New conductivity probes for dispersivity measurements in porous media

The new electric probes described in this note are fabricated using printed circuit techniques. They offer various advantages over the existing models: high miniaturization, small disturbance of the porous medium, precise location, low cost and easy fabricatio     

The flow of a dielectric liquid

The nature of the forces acting on a dielectric liquid in an electric field in the presence of a temperature gradient is investigated. It is shown that the electrical forces produced by nonuniformity in the electrical conductivity of the medium can give rise to a hydrodynamic flow.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 136–137, November–December, 1973.     

INSTABILITY AND DISPERSIVITY OF WAVE PROPAGATION ININELASTIC SATURATED/UNSATURATED POROUS MEDIA

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｔｒａｎｓｉｅｎｔｐｈｅｎｏｍｅｎａｏｆｄｙｎａｍｉｃｐｒｏｂｌｅｍｓａｎｄｔｈｅｍａｎｎｅｒｓｔｏｔｒｅａｔｔｈｅｍａｒｅｇｅｎｅｒａｌｌｙｒｅｌａｔｅｄｔｏｔｈｅｓｐｅｃｔｒａｌｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｅｘｃｉｔａｔｉｏｎ .Ｏｎｅｍａｙｏｍｉｔｐｒｏｐａｇａｔｉｎｇｗａｖｅｓｉｆｒｅｌａｔｉｖｅｌｙｌｏｗｅｒｆｒｅｑｕｅｎｃｉｅｓｇｏｖｅｒｎｔｈｅｒｅｓｐｏｎｓｅｓｉｎｔｈｅｐｒｏｂｌｅｍｓｓｕｃｈａｓｓｅｉｓｍｉｃｒｅｓｐｏｎｓｅｓａｎｄｒｅｓｐｏｎ…     

The flow of a non-Newtonian liquid near a rotating disk

Synopsis The flow of non-Newtonian liquid near a rotating disk has been discussed by using second order stress strain velocity relations of classical hydrodynamics. It is found that the effect of cross-viscosity depends on a non-dimensional number R _c. The boundary layer thickness decreases and the dimensionless moment coefficient increases with the increase of R _c.     

The shape of a vertically falling stream of a Newtonian liquid

Summary The diameters of the axially symmetric streams of two Newtonian liquids of different viscosities falling vertically under gravity have been measured as a function of the distance from the nozzle. The measurements have been compared with two theories, (I, II) based on different approximations. Theory I leads to a second-order ordinary differential equation and theory II gives an asymptotic solution of theNavier-Stokes equations. It was found that the first approach was sufficient to explain the measurements in the high viscosity liquid (30,000 cS) but the asymptotic solution was needed to explain the low viscosity (1,000 cS) measurements.

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Zusammenfassung Die Durchmesser der achsensymmetrischen Str?mungen zweier newtonischer Flüssigkeiten verschiedener Viskosit?ten, die unter ihrem Eigengewicht senkrecht austreten, werden als Funktion des Abstandes von einer Düse gemessen. Die Messungen werden mit zwei Theorien (I, II) verglichen, die auf verschiedene N?herungen beruhen. Die Theorie I führt auf eine gew?hnliche Differentialgleichung zweiter Ordnung, w?hrend die Theorie II eine asymptotische L?sung derNavier-Stokes-Gleichung ergibt. Es zeigt sich, da? die erste N?herung ausreicht, um die Messungen der hochviskosen Flüssigkeit (30.000 cS) zu beschreiben. Zur Erl?uterung der Messungen des niedrig-viskosen Silikon?ls (1.000 cS) bedarf es der asymptotischen L?sung.

     

Self-similar thinning of a liquid film separating liquid phases or a liquid and a solid phase

The article discusses the thinning of a thin flat film of liquid between coalescing bubbles or coalescing drops due to motion of the liquid under the action of capillary forces, under drag conditions of the surfaces of the film. A study was also made of the outflow of a liquid from a film separating a bubble (drop) from a solid surface. The problem of the decrease in thickness and subsequent breakaway of thin liquid films is of interest in investigations of the kinetics of coalescence and coagulation and in the theory of the stability of foams and lyophobic colloids in the presence of surfactants or electrolytes, as well as in the theory of heterogeneous boiling. Information on some work and on special characteristics of the statement of the problem may be found in [1].Translated from Izvestiya Akademii Nauk SSSR. Mekhanika Zhidkosti i Gaza, No. 2, pp, 39–48, March–April, 1973.     

The flow of a power-law liquid in a continuous-flow squeeze film

Consideration is given to the flow of an inelastic ‘power-law’ liquid in a continuous flow squeeze film. This simulates the flow in a conventional squeeze film by continuously injecting fluid into the narrow gap between two plates through the lower plate (Oliver et al. [6]). To zero order in the usual lubrication approximation the results are identical with those for the conventional squeeze film. To first order, useful corrections to the normal force due to the effects of inertia are obtained.     

Relevance of a thermal contact resistance depending on the solid/liquid phase change transition for sprayed composite metal/ceramic powder by direct current plasma jets

The thermal contact between layers plays a key role in the behaviour of composite particles (mechanofused) subjected to a high temperature jet (example of two layers metal/ceramic particles under plasma spraying). This work underlines the interest of considering a thermal contact resistance varying with the melting state of the two components along the full process. The computational model considers the time-dependent state of the particle during its flight with coupled transfers and solid/liquid/vapor phase changes. To cite this article: M. Bouneder et al., C. R. Mecanique 336 (2008).     

The breakup and atomization of a viscous liquid jet

Based on the linear analysis of stability, a dispersion equation is deduced which delineates the evolution of a general 3-dimensional disturbance on the free surface of an incompressible viscous liquid jet. With respect to the spatial growing disturbance mode, the numerical results obtained from the solution of the dispersion equation reveal that a dimensionless parameterJ _e exists. AsJ _e>1, the axisymmetric disturbance mode is most unstable; and whenJ _e<1, the asymmetric disturbances come into being, their growth rate increases with the decrease, ofJ _e, till one of them becomes the most unstable disturbance. The breakup of a low-speed liquid jet results from the developing of axisymmetric disturbances, whose instability is produced by the surface tension; while the atomization of a high-speed liquid jet is brought about by the evolution of nonaxisymmetric disturbance, whose instability is caused by the aerodynamic force on the interface between the jet and the ambient gas. The project supported by the National Natural Science Foundation of China     

The added mass of a deformable cylinder moving in a liquid

Let an infinitely long cylinder move perpendicular to its length in an infinite mass of liquid which is at rest at infinity. If the cylinder is rigid, the whole effect of the presence of the liquid may be represented by adding to the inertia per unit length of the solid cylinder the mass per unit length of the displaced fluid. If, however, the cylinder is elastically deformable, the mass of the moving fluid depends on the change in shape of the, initially circular, cross-sections of the cylinder. Thus the added mass is no longer a constant, but a function of the pressure exerted by the fluid on the solid cylinder.     

The characteristics of inertial resonances in a rotating liquid

Devoted to the memory of Valery Fedorovich Tarasov, close colleague and teacher.     

Steady rise of a liquid drop in a viscous liquid

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 1, pp. 78–88, January–February, 1992.     

Slow motions of a liquid drop in a viscous liquid

The problem of the fully established slow translational motion of a round drop (bubble) in a viscous liquid was solved by Adamar and Rybchinskii [1, 2]. The results of experimental measurements are rarely in agreement with the Adamar-Rybchinskii formula. This is connected with braking of the flow due to surface-active impurities, which are usually rather numerous in liquids. Nevertheless, we shall consider the problem of the not fully established motion of a drop in the simplest case, assuming that there are no surface-active substances. The article discusses problems of the vibrations and motions of a spherical drop in a viscous liquid, with arbitrary accelerations. An analysis is made of a formula for the force of resistance of a drop of liquid with a high viscosity, an elastoviscous drop, and a particle with slipping-through.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 32–37, November–December, 1975.     

Phenomena of a liquid drop falling to a liquid surface

Two kinds of phenomenon have been observed when a liquid drop falls to a surface of the same liquid. The first, which can nearly always be observed, involves splash and some degree of penetration and cleavage and the conditions for this occurrence are identified. The experimental observations are compared with previous computational results. The second kind of colliding phenomena can be observed only by chance in an ordinary falling drop experiment and appears to be random. It includes the two phenomena investigated in this paper: the floating drop and the rolling drop.     

The generation of a draining liquid film by the vertical withdrawal of a flat plate from an elastico-viscous liquid

The analysis of Waters and Keeley [1] for the start-up of the drainage of an elastico-viscous liquid from a vertical surface is extended to include the effect of the vertical surface moving vertically with an arbitrary velocity. This is used to examine the effect of elasticity on the interesting drainage problems associated with the sudden withdrawal of a vertical plate from an elastico-viscous liquid.     

The untwisting of a bounded sample of cholesteric liquid crystal

This article is a theoretical investigation of the untwisting of a cholesteric liquid crystal in a bounded sample with strong anchoring due to an applied magnetic field. Continuum theory and energy comparisons are used to determine graphically the form of the untwisting prior to and including the transition to the nematic phase.     

Control of a liquid–liquid heat exchanger

 The analytical solutions of equations describing the dynamics of distributed parameter systems are usually complicated in form and derivations and inconvenient to use for simulation and control system design. The liquid–liquid counter flow heat exchanger is an example of these disturbed parameter systems. An analytical solution of the dynamics of a symmetrically operated counter flow heat exchanger in the form of transfer function matrix is investigated in open-loop and close-loop conditions. The resulting non-linear model was linearized using perturbation approach. A feed-forward path controller to counteract at any disturbances in the boundary temperature and a non-interactive controller to decouple the outputs were implemented. Received on 22 February 2001 / Published online: 29 November 2001     

The load-bearing capacity of a continuous-flow squeeze film of liquid

A new form of squeeze film system is described in which the movement of one plate towards the other is simulated by the continuous volume generation of liquid over the plate area. The liquid exudes from 1580 holes distributed uniformly over the lower plate surface. An advantage of the system is that there are no moving parts, but it is important to evaluate the device using Newtonian liquids in order to compare the load bearing capacity with that predicted by equations developed for orthodox squeeze film systems. Liquid maldistribution is shown to be a problem which may be solved in various ways, one of which is to ensure that the pressure drop through the plate is high relative to that in the squeeze film.Results obtained using Newtonian liquids make satisfactory comparison with theoretical predictions, though liquid inertia probably makes a lower contribution to load bearing than is the case for an orthodox squeeze film. Liquid maldistribution is allowed for on a theoretical basis or corrected by the use of a distributor plate placed below the perforated surface.Preliminary tests using viscoelastic solutions (based on polyacrylamide of high molecular weight) suggest that the load bearing properties of the squeeze film are significantly enhanced. A load 600 per cent greater than the theoretical load is obtained in one case, the suggestion being made that this is due to stress of viscoelastic origin.Nomenclature D Exit diameter of holes in spinnerette - F ₁ to F ₆ Vertical force on top plate due to flow in squeeze film, defined by (1), (8), (11), (12), (13) and (14) respectively - h Plate separation - h _L Distance of distributor plate from lower surface of spinnerette (function of r) - I ₀ Modified Bessel function of first kind, order 0 - I ₁ Modified Bessel function of first kind, order 1 - K ₀ Modified Bessel function of second kind, order 0 - L Length of hole, based on diameter D, giving same pressure drop as actual spinnerette holes - dm/dt Mass flowrate of liquid - N Total number of holes in spinnerette (1580) - p Isotropic pressure in squeeze film - P _RES Isotropic pressure in reservoir behind lower plate of spinnerette - p–P _RES - (dp/dr)_s Pressure gradient in squeeze film - (dp/dr)_L Pressure gradient in lower film below spinnerette when distributor plate is used - Q Total liquid volume flowrate - q _s Volume flowrate through squeeze film at radius r - q _L Volume flowrate through lower film at radius r - r radial coordinate - R radius of upper disc - - v Velocity of upper disc relative to lower one (simulated by Q/R ² in continuous flow system) - V _R Average radial liquid velocity at radius R - V _S Liquid exit velocity from single hole - V _r V V _z Point velocity components in r, and z directions respectively - z Axial coordinate - Parameter in (8) (3ND ⁴/32LR ² h ³) - Viscosity of liquid - Density of liquid - _rz Shear stress