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Liquid Bridge (liquid + bridge)

Distribution by Scientific Domains

Chemistry	60%
Engineering	40%

Selected Abstracts

Influence of liquid bridges on the mechanical behaviour of polydisperse granular materials

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2006
F. Soulié
Abstract We investigate a polydisperse granular material in which the particle interactions are governed by a capillary force law. The cohesion force for a grain-pair with unequal diameters is expressed as an explicit function of the inter-particle distance and the volume of the liquid bridge. This analytical relation is validated by experiments on a reference material. Then, it is completed by a rupture criterion and cast in the form of a force law that accounts for solid contact, capillary force and rupture characteristics of a grain-pair. Finally, in order to evaluate the influence of capillary cohesion on the macroscopic behaviour, radial and axial compression tests on cylindrical assemblies of wet particles are simulated using a 3D distinct element method. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Capillary forces between two solid spheres linked by a concave liquid bridge: Regions of existence and forces mapping

AICHE JOURNAL, Issue 5 2009
David Megias-Alguacil
Abstract This article focuses on the capillary interactions arising when two spherical particles are connected by a concave liquid bridge. This scenario is found in many situations where particles are partially wetted by a liquid, like liquid films stabilized with nanoparticles. We analyze different parameters governing the liquid bridge: interparticle separation, wetting angle and liquid volume. The results are compiled in a liquid volume-wetting angle diagram in which the regions of existence (stability) or inexistence (instability) of the bridge are outlined and the possible maximum and minimal particle distances for which the liquid bridge may be found. Calculations of the capillary forces discriminate those conditions for which such force is repulsive or attractive. The results are plotted in form of maps that allow an easy understanding of the stability of a liquid bridge and the conditions at which it may be produced for the two particle model. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Agglomeration modeling of small and large particles by a diffusion theory approach

AICHE JOURNAL, Issue 5 2009
Alvaro Realpe
Abstract The interaction particle-binder during the wet granulation process plays a major role in the agglomeration of particles. This interaction has been modeled by a force balance acting on the particle where the binder's viscous force increases the strength of liquid bridge and facilitates the particle agglomeration. In this work, agglomeration kernels based on Brownian movement approach of small particles in the binder layer, the size ratio between particles (monodispersed and polydispersed), and binder's viscous forces were considered to model the wet granulation process of pharmaceutical powders in a laboratory-scale high shear mixer. The assumptions of no-stationary and pseudostationary behavior were suitable to describe the growth kinetics of the two stages (fast and slow) observed. A volume ratio of 150 between large and small particles produces the most effective granulation growth. The developed kernels were tested simulating experimental data obtained from a high shear mixer. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Influence of moisture content on measurement accuracy of porous media thermal conductivity

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2009
Mingzhi Yu
Abstract The thermal conductivity measurement accuracy of sand was experimentally studied with a hot disk thermal constant analyzer and water morphologies, distribution, and evolution at the pore scale were observed with a charge coupled device (CCD) combined with a microscope. It was found that thermal conductivities of samples with low moisture content (<25%) could not be accurately measured. For samples with low moisture content, the analysis showed that the water in the region adjacent to the analyzer sensor mainly existed as isolated liquid bridges between/among sand particles and would evaporate and diffuse to relatively far regions because of being heated by the sensor during measurement. Water evaporation and diffusion caused the sample constitution in the region adjacent to the sensor to vary throughout the whole measurement process, and accordingly induced low accuracy of the obtained thermal conductivities. Due to high water connectivity in pores, the rate of water evaporation and diffusion in porous media of high moisture content was relatively slow when compared with that of low moisture content. Meanwhile, water in the relatively far regions flowed back to the region adjacent to the sensor by capillary force. Therefore, samples consisting of the region adjacent to the sensor maintained the constant and thermal conductivities of porous media with relatively high moisture content and could be measured with high accuracy. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20272 [source]

Micromechanical aspects of the shear strength of wet granular soils

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2008
U. El Shamy
Abstract This paper presents a micromechanical model for the analysis of wet granular soils at low saturation (below 30%). The discrete element method is employed to model the solid particles. The capillary water is assumed to be in a pendular state and thus exists in the form of liquid bridges at the particle-to-particle contacts. The resulting inter-particle adhesion is accounted for using the toroidal approximation of the bridge. Hydraulic hysteresis is accounted for based on the possible mechanism of the formation and breakage of the liquid bridges during wetting and drying phases. Shear test computational simulations were conducted at different water contents under relatively low net normal stresses. The results of these simulations suggest that capillary-induced attractive forces and hydraulic hysteresis play an important role in affecting the shear strength of the soil. These attractive forces produce a tensile stress that contributes to the apparent cohesion of the soil and increases its stiffness. During a drying phase, capillary-induced tensile stresses, and hence shear strength, tend to be larger than those during a wetting phase. The proposed model appears to capture the macroscopic response of wet granular materials and revealed a number of salient micromechanical mechanisms and response patterns consistent with theoretical considerations. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Influence of liquid bridges on the mechanical behaviour of polydisperse granular materials

Characterization of granular flow of wet solids in a bladed mixer

AICHE JOURNAL, Issue 8 2006
Azzeddine Lekhal
Abstract In this study, we measure instantaneous, average, and fluctuating velocity fields at exposed surfaces for dry and wet grains in a vertical cylindrical mixer, agitated by four pitched blades. When the material is dry, the free surface of the granular bed deforms, rising where the blades are present, and falling between blade passes. Although average velocities are predominantly azimuthal, instantaneous velocities tracked in time reveal three-dimensional particle circulations, including significant periods of particle motion in the opposite direction to that of the blades, indicative of bed penetration. When moisture is added to the solid particles, the flow dynamics change from a regime dominated by the motion of individual grains to a regime controlled by the motion of small clumps that form as a result of the cohesive forces. This transition is characterized by a reduced particle,particle collision frequency and exhibits a sharp decrease in the granular temperature at the free surface. This transition is also characterized by an increase in bed porosity, which is attributed to increased cohesiveness arising from liquid bridges. A Fourier transform analysis conducted on the tangential component of the velocities (dominant flow) shows that a group of high frequencies exceeding the blade rotation frequency become significant with added moisture. These are characteristics of the large number of wet agglomerates flowing between successive blade passes. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

On the Thermodynamic Stability of Liquid Capillary Bridges

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2007
Janet Aw Elliott
Abstract Capillary condensation is important in the behaviour of various materials encountered in nature and in industrial processes. The behaviour of liquid capillary bridges has mostly been investigated from a mechanical perspective, with an emphasis on computing the relevant adhesion forces. In the present paper, a thermodynamic approach is used, computing the free energy of such systems (based on numerically constructed shapes of liquid bridges) in order to determine the nature and properties of their equilibrium states. The dependence of the thermodynamic equilibrium configurations on the geometry of the system is investigated, and comparisons are made with experimental findings reported in the literature. La condensation capillaire est importante dans le comportement de divers matériaux rencontrés dans la nature et dans les procédés industriels. Le comportement des ponts capillaires liquides a surtout été étudié d'un point de vue mécanique, l'accent étant mis sur le calcul par ordinateur des forces d'adhésion pertinentes. Dans le présent article, on utilise une approche thermodynamique utilisant le calcul par ordinateur de l'énergie libre de tels systèmes (d'après les formes numériquement construites des ponts liquides), dans le but de déterminer la nature et les propriétés de leurs états d'équilibre. La dépendance des configurations d'équilibre thermodynamique sur la géométrie du système est étudiée, et des comparaisons sont faites avec les résultats expérimentaux présentés dans la littérature scientifique. [source]