetic Energy ◽  
Gravitational Potential Energy ◽  
Taurus Molecular Cloud

AbstractWe collected 27 outflows from the literature and found 8 new ones in the FCRAO CO maps of the Taurus molecular cloud. The total kinetic energy of the 35 outflows is found to be about 3% of the gravitational potential energy from the whole cloud. The feedback effect due to the outflows is minor in Taurus.

scholarly journals Surface Tracking of MgO/Epoxy Nanocomposites: Effect of Surface Hydrophobicity

2019 ◽  
Vol 9 (3) ◽  
pp. 413 ◽  
Author(s):  
Zhaoliang Xing ◽  
Chong Zhang ◽  
Xiangnan Hu ◽  
Panhui Guo ◽  
Jingyuan Zhang ◽  
...  
Keyword(s):  
Contact Angle ◽  
Electric Fields ◽  
Surface Hydrophobicity ◽  
Surface Charges ◽  
Surface Tracking ◽  
Surface Contact ◽  
Surface Contact Angle ◽  
Tracking Behavior ◽  
Composite Samples ◽  
Reduced Surface

Surface tracking has been one of the challenges for outdoor organic insulations, in electronic and electrical devices. In this paper, surface tracking behavior of nano-MgO/epoxy composite samples were measured according to the standard IEC 60112. Improved tracking resistance was obtained in nanocomposites with an 18.75% uplift in the comparative tracking index, and a decrease of 58.20% in the surface ablation area at a fixed 425 V. It was observed that the tracking resistance and surface hydrophobicity shared the same tendency—both, the comparative tracking index and surface contact angle increased with an increase of the nanofiller content. Samples with better hydrophobicity exhibited a higher tracking resistance. It could be the case that the conductive pathway of contamination was harder to form, as a result there were fewer discharging processes. With the development of surface tracking, the surface contact angle abruptly decreased, at first, and tended to be constant, which was also accomplished with the failure of samples. In addition, reduced surface resistivity was also found in the nanocomposites, which was beneficial for releasing surface charges and inhibiting distortions in the electric fields.

scholarly journals Rapidly rotating strange stars

2000 ◽  
Vol 177 ◽  
pp. 661-662 ◽  
Author(s):  
D. Gondek-Rosińska ◽  
P. Haensel ◽  
J. L. Zdunik ◽  
E. Gourgoulhon
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Quark Mass ◽  
Strange Quark ◽  
Gravitational Potential Energy ◽  
Rapid Rotation ◽  
Strange Stars ◽  
Absolute Value ◽  
Strange Quark Mass ◽  
Global Parameters

AbstractWe study effects of the strange quark mass,ms, and of the QCD interactions, calculated to lowest order inαc, on the rapid rotation of strange stars (SS). The influence of rotation on global parameters of SS is greater than in the case of the neutron stars (NS). We show that independently ofmsandαcthe ratio of the rotational kinetic energy to the absolute value of the gravitational potential energyT/Wfor a rotating SS is significantly higher than for an ordinary NS. This might indicate that rapidly rotating SS could be important sources of gravitational waves.

scholarly journals Wettability on Different Surfaces

2020 ◽  
Author(s):  
Yeeli Kelvii Kwok
Keyword(s):  
Contact Angle ◽  
Textured Surface ◽  
Original Material ◽  
Textured Surfaces ◽  
Hydrophobic Surfaces ◽  
Hydrophilic Surfaces ◽  
Young's Equation

Wettability has been explored for 100 years since it is described by Young’s equation in 1805. It is all known that hydrophilicity means contact angle (θ), θ < 90°; hydrophobicity means contact angle (θ), θ > 90°. The utilization of both hydrophilic surfaces and hydrophobic surfaces has also been achieved in both academic and practical perspectives. In order to understand the wettability of a droplet distributed on the textured surfaces, the relevant models are reviewed along with understanding the formation of contact angle and how it is affected by the roughness of the textured surface aiming to obtain the required surface without considering whether the original material is hydrophilic or hydrophobic.

Dynamic contact angle effects onto the maximum drop impact spreading on solid surfaces

2009 ◽  
Vol 21 (12) ◽  
pp. 122002 ◽  
Author(s):  
D. C. Vadillo ◽  
A. Soucemarianadin ◽  
C. Delattre ◽  
D. C. D. Roux
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Drop Impact ◽  
Solid Surfaces
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