The Experts below are selected from a list of 402 Experts worldwide ranked by ideXlab platform
Michael J Buckingham - One of the best experts on this subject based on the ideXlab platform.
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on pore fluid viscosity and the wave properties of saturated granular materials including marine sediments
Journal of the Acoustical Society of America, 2007Co-Authors: Michael J BuckinghamAbstract:The grain-shearing (GS) theory of wave propagation in a saturated granular material, such as a marine sediment, is extended to include the effects of the viscosity of the molecularly thin layer of pore fluid separating contiguous grains. An equivalent mechanical system consisting of a saturating, strain-hardening dashpot in series with a Hookean Spring represents the intergranular interactions. Designated the VGS theory, the new model returns dispersion curves that differ mildly from those of the GS theory at lower frequencies, below 10kHz, where effects due to the viscosity of the pore fluid may be non-negligible. At higher frequencies, the VGS dispersion curves approach those of the GS theory asymptotically. The VGS theory is shown to match the SAX99 dispersion curves reasonably well over the broad frequency band of the measurements, from 1 to 400kHz. This includes the frequency regime between 1 and 10kHz occupied by Schock’s chirp sonar data, where the viscosity of the pore fluid appears to have a disc...
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on pore fluid viscosity and the wave properties of saturated granular materials including marine sediments
Journal of the Acoustical Society of America, 2007Co-Authors: Michael J BuckinghamAbstract:The grain-shearing (GS) theory of wave propagation in a saturated granular material, such as a marine sediment, is extended to include the effects of the viscosity of the molecularly thin layer of pore fluid separating contiguous grains. An equivalent mechanical system consisting of a saturating, strain-hardening dashpot in series with a Hookean Spring represents the intergranular interactions. Designated the VGS theory, the new model returns dispersion curves that differ mildly from those of the GS theory at lower frequencies, below 10 kHz, where effects due to the viscosity of the pore fluid may be non-negligible. At higher frequencies, the VGS dispersion curves approach those of the GS theory asymptotically. The VGS theory is shown to match the SAX99 dispersion curves reasonably well over the broad frequency band of the measurements, from 1 to 400 kHz. This includes the frequency regime between 1 and 10 kHz occupied by Schock's chirp sonar data, where the viscosity of the pore fluid appears to have a discernible effect on the dispersion curves.
L E Scrive - One of the best experts on this subject based on the ideXlab platform.
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deformable roll coating flows steady state and linear perturbation analysis
Journal of Fluid Mechanics, 1997Co-Authors: Marcio S Carvalho, L E ScriveAbstract:Roll coating is distinguished by the use of one or more gaps between rotating cylinders to meter a continuous liquid layer and to apply it to a continuous flexible substrate. Of the two rolls that make a forward or reverse roll coating gap, one is often covered by a layer of more-or-less deformable elastomer. Liquid carried into the converging side of the nip can develop high enough pressure to deform the resilient cover, which changes the nip profile and thus alters the velocity and pressure field. This elastohydrodynamic coupled action is not yet well understood. Theoretical modelling has to take into account the viscous flow, the roll deformation and the free-surface effects in order to predict the flow behaviour. In this work the flow between a rigid and a deformable counter-rotating roll that shares the same angular speed is described by the lubrication approximation together with a viscocapillary model, based in the film-flow equation, for the film-split region. The deformation of the elastomer layer is modelled by Hookean Springs oriented radially, which constitute a one-dimensional model. The stability of the system to transverse perturbation is analysed by examining the time-dependent response to infinitesimal disturbances in order to identify those that grow fastest. The corresponding system of equations is solved by Newton's method with first-order continuation. The relationship between coating thickness, operational parameters (loading force, gap setting, roll velocities, etc.), liquid properties and the properties of the cover is reported, as well as the critical capillary number for onset of ribbing and wavelengths of the ribbing pattern predicted by the mathematical model. The results indicate how a deformable cover may be used in order to delay the onset of ribbing for a desired coating thickness. In order to validate the theoretical predictions of the viscocapillary/Hookean Spring model, the symmetric film-split flows between a pair of rigid rolls and a pair consisting of a deformable roll and a rigid one were also analysed experimentally.
Marcio S Carvalho - One of the best experts on this subject based on the ideXlab platform.
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deformable roll coating flows steady state and linear perturbation analysis
Journal of Fluid Mechanics, 1997Co-Authors: Marcio S Carvalho, L E ScriveAbstract:Roll coating is distinguished by the use of one or more gaps between rotating cylinders to meter a continuous liquid layer and to apply it to a continuous flexible substrate. Of the two rolls that make a forward or reverse roll coating gap, one is often covered by a layer of more-or-less deformable elastomer. Liquid carried into the converging side of the nip can develop high enough pressure to deform the resilient cover, which changes the nip profile and thus alters the velocity and pressure field. This elastohydrodynamic coupled action is not yet well understood. Theoretical modelling has to take into account the viscous flow, the roll deformation and the free-surface effects in order to predict the flow behaviour. In this work the flow between a rigid and a deformable counter-rotating roll that shares the same angular speed is described by the lubrication approximation together with a viscocapillary model, based in the film-flow equation, for the film-split region. The deformation of the elastomer layer is modelled by Hookean Springs oriented radially, which constitute a one-dimensional model. The stability of the system to transverse perturbation is analysed by examining the time-dependent response to infinitesimal disturbances in order to identify those that grow fastest. The corresponding system of equations is solved by Newton's method with first-order continuation. The relationship between coating thickness, operational parameters (loading force, gap setting, roll velocities, etc.), liquid properties and the properties of the cover is reported, as well as the critical capillary number for onset of ribbing and wavelengths of the ribbing pattern predicted by the mathematical model. The results indicate how a deformable cover may be used in order to delay the onset of ribbing for a desired coating thickness. In order to validate the theoretical predictions of the viscocapillary/Hookean Spring model, the symmetric film-split flows between a pair of rigid rolls and a pair consisting of a deformable roll and a rigid one were also analysed experimentally.
Özarslan Evren - One of the best experts on this subject based on the ideXlab platform.
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Magnetic resonance assessment of effective confinement anisotropy with orientationally-averaged single and double diffusion encoding
'Springer Science and Business Media LLC', 2021Co-Authors: Yolcu Cem, Herberthson Magnus, Westin Carl-fredrik, Özarslan EvrenAbstract:Porous or biological materials comprise a multitude of micro-domainscontaining water. Diffusion-weighted magnetic resonance measurements are sensitive to the anisotropy of the thermal motion of such water. This anisotropy can bedue to the domain shape, as well as the (lack of) dispersion in their orientations.Averaging over measurements that span all orientations is a trick to suppress thelatter, thereby untangling it from the influence of the domains’ anisotropy on thesignal. Here, we consider domains whose anisotropy is modeled as being the resultof a Hookean (Spring) force, which has the advantage of having a Gaussian diffusionpropagator while still confining the spatial range for the diffusing particles. In fact,this confinement model is the effective model of restricted diffusion when diffusion isencoded via gradients of long durations, making the model relevant to a broad rangeof studies aiming to characterize porous media with microscopic subdomains. In thisstudy, analytical expressions for the powder-averaged signal under this assumptionare given for so-called single and double diffusion encoding schemes, which sensitize the MR signal to the diffusive displacement of particles in, respectively, one ortwo consecutive time intervals. The signal for one-dimensional diffusion is shownto exhibit power-law dependence on the gradient strength while its coefficient bearssignatures of restricted diffusion.Funding agencies: : Swedish Foundation for Strategic Research AM13-0090, the Swedish Research Council 2016-04482, Linköping University Center for Industrial Information Technology (CENIIT), VINNOVA/ITEA3 17021 IMPACT, and National Institutes of Health P41EB015902 and R01MH074794.
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Magnetic resonance assessment of effective confinement anisotropy with orientationally-averaged single and double diffusion encoding
2019Co-Authors: Yolcu Cem, Herberthson Magnus, Westin Carl-fredrik, Özarslan EvrenAbstract:Porous or biological materials comprise a multitude of micro-domains containing water. Diffusion-weighted magnetic resonance measurements are sensitive to the anisotropy of the thermal motion of such water. This anisotropy can be due to the domain shape, as well as the (lack of) dispersion in their orientations. Averaging over measurements that span all orientations is a trick to suppress the latter, thereby untangling it from the influence of the domains' anisotropy on the signal. Here, we consider domains whose anisotropy is modeled as being the result of a Hookean (Spring) force, which has the advantage of having a Gaussian diffusion propagator while still retaining the fact of finite spatial range for the diffusing particles. Analytical expressions for the powder-averaged signal under this assumption are given for so-called single and double diffusion encoding schemes, which sensitize the MR signal to the diffusive displacement of particles in, respectively, one or two consecutive time intervals.Comment: 12 pages, 3 figure
Yahiaoui Ghozlane - One of the best experts on this subject based on the ideXlab platform.
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McKean-Vlasov diffusion and the well-posedness of the Hookean bead-Spring-chain model for dilute polymeric fluids: small-mass limit and equilibration in momentum space
2018Co-Authors: Süli Endre, Yahiaoui GhozlaneAbstract:We reformulate a general class of classical bead-Spring-chain models for dilute polymeric fluids, with Hookean Spring potentials, as McKean-Vlasov diffusion. This results in a coupled system of partial differential equations involving the unsteady incompressible linearized Navier-Stokes equations, referred to as the Oseen system, for the velocity and the pressure of the fluid, with a source term which is a nonlinear function of the probability density function, and a second-order degenerate parabolic Fokker-Planck equation, whose transport terms depend on the velocity field, for the probability density function. We show that this coupled Oseen-Fokker-Planck system has a large-data global weak solution. We then perform a rigorous passage to the limit as the masses of the beads in the bead-Spring-chain converge to zero, which is shown in particular to result in equilibration in momentum space. The limiting problem is then used to perform a rigorous derivation of the Hookean bead-Spring-chain model for dilute polymeric fluids, which has the interesting feature that, if the flow domain is bounded, then so is the associated configuration space domain and the associated Kramers stress tensor is defined by integration over this bounded configuration domain.Comment: 85 page