scholarly journals Water entry of spheres with various contact angles

2019 ◽  
Vol 862 ◽  
Author(s):  
Nathan B. Speirs ◽  
Mohammad M. Mansoor ◽  
Jesse Belden ◽  
Tadd T. Truscott
Keyword(s):  
Contact Angle ◽  
Weber Number ◽  
Bond Number ◽  
Water Entry ◽  
Contact Angles ◽  
Cavity Formation ◽  
Liquid Impact ◽  
Critical Impact Velocity ◽  
Solid Liquid ◽  
Rough Sphere

It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid–liquid contact angle; Duez et al. (Nat. Phys., vol. 3 (3), 2007, pp. 180–183). Using a rough sphere with a contact angle of $120^{\circ }$ , Aristoff & Bush (J. Fluid Mech., vol. 619, 2009, pp. 45–78) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasistatic, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: (1) cavity shape also depends on the contact angle; (2) the absence of a splash crown at low Weber number results in cavity formation below the predicted critical velocity. In addition, we use alternate scales in defining the Bond, Weber and Froude numbers to predict the cavity shapes and scale pinch-off times for various impacting bodies (e.g., spheres, multidroplet streams and jets) on the same plots, merging the often separated studies of solid–liquid and liquid–liquid impact in the literature.

Temperature-Dependent Wettability of Water on a Nickel Surface at Pressurized Condition: A Molecular Dynamics Study

2019 ◽  
Author(s):  
Dong-Lei Zeng ◽  
Biao Feng ◽  
Jia-Wen Song ◽  
Li-Wu Fan
Keyword(s):  
Contact Angle ◽  
Hydrogen Bonds ◽  
Average Energy ◽  
Contact Angles ◽  
Nickel Surface ◽  
Free Energies ◽  
Water Droplets ◽  
Temperature Dependent ◽  
Interfacial Free Energies ◽  
Solid Liquid

Abstract Temperature-dependent wettability of water droplets on a metal surface in a pressurized environment is of great theoretical and practical significance. In this paper, molecular dynamic simulation is used to study this problem by relating the temperature-dependent apparent contact angles to the changes in solid-liquid and solid-vapor interfacial free energies and hydrogen bonds in the nano-sized water droplets with increasing the temperature. The temperature range of interest is set from 298 K to 538 K in a 20 K interval under a constant pressure of 7 MPa. The results show that the contact angle in general decreases with raising the temperature and decreasing trend can be divided into two sections with different slopes. The contact angle drops slowly when the temperature is below 458 K as a critical point. Beyond this point, the contact angle shows a much steeper decrease. The difference between solid-vapor and solid-liquid interfacial free energies is found to decrease slightly with temperature. Combining with that the surface tension drops with increasing the temperature, a decreasing trend of the contact angle is expected according to the Young’s equation. As the temperature increases, the number and average energy of the hydrogen bonds both decrease, and the hydrogen bonds tend to aggregate at the bottom of the nano-droplets.

scholarly journals Amphiphobic Nanostructured Coatings for Industrial Applications

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 787 ◽  
Author(s):  
Federico Veronesi ◽  
Giulio Boveri ◽  
Mariarosa Raimondo
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Photoelectron Spectroscopy ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Friction Reduction ◽  
Hybrid Coatings ◽  
Wetting Behavior ◽  
Wide Range ◽  
Solid Liquid

The search for surfaces with non-wetting behavior towards water and low-surface tension liquids affects a wide range of industries. Surface wetting is regulated by morphological and chemical features interacting with liquid phases under different ambient conditions. Most of the approaches to the fabrication of liquid-repellent surfaces are inspired by living organisms and require the fabrication of hierarchically organized structures, coupled with low surface energy chemical composition. This paper deals with the design of amphiphobic metals (AM) and alloys by deposition of nano-oxides suspensions in alcoholic or aqueous media, coupled with perfluorinated compounds and optional infused lubricant liquids resulting in, respectively, solid–liquid–air and solid–liquid–liquid working interfaces. Nanostructured organic/inorganic hybrid coatings with contact angles against water above 170°, contact angle with n-hexadecane (surface tension γ = 27 mN/m at 20 °C) in the 140–150° range and contact angle hysteresis lower than 5° have been produced. A full characterization of surface chemistry has been undertaken by X-ray photoelectron spectroscopy (XPS) analyses, while field-emission scanning electron microscope (FE-SEM) observations allowed the estimation of coatings thicknesses (300–400 nm) and their morphological features. The durability of fabricated amphiphobic surfaces was also assessed with a wide range of tests that showed their remarkable resistance to chemically aggressive environments, mechanical stresses and ultraviolet (UV) radiation. Moreover, this work analyzes the behavior of amphiphobic surfaces in terms of anti-soiling, snow-repellent and friction-reduction properties—all originated from their non-wetting behavior. The achieved results make AM materials viable solutions to be applied in different sectors answering several and pressing technical needs.

scholarly journals On the limitations of the applicability of Young’s equations temperature

2021 ◽  
Vol 23 (2) ◽  
pp. 218-222
Author(s):  
Magomed Pashevich Dokhov
Keyword(s):  
Contact Angle ◽  
Surface Energy ◽  
Interfacial Energy ◽  
Contact Angles ◽  
Surface Phenomena ◽  
Surface Energies ◽  
Three Phase ◽  
Production Techniques ◽  
The Difference ◽  
Solid Liquid

The article uses the thermodynamics of interfacial phenomena to justify the fact that Young’s equations can correctly describe the three-phase equilibrium with any type of interatomic bonds. Wetting, adhesion, dissolution, surface adsorption, and other surface phenomena are important characteristics, whichlargely determine the quality and durability of materials, and the development of a number of production techniques, including welding, soldering, baking of metallic and non-metallic powders, etc. Therefore, it is important to study them.Using experimental data regarding surface energies of liquids (melts) and contact angles available in the literature, we calculated the surface energies of many solid metals, oxides, carbides, and other inorganic and organic materials without taking into account the amount of the interfacial energy at the solid-liquid (melt) interface. Some researchers assumed that in case of an acute contact angle the interfacial energy is low. Therefore, they neglected it and assumed it to be zero.Others knew that this value could not be measured, that is why they measured and calculated the difference between the surface energy of a solid and the interfacial energy of a solid and a liquid (melt), which is equal to the product of the surface energy of this liquid by the cosine of the contact angle. It is obvious that these methods of determining the surface energy based on such oversimplified assumptions result in poor accuracy.Through the use of examples this paper shows how the surface energies of solids were previously calculated and how the shortcomings of previous calculations can be corrected

scholarly journals Effect of Direct Current on Solid-Liquid Interfacial Tension and Wetting Behavior of Ga–In–Sn Alloy Melt on Cu Substrate

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Limin Zhang ◽  
Ning Li ◽  
Hui Xing ◽  
Rong Zhang ◽  
Kaikai Song
Keyword(s):  
Contact Angle ◽  
Interfacial Tension ◽  
Direct Current ◽  
Sessile Drop ◽  
Contact Angles ◽  
Current Intensity ◽  
Solute Diffusion ◽  
Wetting Behavior ◽  
Cu Substrate ◽  
Solid Liquid

The effect of direct current (DC) on the wetting behavior of Cu substrate by liquid Ga–25In–13Sn alloy at room temperature is investigated using a sessile drop method. It is found that there is a critical value for current intensity, below which the decrease of contact angle with increasing current intensity is approximately linear and above which contact angle tends to a stable value from drop shape. Current polarity is a negligible factor in the observed trend. Additionally, the observed change in contact angles is translated into the corresponding change in solid-liquid interfacial tension using the equation of state for liquid interfacial tensions. The solid-liquid interfacial tension decreases under DC. DC-induced promotion of solute diffusion coefficient is likely to play an important role in determining the wettability and solid-liquid interfacial tension under DC.

The Effect of Solid Surface Roughness on Dynamic Contact Angles in Solid-Liquid-Liquid Systems

2002 ◽  
Author(s):  
Dandina N. Rao ◽  
Hussain H. Radwani
Keyword(s):  
Surface Roughness ◽  
Contact Angle ◽  
Solid Surface ◽  
Water System ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Solid Surfaces ◽  
Liquid Systems ◽  
L Systems ◽  
Solid Liquid

The engineering applications of spreading and adhesion phenomena involving fluids on solids are numerous. The adhesive and spreading interactions at the solid-fluid interfaces are well characterized by dynamic contact angles. This study reports on the results of an experimental investigation into the effect of solid surface roughness on dynamic contact angles in solid-liquid-liquid (S-L-L) systems. The experiment involved the use of Wilhelmy Plate apparatus to measure adhesion tension (which is the product of interfacial tension and cosine of the contact angle between the liquid-liquid interface and the solid surface), the DuNuoy tensiometer to measure the liquid-liquid interfacial tension, and a profilometer to characterize the roughness of the solid surfaces used. The components of the solid-liquid-liquid systems studied consisted of: (i) smooth glass, roughened quartz and an actual rock surface for the solid phase, (ii) normal-hexane and deionized water as the two immiscible liquid phases. The dynamic contact angles (advancing and receding angles) of the three-phase (rock-oil-water) system provide essential information about the wettability of petroleum resrvoirs. The wettability of a reservoir is an important parameter that affects oil recovery in primary, secondary, and enhanced recovery operations [1]. Contact angle measurements on smooth surfaces are generally used to characterize reservoir wettability. However pore surfaces within reservoir rocks are essentially rough and hence it is important to determine the effect of such roughness on measured contact angles. There is very little information in the open literature on the effect of surface roughness on dynamic contact angles in S-L-L systems. In the present work, four levels of roughness of solid surfaces of similar mineralogy (quartz and glass) were tested in hexane-deionized water fluid pair. The advancing and receding contact angles measured at ambient conditions were analyzed for wettability effects. It was found that as surface roughness increased, the dynamic contact angles also increased. The wettability of the rock-oil-water system shifted from weakly water-wet for the smooth glass to intermediate-wet for the roughened surface. The general trends observed in our study were found to be in good agreement with other published results. However, the generally held notion of increasing contact angle hysteresis with increasing roughness appears to be incorrect in solid-liquid-liquid systems.

Wetting

Surfactants ◽  
2019 ◽  
pp. 427-464
Author(s):  
Bob Aveyard
Keyword(s):  
Contact Angle ◽  
Solid Surface ◽  
Contact Angles ◽  
Surface Forces ◽  
Solid Surfaces ◽  
Surface Topology ◽  
Spreading Coefficient ◽  
Surfactant Solutions ◽  
Receding Contact ◽  
Solid Liquid

Wetting of one liquid by another can be understood in terms of the spreading coefficient; the relevance of surface forces to wetting is also explained. If a small liquid drop does not spread, it forms a lens whose shape is determined by the various interfacial tensions. The wetting of solids is characterized by the contact angle θ‎ of the liquid with the solid surface; θ‎ usually depends on how a configuration is reached and advancing and receding contact angles are defined. It is often useful notionally to split solid/liquid tensions into polar and nonpolar contributions in the treatment of wetting. Effects of surfactant on the wetting of both hydrophobic and hydrophilic solids by water are explored. Surface topology can greatly influence wettability, and superhydrophobic solid surfaces exist widely in nature. Finally some dynamic aspects of wetting of solid surfaces by surfactant solutions are described briefly.

Mass-Area Method to Measure the Contact Angle on Hydrophilic Surfaces

2011 ◽  
Author(s):  
Hie Chan Kang ◽  
Anthony M. Jacobi
Keyword(s):  
Contact Angle ◽  
Present Method ◽  
Contact Angles ◽  
Solid Materials ◽  
Spherical Cap ◽  
Present Measurement ◽  
Area Method ◽  
Hydrophilic Surfaces ◽  
Solid Liquid Interface ◽  
Solid Liquid

A mass-area method is proposed to overcome problems in the measurement of the equilibrium contact angles for rough and hydrophilic surfaces. A goniometer usually measures the contact angle at the top plane of a rough surface, not the contact line of the solid-liquid interface. The present method estimates the contact angle indirectly from the volume of the liquid and the size of the contact area, assuming a spherical cap and consistent with a minimization of the free energy. The present method shows a roughly linear relationship with measurements by a goniometer for smooth surfaces of various solid materials with various liquids, but the goniometer measurements are smaller. An example test and the error of the present measurement method are presented and discussed.

scholarly journals Superhydrophobicity and Contact-Line Issues

MRS Bulletin ◽  
2008 ◽  
Vol 33 (8) ◽  
pp. 747-751 ◽  
Author(s):  
Lichao Gao ◽  
Alexander Y. Fadeev ◽  
Thomas J. McCarthy
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Contact Angle Hysteresis ◽  
Water Repellency ◽  
Contact Angles ◽  
Single Step ◽  
Contact Lines ◽  
Lotus Effect ◽  
Three Phase ◽  
Solid Liquid

AbstractThe wettability of several superhydrophobic surfaces that were prepared recently by simple, mostly single-step methods is described and compared with the wettability of surfaces that are less hydrophobic. We explain why two length scales of topography can be important for controlling the hydrophobicity of some surfaces (the lotus effect). Contact-angle hysteresis (difference between the advancing, θA, and receding, θR, contact angles) is discussed and explained, particularly with regard to its contribution to water repellency. Perfect hydrophobicity (θA/θR = 180°/180°) and a method for distinguishing perfectly hydrophobic surfaces from those that are almost perfectly hydrophobic are described and discussed. The Wenzel and Cassie theories, both of which involve analysis of interfacial (solid/liquid) areas and not contact lines, are criticized. Each of these related topics is addressed from the perspective of the three-phase (solid/liquid/vapor) contact line and its dynamics. The energy barriers for movement of the three-phase contact line from one metastable state to another control contact-angle hysteresis and, thus, water repellency.

Role of titanium on the reactive spreading of lead-free solders on alumina

2006 ◽  
Vol 21 (12) ◽  
pp. 3222-3233 ◽  
Author(s):  
Laurent Gremillard ◽  
Eduardo Saiz ◽  
Velimir R. Radmilovic ◽  
Antoni P. Tomsia
Keyword(s):  
Contact Angle ◽  
Sessile Drop ◽  
Triple Line ◽  
Contact Angles ◽  
Liquid Interface ◽  
Liquid Front ◽  
Wide Variability ◽  
Solid Liquid Interface ◽  
Lead Free Solders ◽  
Solid Liquid

The wetting of Sn3Ag-based alloys on Al2O3 has been studied using the sessile-drop configuration. Small additions of Ti decrease the contact angle of Sn3Ag alloys on alumina from 115° to 23°. Adsorption of Ti-species at the solid–liquid interface prior to reaction is the driving force for the observed decrease in contact angle, and the spreading kinetics is controlled by the kinetics of Ti dissolution into the molten alloy. The addition of Ti increases the transport rates at the solid–liquid interface, resulting in the formation of triple-line ridges that pin the liquid front and promote a wide variability in the final contact angles.

Spreading of Liquid Droplets on Cylindrical Surfaces: Accurate Determination of Contact Angle.

1989 ◽  
Vol 170 ◽  
Author(s):  
H. Daniel Wagner ◽  
E. Wiesel ◽  
H. E. Gallis
Keyword(s):  
Contact Angle ◽  
Liquid Droplet ◽  
Glass Fibers ◽  
Accurate Determination ◽  
High Strength ◽  
Contact Angles ◽  
Liquid Droplets ◽  
Liquid Polymers ◽  
Solid Liquid Interface ◽  
Solid Liquid

AbstractThe wetting of cylindrical monofilaments by liquid polymers is a problem of much scientific and technological importance. In particular, the characterization of the physicochemical nature of interfaces is a key problem in the field of advanced fibrous composites. The macroscopic regime contact angle, which reflects the energetics of wetting at the solid-liquid interface, is difficult to measure by usual methods in the case of very thin cylindrical fibers.In the present article a numerical method is proposed for the calculation of macroscopic regime contact angles from the shape of a liquid droplet spread onto a cylindrical monofilament. This method, which builds on earlier theoretical treatments by Yamaki and Katayama [1], and Carroll [2], very much improve the accuracy of the contact angle obtained. Experimental results with high-strength carbon, para-aramid, and glass fibers, are presented to demonstrate the high degree of accuracy of the method proposed.

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