Layer Compressibility Research Articles

Nonconventional hydrodynamics of smectic-A phases of liquid crystals: An experimental study of various compounds with the use of ultrasound.

This study concerns ultrasonic velocity and damping in the smectic-A phases of four liquid crystals, using a resonance technique. The compounds studied are terephthal-bis-p-p'-butylaniline (TBBA), octylcyanobiphenyl (8CB), octyloxycyanobiphenyl (8OCB), and p-cyanobenzylidene-p-octyloxyaniline (CBOOA). The results obtained for TBBA reveal abnormal damping behavior which shows that conventional hydrodynamics does not apply in the smectic-A phases of liquid crystals. Analysis of these results shows that anharmonic effects related to fluctuations in the smectic layers have an order of magnitude which is compatible with the lowest-order predictions of the theory of Mazenko, Ramaswamy, and Toner (MRT), when \ensuremath{\delta}${\ensuremath{\eta}}_{5}$0. Measurements taken on 8CB 8OCB, and CBOOA show that anharmonic effects are negligible in these three compounds at ultrasonic frequencies. This result is consistent with the lowest-order predictions of MRT theory. The difference between the behavior of TBBA and that of the other three compounds shows that anharmonic effects only appear at ultrasonic frequencies in compounds with a sufficiently high B/${K}_{1}$ value (B and ${K}_{1}$ are the layer compressibility and splay constants, respectively).

Discussion: Double layer theory and compressibility of clays

Discussion: Double layer theory and compressibility of clays

Effect of Initial Conditions on Constant Pressure Mixing Between Two Turbulent Streams

SummaryA study of the process of mixing and wake development has varied applications in wide ranging fields like jet ejectors, wake signatures, base pressure control, combustors, flow over cut-outs, jet noise and jet interactions. In real flows the wake is usually divided into two zones namely, the near field and the far field. The near field is usually controlled by initial conditions which involve two back-to-back boundary layers separating from the trailing edge of a solid surface. In the far field the flow becomes fully developed and assumes self similarity. The properties of fully developed far field have been well established but little is known about the near field. This paper describes the application of an integral analysis to study the effects of initial conditions like velocity ratio, initial boundary layer thickness, compressibility and temperature ratio on the development of near field of the turbulent mixing layer between two compressible, non-isoenergetic streams at constant pressure. Results include velocity and temperature profiles and the location of jet boundary line in the mixing layer. These results show the gradual approach of the mixing layer to self-preservation.

Double layer theory and compressibility of clays : Sridharan, A; Jayadeva, M S Geotechnique, V32, N2, June 1982, P133–144

Double layer theory and compressibility of clays : Sridharan, A; Jayadeva, M S Geotechnique, V32, N2, June 1982, P133–144

Double layer theory and compressibility of clays

The compressibility of pure clays under external load depends not only on the negative charges and crystallite morphology of clay minerals but also on the ion concentration, cation valency, dielectric constant and temperature of the pore fluid. The electrical double layer theory has been used by several investigators to derive the void ratio-pressure relationship of clays. This Paper presents a detailed study with regard to the Gouy—Chapman theory and the compressibility of clays. The relationship between the distance between parallel clay platelets and external pressure is shown to be almost independent of clay type. The surface area represents the clay type in showing the variations in void ratio-pressure (e–p) relationships of different clays. When the concentration of cations in the pore fluid is low, the log e–log p relationship is linear, and the compression index is a direct function of void ratio and independent of clay type. Examination of experimental results of other workers shows the validity of the Gouy—Chapman theory for predicting the e–p relationship qualitatively and, under certain circumstances, quantitatively. La compressibilité des argiles pures sous charge extérieure dépend non seulement des propriétés mécaniques des minéraux d'argile mais aussi des caractéristiques physicochimiques du fluide interstitiel. La théorie électrique des couches doubles a été employée par plusieurs rechercheurs pour représenter le rapport indice des vides/pression des argiles. Cet article offre une étude détaillée de la théorie Gouy-Chapman appliquée à la compressibilité des argiles. Le rapport entre la distance séparant les feuillets parallèles de l'argile et la pression extérieure est presque indépendant du type de sol. La zone superficielle représente le type d'argile, car elle indique les variations du rapport indice des vides/pressions des différentes argiles. Lorsque la concentration des cations dans le fluide interstitiel est basse le rapport log e/log p est linéaire et l'indice de compression est une fonction directe de l'indice des vides. Le dépouillement des résultats expérimentaux démontre que la théorie Gouy-Chapman est valable pour prédire le rapport e/p qualitativement et aussi quantitativement dans certaines circonstances.

The influence of molecular architecture on the surface activity of vinyl alcohol-acetate copolymers

The interfacial behavior of a family of blocky and random vinyl alcohol-acetate copolymers and their parent polyvinyl alcohol was studied. The vinyl acetate content and the intramolecular distribution were the only variables in the molecular architecture. Polymer adsorption and the effect of spread layers of these (co)polymers at the water- 1-butanol interface were studied with the static drop shape and the dynamic drop volume methods, and in addition with a novel method that records the retardation of mass transfer across an interface as caused by polymer adsorption. The three measuring techniques provide consistent views as to which molecular parameters determine the efficiency and mode of copolymer adsorption. Not the copolymer-solvent interaction parameter is relevant in this system, but rather the molecular architecture of the copolymers as expressed by the product of the mass average vinyl acetate sequence length and the vinyl acetate mole fraction. In addition, mass transfer studies provide information on the compressibility of the copolymer layers, the effectiveness of adsorption, and the onset of adsorption fractionation.

Observation of algebraic decay of positional order in a smectic liquid crystal

A smectic-$A$ liquid crystal in three dimensions has been predicted to exhibit algebraic decay of the layer correlations rather than true long-range order. As a consequence, the smectic Bragg peaks are expected to be power-law singularities of the form ${q}_{\ensuremath{\parallel}}^{\ensuremath{-}2+\ensuremath{\eta}}$ and ${q}_{\ensuremath{\perp}}^{\ensuremath{-}4+2\ensuremath{\eta}}$, where $\ensuremath{\parallel}(\ensuremath{\perp})$ is along (perpendicular to) the smectic density wave vector direction, rather than $\ensuremath{\delta}$ function peaks. Observation of these phenomena requires very high instrumental resolution together with a resolution function with wings which drop off much more rapidly than ${q}_{\ensuremath{\parallel}}^{\ensuremath{-}2}({q}_{\ensuremath{\perp}}^{\ensuremath{-}4})$. We show that these requirements may be met by using a three crystal x-ray spectrometer with multiple-reflection channel cut crystals as monochromator and analyzer. We find that the smectic-$A$ Bragg peaks observed in the liquid-crystal octyloxy-cyanobiphenyl are indeed consistent with the predicted power-law singularity form. Furthermore, the explicit values of $\ensuremath{\eta}$ required to describe the measured profiles are in accordance with calculations of $\ensuremath{\eta}$ using the harmonic approximation with empirically determined splay and layer compressibility elastic constants.

Non-linear dielectric properties of aluminium/monomolecular layers of calcium behenate/aluminium structures

We studied the non-linear dielectric properties of aluminium/monomolecular layers of calcium behenate/aluminium structures at high electric induction ( D > 10 −3 C m −2). These properties generally arise from the motion of electric charges that are trapped in both the alumina at the surface of the electrodes and in the monolayers and result in a hyperpolarizability. However, in some particular cases in which dipolar relaxation mechanisms were present we observed a decrease in the polarizability. This decrease is due to a Langevin-Debye-type saturation at high electric field. Since the mechanical compressibility of the monomolecular layers is small (1.6 × 10 −10 N m −2), electrostatic compressibility and the electrostriction phenomena are of minor importance. The introduction of small quantities of water produces a marked increase in the non-linear phenomena which may mask all the other phenomena.

Water Drive From Interbedded Shale Compaction In Superpressured Gas Reservoirs A Model Study

The behavior of abnormally high-pressured gas reservoirs in sand formations with randomly interbedded, thin, noncontinuous shale layers is examined using numerical simulation. The relevance of the internal water drive resulting from shale compaction and the influence of mobile water generation on reservoir and well behavior are discussed. Introduction An increasing number of hydrocarbon reservoirs discovered at great depths have pressures that are significantly higher than the hydrostatic pressure. Because of the high temperatures found at great depths, a large percentage of these superpressured reservoirs are gas or percentage of these superpressured reservoirs are gas or gas-condensate types. Several authors discussed the conditions that help create superpressured reservoirs. Such reservoirs often are found in thick sedimentary basins characterized by high-velocity sedimentation. Tightly interbedded shale and sand layers (under impermeable layers) are typical of superpressured reservoirs. The compressibility of abnormally high-pressured formations is higher than normal resulting from their understressed condition. When the abnormally high-pressured formation is a hydrocarbon reservoir, the high rock compressibility and even higher compressibility of the shale layers, either interbedded or boundary, may contribute appreciably to reservoir energy. Purpose Purpose It long has been recognized that reservoir rock compaction as well as interstitial water expansion, both resulting from pressure depletion, can contribute appreciably to the energy supporting production in abnormally high-pressured gas reservoirs. Several authors pointed out that in reservoirs embedded between thick shale layers, a sensible contribution to the production mechanism may originate by water expelled from the confining shale layers. Because these shale layers are very thick, the time required for the decreasing reservoir pressure to diffuse throughout the shale body may be more than the productive life of the reservoir. When reservoir rock contains very thin, noncontinuous shale layers, randomly distributed within the sand body, the time delay for water release from interbedded shale compaction can be disregarded. Wallace presented a list of actual gas reservoirs where water released presented a list of actual gas reservoirs where water released from the compaction of interbedded shale layers did contribute relevantly to reservoir drive, thus creating what might be termed an "internal water drive." In this study, production behavior of abnormally high-pressured gas reservoirs with thin shale interbeddings was examined. The study aimsto evaluate the energy contribution to reservoir drive resulting from water released from interbedded shale compaction; andto gain information about the adverse influence that diffused generation of mobile water (resulting from shale compaction) may have on well performance, considering that water production in gas wells poses disposal and often difficult lifting problems . JPT P. 937

Turbulent Near Wake of G Fiat Plate : Part 2, Effects of Boundary Layer Profile and Compressibility

In the previous report, we proposed a method to calculate the development of the incompressible turbulent wake close to a flat plate. The calculated results were compared with experimental data in which the wake started from the turbulent boundary layers on both sides of a thin flat plate. The agreement between the calculated and the experimental results was very good, and we can conclude that the diffusion phenomenon of the turbulent near wake has been made clear both qualitatively and quantitatively. In that case the shape parameters of the boundary layers at the trailing edge of the plate were all equal to 1.45. Here in this report, we extend the previous method so that we can study the effect of the boundary layer profile and that of compressibility upon the development of the turbulent wake close to a flat plate. The calculated results show that the wake profiles is dependent on the boundary layer profile and compressibility. The agreement between the calculated and the experimental results is excellent.

Lubricant film thickness and wear in rolling point contact : T. E. Tallian, E. F. Brady, J. I. McCool and L. B. Sibley, ASLE Trans., 8 (1965) 411–424

A numerical solution to the elastohydrodynamic lubrication problem of a rigid cylinder and an elastic layer firmly bonded to a rigid substrate in normal approach and separated by a fluid of constant viscosity is presented. The rate of change of the deformation with time was neglected in the present investigation. The governing equations were solved via an iterative method in order to compute the pressure distribution and the corresponding film profile.Influences of the layer thickness, the layer compressibility and the central squeeze-film velocity on the results were investigated. In the case of the Hertzian contact, the present method was validated against the results reported in Herrebrugh [Elastohydrodynamic squeeze films between two cylinders in normal approach, Trans ASME, J Lubric Technol Ser F 1970; 92:292–302] where the results showed a very good agreement.

Some effects of compressibility on the indentation of a thin elastic layer by a smooth rigid cylinder

A truncated cosine series solution to the integral equation for the pressure distribution is evaluated using a digital computer. Tables of results are given which allow the calculation of pressure distribution, tangential surface strain and indentation under load when the contact width is less than four times the layer thickness. Calculations derived from these results are given, which show the effect of layer compressibility.