Capillarity Coefficient Research Articles

On the well-posedness for the Euler-Korteweg model in several space dimensions

The Euler-Korreweg model results from a modification of the standard Euler equations governing the motion of compressible inviscid fluids through the adjunction of the Korteweg stress tensor, which takes into account capillarity effects in regions where the density experiences large variations, typically across interfaces for fluids exhibiting phase changes. One of the main difficulties in the analysis of the Cauchy problem for this model, a third order system of conservation laws, is the absence of dissipative regularization, since viscosity is neglected. The Cauchy problem for isothermal fluids in one space dimension has been addressed by the authors in an earlier paper, using Lagrangian coordinates. Here the Cauchy problem is investigated in arbitrary space dimension N, still for isothermal fluids, and a variable capillarity coefficient. A local well-posedness result is obtained in Sobolev spaces as though the density gradient and the velocity field were solutions of a symmetrizable hyperbolic system. More precisely, well-posedness is shown for Hs+1 x H-s (s > N/2 + 1) perturbations of smooth global solutions, either constant states or traveling profiles. In addition, almost-global existence is proved for small enough perturbations, and a blow-up criterion is shown. Proofs rely on a suitable extended formulation of the system, which turns out to amount to a nonlinear degenerate Schrodinger equation coupled with a transport equation, and on a priori estimates without loss of derivatives for the extended system, which necessitate various 'gauge' functions to cancel out bad commutators.

Effect of curing conditions on the mortars with and without GGBFS

The effect of curing conditions on properties of mortars with and without ground granulated blast furnace slag (GGBFS) was studied. In the present work, cement was replaced by ground granulated blast furnace slag 0% (control), 30%, and 60% by weight, and mortars were produced. One of the two groups of mortars was kept in water at 20 °C standard conditions, and the other was kept in moisture cabinet at 40 °C temperature and approximately at 100% relative humidity (RH). Flexural strength, compressive strength, ultrasonic pulse velocity, capillarity coefficient, and volumetric water absorption were investigated at the ages of 7, 28, 56, 90, and 180 days. The results obtained indicate that elevated temperature increases performance of mortar at early ages but decreases at later-age, and this affect is more significant at slag replaced mortars.

Effects of expanded perlite aggregate and different curing conditions on the physical and mechanical properties of self-compacting concrete

Fresh self-compacting concrete (SCC) flows to place and around obstructions under its own weight to fill the formwork completely and is self-compact, without any segregation. This article outlines compressive strength, apparent porosity and capillarity coefficient of SCC including mixture of expanded perlite aggregate (EPA) and natural aggregates (NA) at different curing conditions. The binder (cement + silica fume) dosage was held constant at 450 kg / m 3 throughout this study. Superplasticizer 2% by weight of Portland cement (PC) was used to reduce water/binder (w/cm) ratios. It was found that the capillarity coefficient and apparent porosity of concrete is increased by using EPA and that the compressive strength of EPA concrete generally decreases with increasing EPA ratios. Another experimental finding was that, at the cured in air (CC2) curing conditions, SCC shows both the highest capillarity coefficient and the apparent porosity and lowest compressive strength after 28 days.

Influence of different curing conditions on the physical and mechanical properties of concretes with admixtures of silica fume and blast furnace slag

Adequate curing is essential for the proper strength development, imperviousness and durability of concrete and concrete structures. In practice, structural concrete is seldom moist-cured for more than 7 days. Experimental studies are applied in determining the influence of a mineral admixture on the microstructure, capillary and porosity of concrete. The strength development and durability of concretes with silica fume (SF) and blast furnace slag (BFS) are reported to be critically dependent on the extent of curing and curing conditions. To improve the physical and mechanical properties of concrete, SF and BFS were used at different ratio instead of normal portland cement (PC). The dry unit weight, the compressive strength, the ultrasonic pulse velocity (UPV), capillarity coefficient and appearing porosity (AP) of the specimens were determined. The specimens were cured in different curing regimes for periods varying from 28, 75, 150, to 400 days before exposure to the experiments. Finally, it was observed that the specimens with SF%10+BFS%20 and 0.35 water–binder ratios had the highest compressive strength and UPV, the lowest capillarity coefficient and the appearing porosity. As a result, it can be concluded that the mineral admixtures improved the compressive strength, UPV, capillarity coefficient and appearing porosity.

Relationship between liquid sorptivity and capillarity in concrete

Neutron radiography (NR) was applied to study liquid transport processes in concrete. With this method, it is possible to monitor the liquid distribution inside specimens and to measure the height of the liquid front for liquids of high hydrogen content inside concrete. The experiment was performed with water and fuel oil for three different types of concrete. The results are compared with the sorptivity measured by the gravimetric method. It is shown that the ratio between the capillarity coefficient and sorptivity depends upon the combination of liquid and solid phases. For water, this value was found to be 5.5±0.6, 5.8±0.6 and 7.1±0.7 in concrete without additives, concrete with an air-entraining agent and concrete with a plasticizer, respectively. For fuel oil, the value is about 50% higher than that for water.

Influence of mineral admixtures on the some properties and corrosion of steel embedded in sodium sulfate solution of concrete

The corrosion of steel reinforcement is the most significant factor of deterioration in reinforced concrete structures. Corrosion of embedded steel in concrete may occur as a result of the depassivating effects of sulfate ions. Corrosive ions around the steel, at the passive state, destroy the reinforced concrete. To improve the mechanical and physical properties of concrete and to increase the corrosion resistance of steel embedded in concrete, silica fume (SF) and blast furnace slag (BFS) were used at different ratios instead of portland cement (PC). The workability, dry unit weight, the compressive strength and capillarity coefficient of the samples without steel reinforcement were determined. The corrosion current densities were measured by the linear polarization technique on the 28th, 75th, 150th and 250th days. Finally, it was observed that the samples with 10% SF+20% BFS had the highest compressive strength and the lowest capillarity coefficient. The concrete samples with 10% SF+40% BFS and 0.35 water–binder ratios (W/C) had the lowest corrosion current density. As a result, it can be concluded that the mineral admixtures improved the compressive strength, capillarity coefficient and corrosion current density.

On Some Compressible Fluid Models: Korteweg, Lubrication, and Shallow Water Systems

In this article, we give some mathematical results for an isothermal model of capillary compressible fluids derived by Dunn and Serrin in [1]Dunn JE, Serrin J. On the thermodynamics of interstitial working. Arch Rational Mech Anal. 1985; 88(2):95–133), which can be used as a phase transition model. We consider a periodic domain Ω = T d (d = 2 ou 3) or a strip domain Ω = (0,1) × T d −1. We look at the dependence of the viscosity μ and the capillarity coefficient κwith respect to the density ρ. Depending on the cases we consider, different results are obtained. We prove for instance for a viscosity μ(ρ) = νρ and a surface tension the global existence of weak solutions of the Korteweg system without smallness assumption on the data. This model includes a shallow water model and a lubrication model. We discuss the validity of the result for the shallow water equations since the density is less regular than in the Korteweg case.

Stick-Slip Interface Motion as a Singular Limit of the Viscosity-Capillarity Model

This work is a follow-up on a study by Vainchtein and Rosakis of interface dynamics and hysteresis in materials undergoing solid-solid phase transitions. The author investigates the dynamics of a bar with a nonconvex double-well elastic energy density. The model includes both viscosity and strain-gradient capillarity terms. Viscous stress provides eiergy dissipation. The capillarity term models interfacial energy. The bar is subject to time-dependent displacement boundary conditions. Numerical simulations predict hysteretic behavior in the overall load-elongation diagram. The hysteresis is primarily due to metastability and persists even at very slow loading when viscous dissipation is small. At a given loading, a large capillarity coefficient a results in a smooth interface motion and small hysteresis loop. As a becomes smaller, the loop grows and acquires serrations, while the interface motion alternates between slow and fast regimes. The results suggest that the stick-slip interface motion and serrated hysteresis loop predicted by Vainchtein and Rosakis in the absence of interfacial energy are a singular limit of the viscosity-capillarity model as the capillarity coefficient tends to zero. The irregular interface motion and serrated load-elongation curves qualitatively agree with some experimental observations in shape-memory alloys.

PENETRATION COEFFICIENT IN POROUS MEDIA

In the case of horizontal infiltration in an air-dry soil with a zero hydrostatic head, the penetration coefficient is defined as the distance of advance of the visible wetting front per square root of unit time. Such infiltration experiments have been conducted in 53− to 63-micrometer, 74− to 88-micrometer, and 105− to 125-micrometer glass bead fractions, successively, with 100 percent water, 6 and 20 percent ethyl alcohol water solutions, 100 percent ethyl and 100 percent methyl alcohol. Penetration coefficient in porous media is found to be composed of vapor penetration coefficient and a capillarity coefficient. Liquid infiltration in porous media results from two mechanisms dealing simultaneously with the fluid particles in the vapor and the liquid phases. In the vapour phase, the fluid particles are adsorbed and condensed on the solid matrix to form a liquid film, and, in the liquid phase, the fluid particles are moved mostly by capillary forces. Poiseuille's law is found to govern the penetration of water, but not other liquids, in porous media. The shape factor G is found to be much higher than 8 for uniform capillary tubes. This study supplies the basis for applying capillary tube models in the hydrodynamics of porous media.

Deformation of the glass in the zone of formation of a hollow glass fiber

An equation has been derived for the deformation of the glass in the zone of formation of a hollow glass fiber, and the nature of the deformation along the length of the "bulb" has been determined. The principal technological factors controlling the capillarity coefficient of the fiber have been established and their interactions are shown to affect the geometric characteristics of the fiber. The region of existence of the hollow fiber formation process has been determined. There is satisfactory agreement between the experimental and theoretical data.

Effectiveness of using hollow fibers to improve the rigidity of glass-reinforced plastics

Calculated and experimental relations between the modulus of elasticity and rigidity of unidirectional glass-reinforced plastics (GRP) and the capillarity coefficient of the hollow fiber reinforcement are presented. It is established that in calculating the flexural rigidity ratio of hollow- and solid-fiber GRP specimens of equal weight it is not permissible to neglect the mass and modulus of elasticity of the resin. The potentialities of hollow fibers as reinforcement for GRP shells subjected to external pressure are demonstrated.