The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Wesley W. Wallender - One of the best experts on this subject based on the ideXlab platform.
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effects of adsorbed water layer in predicting saturated hydraulic conductivity for clays with kozeny carman equation
Journal of Geotechnical and Geoenvironmental Engineering, 2008Co-Authors: Purnendu N Singh, Wesley W. WallenderAbstract:Saturated hydraulic conductivity for clays predicted using the conventional Kozeny–Carman equation is scalar and found to diverge significantly from measured values. The divergence is consistent and systematic requiring a mathematical derivation of the formula using first principles. The incorporation of the physical characteristics of the adsorbed water layer surrounding a clay particle results in a generalized Kozeny–Carman equation with two new parameters. The porosity correction factor gives the effective porosity taking into account the thickness of the adsorbed water layer and the mass specific surface area of the clay. The second parameter is shown to depend on the Interparticle Contact area and the Interparticle Contact stress. The ability of the proposed physically based generalized Kozeny–Carman equation to explain the results from some of the published laboratory permeability tests is tested. The paper results in a new theoretical framework to model changes in saturated hydraulic conductivity i...
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Effects of Adsorbed Water Layer in Predicting Saturated Hydraulic Conductivity for Clays with Kozeny — Carman Equation
Journal of Geotechnical and Geoenvironmental Engineering, 2008Co-Authors: Purnendu N Singh, Wesley W. WallenderAbstract:Saturated hydraulic conductivity for clays predicted using the conventional Kozeny–Carman equation is scalar and found to diverge significantly from measured values. The divergence is consistent and systematic requiring a mathematical derivation of the formula using first principles. The incorporation of the physical characteristics of the adsorbed water layer surrounding a clay particle results in a generalized Kozeny–Carman equation with two new parameters. The porosity correction factor gives the effective porosity taking into account the thickness of the adsorbed water layer and the mass specific surface area of the clay. The second parameter is shown to depend on the Interparticle Contact area and the Interparticle Contact stress. The ability of the proposed physically based generalized Kozeny–Carman equation to explain the results from some of the published laboratory permeability tests is tested. The paper results in a new theoretical framework to model changes in saturated hydraulic conductivity i...
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Effective Stress from Force Balance on Submerged Granular Particles
International Journal of Geomechanics, 2007Co-Authors: Purnendu N Singh, Wesley W. WallenderAbstract:A new equation for effective stress is derived from a physically based approach of force balance on submerged granular particles. The Euler cut principle and the Euler’s first law of mechanics are used to analyze the Interparticle Contact stress in a fluid saturated porous media. The analysis starts from basic principles and provides a detailed derivation of the formulas. Tensor algebra together with Coulomb’s friction law, the mean value theorem and area weighted averaging techniques are used to simplify the mathematical formulation leading to effective stress. A new mathematical constraint, requiring spatially averaged Interparticle Contact stress to be orders of magnitude larger than spatially averaged pore pressure, is presented for the widely used Terzaghi’s effective stress equation.
Purnendu N Singh - One of the best experts on this subject based on the ideXlab platform.
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effects of adsorbed water layer in predicting saturated hydraulic conductivity for clays with kozeny carman equation
Journal of Geotechnical and Geoenvironmental Engineering, 2008Co-Authors: Purnendu N Singh, Wesley W. WallenderAbstract:Saturated hydraulic conductivity for clays predicted using the conventional Kozeny–Carman equation is scalar and found to diverge significantly from measured values. The divergence is consistent and systematic requiring a mathematical derivation of the formula using first principles. The incorporation of the physical characteristics of the adsorbed water layer surrounding a clay particle results in a generalized Kozeny–Carman equation with two new parameters. The porosity correction factor gives the effective porosity taking into account the thickness of the adsorbed water layer and the mass specific surface area of the clay. The second parameter is shown to depend on the Interparticle Contact area and the Interparticle Contact stress. The ability of the proposed physically based generalized Kozeny–Carman equation to explain the results from some of the published laboratory permeability tests is tested. The paper results in a new theoretical framework to model changes in saturated hydraulic conductivity i...
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Effects of Adsorbed Water Layer in Predicting Saturated Hydraulic Conductivity for Clays with Kozeny — Carman Equation
Journal of Geotechnical and Geoenvironmental Engineering, 2008Co-Authors: Purnendu N Singh, Wesley W. WallenderAbstract:Saturated hydraulic conductivity for clays predicted using the conventional Kozeny–Carman equation is scalar and found to diverge significantly from measured values. The divergence is consistent and systematic requiring a mathematical derivation of the formula using first principles. The incorporation of the physical characteristics of the adsorbed water layer surrounding a clay particle results in a generalized Kozeny–Carman equation with two new parameters. The porosity correction factor gives the effective porosity taking into account the thickness of the adsorbed water layer and the mass specific surface area of the clay. The second parameter is shown to depend on the Interparticle Contact area and the Interparticle Contact stress. The ability of the proposed physically based generalized Kozeny–Carman equation to explain the results from some of the published laboratory permeability tests is tested. The paper results in a new theoretical framework to model changes in saturated hydraulic conductivity i...
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Effective Stress from Force Balance on Submerged Granular Particles
International Journal of Geomechanics, 2007Co-Authors: Purnendu N Singh, Wesley W. WallenderAbstract:A new equation for effective stress is derived from a physically based approach of force balance on submerged granular particles. The Euler cut principle and the Euler’s first law of mechanics are used to analyze the Interparticle Contact stress in a fluid saturated porous media. The analysis starts from basic principles and provides a detailed derivation of the formulas. Tensor algebra together with Coulomb’s friction law, the mean value theorem and area weighted averaging techniques are used to simplify the mathematical formulation leading to effective stress. A new mathematical constraint, requiring spatially averaged Interparticle Contact stress to be orders of magnitude larger than spatially averaged pore pressure, is presented for the widely used Terzaghi’s effective stress equation.
A Castellanos - One of the best experts on this subject based on the ideXlab platform.
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rheology of magnetofluidized fine powders the role of Interparticle Contact forces
Journal of Rheology, 2010Co-Authors: M J Espin, M A S Quintanilla, J M Valverde, A CastellanosAbstract:Usually, a bed of solid particles fluidized by a gas is inherently unstable. Gas bubbles are rapidly formed at the onset of fluidization, which hinders the efficiency of gas-solid Contact. In the case of magnetizable particles, gas bubbles may be suppressed by means of an externally applied field that magnetizes the particles. In general, magnetized particles are assumed to behave as point dipoles that organize in chainlike structures oriented along field lines due to dipole-dipole attraction. The physical mechanism responsible for stabilization is, however, unclear. In particular, rheological characterization of magnetically stabilized beds (MSBs) has been a subject of controversy and there is no widely accepted explanation to the empirical fact that magnetofluidized beds (MFBs) can be stabilized by a horizontal field. Several experimental approaches have been used mainly aimed to observe the fluidity of MFBs. Generally, MFBs are reported to behave as a fluid up to a critical magnetic field strength at w...
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Interparticle Contact forces in fine cohesive powders theory and experiments
Pamm, 2003Co-Authors: M A S Quintanilla, A Castellanos, J M ValverdeAbstract:The flow of fine powders is strongly influenced by Interparticle Contact forces. Depending on the Interparticle load force the Contact behavior can be elastic, fully plastic or elasto-plastic. We propose a model for the elasto-plastic loading regime that yields a nonlinear dependence of the Interparticle adhesion force on the Interparticle load force. Interparticle forces are also obtained experimentally. Theoretical results are in reasonable agreement with experimental data.
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correlation between bulk stresses and Interparticle Contact forces in fine powders
Physical Review E, 2001Co-Authors: M A S Quintanilla, A Castellanos, J M ValverdeAbstract:: We present measurements of the tensile strength as a function of the consolidation stress for a set of fine cohesive powders (xerographic toners) of 12.7 microm particle size and with a range of concentration of submicron fumed silica as flow control additive. This additive is well known for its ability to control Interparticle adhesion force. Parallel measurements using an atomic force microscope have been carried out on the adhesion force between two individual grains as a function of a controlled previous load force. The effect of the additive on the tensile strength and adhesion force is analyzed. We have found a good correlation between bulk stresses and adhesion forces between individual particles. This correlation is compatible with the existence of a subnetwork of force chains.
J M Valverde - One of the best experts on this subject based on the ideXlab platform.
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rheology of magnetofluidized fine powders the role of Interparticle Contact forces
Journal of Rheology, 2010Co-Authors: M J Espin, M A S Quintanilla, J M Valverde, A CastellanosAbstract:Usually, a bed of solid particles fluidized by a gas is inherently unstable. Gas bubbles are rapidly formed at the onset of fluidization, which hinders the efficiency of gas-solid Contact. In the case of magnetizable particles, gas bubbles may be suppressed by means of an externally applied field that magnetizes the particles. In general, magnetized particles are assumed to behave as point dipoles that organize in chainlike structures oriented along field lines due to dipole-dipole attraction. The physical mechanism responsible for stabilization is, however, unclear. In particular, rheological characterization of magnetically stabilized beds (MSBs) has been a subject of controversy and there is no widely accepted explanation to the empirical fact that magnetofluidized beds (MFBs) can be stabilized by a horizontal field. Several experimental approaches have been used mainly aimed to observe the fluidity of MFBs. Generally, MFBs are reported to behave as a fluid up to a critical magnetic field strength at w...
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Interparticle Contact forces in fine cohesive powders theory and experiments
Pamm, 2003Co-Authors: M A S Quintanilla, A Castellanos, J M ValverdeAbstract:The flow of fine powders is strongly influenced by Interparticle Contact forces. Depending on the Interparticle load force the Contact behavior can be elastic, fully plastic or elasto-plastic. We propose a model for the elasto-plastic loading regime that yields a nonlinear dependence of the Interparticle adhesion force on the Interparticle load force. Interparticle forces are also obtained experimentally. Theoretical results are in reasonable agreement with experimental data.
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correlation between bulk stresses and Interparticle Contact forces in fine powders
Physical Review E, 2001Co-Authors: M A S Quintanilla, A Castellanos, J M ValverdeAbstract:: We present measurements of the tensile strength as a function of the consolidation stress for a set of fine cohesive powders (xerographic toners) of 12.7 microm particle size and with a range of concentration of submicron fumed silica as flow control additive. This additive is well known for its ability to control Interparticle adhesion force. Parallel measurements using an atomic force microscope have been carried out on the adhesion force between two individual grains as a function of a controlled previous load force. The effect of the additive on the tensile strength and adhesion force is analyzed. We have found a good correlation between bulk stresses and adhesion forces between individual particles. This correlation is compatible with the existence of a subnetwork of force chains.
Stanislav A Medin - One of the best experts on this subject based on the ideXlab platform.
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smoothed particle hydrodynamics using Interparticle Contact algorithms
Journal of Computational Physics, 2002Co-Authors: Anatoly N Parshikov, Stanislav A MedinAbstract:Smoothed particle hydrodynamics (SPH) is a modern effective technique of computer simulation in continuous media mechanics. SPH approximations are quite flexible and allow various constructions. In this paper, Contact interaction between particles is introduced in SPH formulation. The concept is to insert in SPH approximations of a strength medium the velocity and stresses determined at the Contact point by Riemann solution, instead of mean values between velocities and stresses of basic and surrounding particles. In this case, there is no need to use artificial viscosity. In a heat-conducting medium, the Contact temperature is determined by the solution of a thermal discontinuity breakup and heat fluxes in particles are computed with the use of this temperature. The modified SPH approximations easily pass various standard tests and are easily realized in multidimensional codes.
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improvements in sph method by means of Interparticle Contact algorithm and analysis of perforation tests at moderate projectile velocities
International Journal of Impact Engineering, 2000Co-Authors: Anatoly N Parshikov, Stanislav A Medin, Igor I Loukashenko, Valery A MilekhinAbstract:Smooth particle hydrodynamics (SPH) is a new effective technique for impact simulation. SPH approximations are quite flexible and allow various constructions. In this paper Contact interaction between SPH particles described by Riemann solution for normal and tangential discontinuities break-up is introduced in SPH-formulation. The conception is to insert in SPH approximations the velocity and stresses at the Contact surface determined by Riemann solution instead of mean values between velocities and stresses of Contacting basic and surrounding particles. In this case there is no need to use artificial viscosity. Two-dimensional axisymmetrical code for elastoplastic media was created and computations were compared with test data for perforation of steel plate by lead projectile.
