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The lateral motion of a droplet after its impact on groove-patterned superhydrophobic surfaces is numerically studied in the present work. Different from previous studies, the wettability gradient is not required to produce lateral motions. Instead, a substrate with two halves decorated with same Cassie area fractions but different length ratios is used and four different motions can be observed by varying the impact velocity. The asymmetrical penetration into the grooves of the substrate is found to be the main reason for triggering the different motions. The penetrated liquid could bring upward momentum to lift the droplet from one side of the substrate, or it could block the retracting contact line from one side. As a result, different oblique motion components are generated and added to the vertical rebound motion, finally leading to the different lateral motions. Our simulation findings provide a fresh idea for the control of droplet motion by coating the solid surfaces.

The hysteresis in two phase relative permeability occurs when the saturation history of the flow changes from drainage to imbibition or vice versa. The imbibition relative permeability is a strong function of initial non-wetting phase saturation from which the imbibition process starts. Hence, it is very time-consuming to conduct many experiments for measuring all possible imbibition relative permeability (kr) data. An alternative approach is to predict the imbibition relative permeability using the measured Land trapping coefficient and primary drainage relative permeability. Some predictive models, found in the literature, such as that of Land, Carlson and Killough are available in commercial simulators. For prediction of imbibition data, these models require the primary drainage kr data and one set of imbibition kr data to calculate the corrected Land trapping coefficient. However, the imbibition relative permeability is not always available and the inappropriate use of these models can introduce significant errors in the calculations. In this study, the limitations of the available models are discussed and a modified method is suggested, which only requires the primary drainage kr data and the measured Land trapping coefficient. The available models for prediction of imbibition kr data are based on the calculations of trapped non-wetting saturation ( S n w t ). Therefore, in this study, a modified method was introduced which improved the estimations of trapped non-wetting phase saturation. The predicted values of imbibition relative permeability using this improved method were in good agreement with the experimental data. It was shown that this method can be used for both gas and oil as non-wetting phases in a water-wet medium. However, the trapped non-wetting phase is a function of capillary number and the Land trapping coefficient changes as the capillary number changes. Hence, the measured Land trapping coefficient cannot be assumed as constant in cases where severe changes in pressure result in changing interfacial tension (IFT) and fluid viscosity.

In the present study, the spontaneous uptake of droplets into non-wetting capillaries was simulated by using many-body dissipative particle dynamics. The simulated results show that the droplets undergo a spontaneous uptake even for a non-wetting capillary. In contrast to the liquid in a reservoir in which the direction of liquid spontaneous movement in the capillary depends on the wettability, the moving direction of droplets in the capillary relies not only on the surface wettability but also the radius of the droplets. We give an explanation from the viewpoint of force balance. Our results demonstrate that capillary force could be used to drive liquid in microfluidics.

Non wettable surfaces have attracted attention for their promising potential in anti-fouling and self-cleaning applications. However, the complex fabrication and loss of super-hydrophobicity because of poor durability have restricted their commercial applications. To address these issues, a robust super-hydrophobic surface was fabricated through construction of a coral-reef like fibrous structure, followed by adhesive-assisted dip coating. Wrinkled fibrous nano silica (WFNS) was synthesized using the Winsor III system. WFNS having hierarchal surface and enhanced surface area was modified by salinizing agent and by coated on various substrates. This fibrous structure aids to minimize the water/solid interface resulted to achieve the super-hydrophobic surface with a water contact angle of 167°. To impart mechanical and chemical robustness, an adhesive-assisted approach was used. The as-prepared surface maintained a remarkable super-hydrophobicity even after mechanical and chemical stresses. The prepared super-hydrophobic surface illustrated excellent anti-fouling performance against corrosive liquids and an antimycotic property. The combination of liquid repellency and exceptional robustness exhibited indicates the WFNS as a promising candidate for super-hydrophobic and self-cleaning applications.

In this work, we investigate the impact of co-current to counter-current flow reversals on the migration dynamics of a non-wetting phase plume in a porous medium. The presented results and observations have direct application to CO2 injection into saline aquifers where a less dense CO2-rich plume migrates during and following the injection period. Counter-current gravity segregation experiments were performed in a vertical glass-bead pack with brine and iC8 as analog fluids to mimic the behavior of a CO2/brine system of relevance to CO2 sequestration processes. Four-electrode resistivity measurements were used to monitor the migration of the non-wetting phase (iC8) by relating the resistivity index (RI) to the brine saturation. The observations are compared with numerical calculations to demonstrate that standard co-current relative permeability measurements are inadequate to reproduce the experimental observations. A reduction in the relative permeability of both phases, in particular for the non-wetting phase, is required to improve the agreement between experimental observations and numerical calculations. Numerical calculations based on co-current input data predicts a much faster migration of the non-wetting phase to the top of the column than what is observed in the segregation experiments. Our findings demonstrate that counter-current flow affects the phase's mobilities, because of interfacial coupling, and should therefore be considered in the modeling of injection/storage of CO2 in saline aquifers: simulation of CO2/brine dynamics based on co-current relative permeability measurements is likely to render estimates of migration time/distance in significant error.

During the reflood of a Pressurised Water Reactor (PWR) following a loss of coolant accident, precursory cooling prior to the arrival of the rewetting front is of vital importance in limiting the rise in cladding temperature before rewet. This precursory cooling is achieved by a flow of superheated vapour, with entrained saturated drops, which evaporate into the vapour and act as a heat sink. In this paper we investigate a complementary mechanism; the direct cooling of the cladding by the drops themselves. Cladding temperatures are such that wetting by these droplets does not occur. On the contrary, droplets bounce off a vapour cushion formed during the ∼10 ms or so that they are in close proximity to the cladding. Using a combination of previous experimental correlations and recent CFD calculations, we estimate the rate of heat removal from the cladding surface as a result of the droplet impingement. Thus, we estimate the heat removed as a result of one impingement and estimate the total rate of heat removal by estimating the number droplets impinging on the cladding per unit surface area. The heat extracted by those droplets is found to be about 1/10 of the heat extracted by single-phase vapour under typical reflood conditions. Though there significant uncertainties in these estimates, it does seem that direct cooling by droplets, not generally incorporated in analyses of reflood, could actually be making a significant contribution to keeping cladding temperatures down to acceptable levels.

Research into formation of hollow granules from liquid marbles is an emerging field in hydrophobic granulation. A liquid marble is formed by a network of self-assembled hydrophobic powder around a droplet, and this paper investigates the conditions required for forming hollow granules from a liquid marble precursor. Single drops of fluid were produced using a syringe and placed onto loosely packed powder beds of hydrophobic powders. Liquid marbles formed from several powder/liquid combinations were dried at several conditions to investigate the drying conditions required for formation of a stable hollow granule. The formation of stable hollow granules was found to depend on drying temperature and binder concentration. For HPMC and PVP binder, formation of hollow granule is proportional to binder viscosity and for HPC binder, this relationship is constant. Different combinations of powder and binder at both drying temperatures – 60 °C and 100 °C – had mixed success rates in forming hollow granules, but generally the success rate was improved by using higher drying temperatures, smaller particles or higher viscosity binder fluids.

We measure the trapped non-wetting phase saturation as a function of the initial saturation in sand packs. The application of the work is for carbon dioxide (CO2) storage in aquifers where capillary trapping is a rapid and effective mechanism to render injected CO2 immobile. We used analogue fluids at ambient conditions. The trapped saturation initially rises linearly with initial saturation to a value of 0.11 for oil/water systems and 0.14 for gas/water systems. There then follows a region where the residual saturation is constant with further increases in initial saturation.

A phenomenological qualitative theory of elastic effects is used to examine wetting near critical points in the solid state.

The spreading of a spherical droplet, put in contact with a flat solid surface, is simulated using Monte-Carlo algorithm. Two wetting regimes are investigated by changing the energy E ls between atom of droplet (1) and atom of solid (s) and the energy E ll between two droplet atoms: the partial wetting regime and the non-wetting regime. When dealing with the partial wetting regime, a droplet with liquid cap and layered foot is obtained. After the collapse of the liquid cap, a layered droplet with terraces appears at low temperature. At higher temperature, the layers vanish and the liquid cap appears again. When dealing with the non-wetting regime, the droplet ∣ solid interface is reduced to a minimum, as if the droplet was expelled from the solid surface. Whereas molecular dynamics can only handle atomic time scales in the range (ca. 10 −12 to 10 −7 s), it is proved here that the Monte-Carlo algorithm can probe macroscopic time scales (ca. 10 −3 s), whose results are reported here, for the first time, to our knowledge.

A model based on invasion percolation was used to simulate the migration on a non-wetting fluid through a porous medium filled with an immiscible wetting fluid under the influence of a gradient such as that provided by gravity. The migrating fluid clusters undergo both fragmentation and coalescence. The fragment size distribution obtained from two-dimensional simulations in which the gradient g is slowly increased from 0 can be represented by the scaling form Ns(g)∼s-2ƒ(s⧸|g|-z where z=1+(D−1)ν⧸(ν+1). Here D is the fractal dimensionality of invasion percolation, with trapping, and ν is the ordinary percolation correlation length exponent.

Current concepts regarding lubrication are briefly reviewed and a new lubrication principle based on the use of non-wetting liquids is presented. Experimental tests are described, and the results show the validity of the principle. Technological difficulties which need to be overcome for industrial designs are outlined. This new principle is also considered to be part of the processes involved in animal or human joint lubrication.

Patients will be selected wearing PMMA ora hard gas permeable lens, who are having particular problems. The problems designated are: a poor or non wetting contact lens surface with or without accompanying punctuate epithelial erosions. These patients will be refitted with a lower wetting angle material; and the effects of wear on the contact lens surface, and on the cornea, willbe discussed.

In a previous paper the experimental equilibrium configurations of a nonwetting liquid in an ampoule were described. Theoretical analyses of these configurations are described here. In a cylindrical ampoule a bubble/bridge configuration is predicted to be stable only up to a critical volume of gas, beyond which separated columns of liquid form. This critical bubble volume decreases as the contact angle of the liquid on the ampoule increases. In a triangular ampoule the liquid contacts the ampoule along the center of the faces and not in the corners. As the contact angle increases beyond 90 deg, the contact width decreases.

To explain why nonwetting metals and semiconductors, directionally solidified in space, yield ingots which are smaller in diameter than the ampoule, the behavior of mercury during a parabolic free-fall in a KC135 aircraft was observed using transparent ampoules with attached video cameras. Triangular glass ampoules and cylindrical polycarbonate ampoules were filled to 30-95 percent capacity. In polycarbonate ampoules, mercury did not pull away from the ampoule walls. The photographs displayed either liquid columns separated by gas spaces or gas bubbles on the wall. At low levels of liquid, separated columns were favored, while only bubbles were seen when the liquid mercury almost filled the ampoule. In ampoules with triangular cross section, the liquid pulled away from the glass walls along the edges and contacted the walls along the centers, over about half of the wall width of each side.