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Suchuan Dong - One of the best experts on this subject based on the ideXlab platform.
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wall bounded multiphase flows of n immiscible incompressible fluids
Journal of Computational Physics, 2017Co-Authors: Suchuan DongAbstract:We present an effective method for simulating wall-bounded multiphase flows consisting of N (N2) immiscible incompressible fluids with different densities, viscosities and pairwise surface tensions. The N-phase physical formulation is based on a modified thermodynamically consistent phase field model that is more general than in a previous work, and it is developed by considering the reduction consistency if some of the fluid components were absent from the system. We propose an N-phase contact-Angle Boundary condition that is reduction consistent between N phases and M phases (2MN1). We also present a numerical algorithm for solving the N-phase governing equations together with the contact-Angle Boundary conditions developed herein. Extensive numerical experiments are presented for several flow problems involving multiple fluid components and solid-wall boundaries to investigate the wettability effects with multiple types of contact Angles. In particular, we compare simulation results with the de Gennes theory for the contact-Angle effects on the liquid drop spreading on wall surfaces, and demonstrate that our method produces physically accurate results.
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on imposing dynamic contact Angle Boundary conditions for wall bounded liquid gas flows
Computer Methods in Applied Mechanics and Engineering, 2012Co-Authors: Suchuan DongAbstract:We present an efficient scheme within the phase field framework for imposing dynamic contact Angle Boundary conditions for wall-bounded flows of two immiscible incompressible fluids with large density ratios. First, we develop an algorithm for imposing the dynamic contact Angle Boundary conditions to the Cahn–Hilliard equation. Our algorithm consists of two components: (i) we ignore the Boundary conditions and transform the Cahn–Hilliard equation into two nominally de-coupled Helmholtz type equations; (ii) we treat the dynamic contact Angle Boundary conditions in such a manner that the two Helmholtz-type equations are truly de-coupled. Then, we combine this algorithm, together with a scheme for variable-density Navier–Stokes equations we developed recently, to form an efficient method for the coupled system of Navier–Stokes and Cahn–Hilliard equations for contact line problems involving large density ratios. The overall method can deal with moving contact lines under dynamic and also static contact Angle Boundary conditions. It is endowed with several attractive features that make the method very efficient. In particular, computations for all flow variables are completely decoupled. The resultant linear algebraic systems after discretization for all flow variables involve only constant and time-independent coefficient matrices, which can be pre-computed during pre-processing, even though the coupled Navier–Stokes/Cahn–Hilliard system involves variable density and variable viscosity. Ample numerical simulations of wall-bounded air/water two-phase flows have been presented to demonstrate the capability of the method for dealing with contact line problems under dynamic and static contact-Angle conditions involving large density ratios.
Jean Marc Olive - One of the best experts on this subject based on the ideXlab platform.
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effects of microstructure and local mechanical fields on intergranular stress corrosion cracking of a friction stir welded aluminum copper lithium 2050 nugget
Corrosion Science, 2014Co-Authors: Matthieu Dhondt, Isabelle Aubert, Nicolas Saintier, Jean Marc OliveAbstract:Abstract The effects of the microstructure and mechanical fields on intergranular stress corrosion cracking (IGSCC) of the nugget zone of heat treated welds obtained by friction stir welding in the AA2050 aluminum alloy have been investigated at different scales. At low strain rate, in 1.0 NaCl aqueous solution, IGSCC develops in the microstructure, whereas only pitting corrosion is observed without any mechanical stress. Based on surface observations, EBSD analysis and X-ray tomography, the key role of sub-millimetric textured bands (induced by the welding process) on the IGSCC is demonstrated. Analyses at a more local scale show the grain Boundary (low Angle Boundary, special coincident site lattice Boundary or high Angle Boundary) do not have a significant effect on crack initiation. Crystal plasticity finite element calculations show that the threshold normal stress at grain boundaries for IGSCC development is about 80% of the macroscopic stress. It is also highlighted by crystal plasticity calculations that there is a drastic effect of the local stress field on the shape of cracks. Finally, it is shown that plasticity induced residual stresses are sufficient for the formation of IGSCC.
Béatrice Rivière - One of the best experts on this subject based on the ideXlab platform.
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an energy based equilibrium contact Angle Boundary condition on jagged surfaces for phase field methods
Journal of Colloid and Interface Science, 2018Co-Authors: Florian Frank, Faruk O Alpak, Alessio Scanziani, Béatrice RivièreAbstract:Abstract We consider an energy-based Boundary condition to impose an equilibrium wetting Angle for the Cahn–Hilliard–Navier–Stokes phase-field model on voxel-set-type computational domains. These domains typically stem from μ CT (micro computed tomography) imaging of porous rock and approximate a (on μ m scale) smooth domain with a certain resolution. Planar surfaces that are perpendicular to the main axes are naturally approximated by a layer of voxels. However, planar surfaces in any other directions and curved surfaces yield a jagged/topologically rough surface approximation by voxels. For the standard Cahn–Hilliard formulation, where the contact Angle between the diffuse interface and the domain Boundary (fluid–solid interface/wall) is 90 ° , jagged surfaces have no impact on the contact Angle. However, a prescribed contact Angle smaller or larger than 90 ° on jagged voxel surfaces is amplified. As a remedy, we propose the introduction of surface energy correction factors for each fluid–solid voxel face that counterbalance the difference of the voxel-set surface area with the underlying smooth one. The discretization of the model equations is performed with the discontinuous Galerkin method. However, the presented semi-analytical approach of correcting the surface energy is equally applicable to other direct numerical methods such as finite elements, finite volumes, or finite differences, since the correction factors appear in the strong formulation of the model.
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an energy based equilibrium contact Angle Boundary condition on jagged surfaces for phase field methods
arXiv: Fluid Dynamics, 2017Co-Authors: Florian Frank, Faruk O Alpak, Alessio Scanziani, Béatrice RivièreAbstract:We consider an energy-based Boundary condition to impose an equilibrium wetting Angle for the Cahn-Hilliard-Navier-Stokes phase-field model on voxel-set-type computational domains. These domains typically stem from the micro-CT imaging of porous rock and approximate a (on {\mu}m scale) smooth domain with a certain resolution. Planar surfaces that are perpendicular to the main axes are naturally approximated by a layer of voxels. However, planar surfaces in any other directions and curved surfaces yield a jagged/rough surface approximation by voxels. For the standard Cahn-Hilliard formulation, where the contact Angle between the diffuse interface and the domain Boundary (fluid-solid interface/wall) is 90 degrees, jagged surfaces have no impact on the contact Angle. However, a prescribed contact Angle smaller or larger than 90 degrees on jagged voxel surfaces is amplified in either direction. As a remedy, we propose the introduction of surface energy correction factors for each fluid-solid voxel face that counterbalance the difference of the voxel-set surface area with the underlying smooth one. The discretization of the model equations is performed with the discontinuous Galerkin method, however, the presented semi-analytical approach of correcting the surface energy is equally applicable to other direct numerical methods such as finite elements, finite volumes, or finite differences, since the correction factors appear in the strong formulation of the model.
Matthieu Dhondt - One of the best experts on this subject based on the ideXlab platform.
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effects of microstructure and local mechanical fields on intergranular stress corrosion cracking of a friction stir welded aluminum copper lithium 2050 nugget
Corrosion Science, 2014Co-Authors: Matthieu Dhondt, Isabelle Aubert, Nicolas Saintier, Jean Marc OliveAbstract:Abstract The effects of the microstructure and mechanical fields on intergranular stress corrosion cracking (IGSCC) of the nugget zone of heat treated welds obtained by friction stir welding in the AA2050 aluminum alloy have been investigated at different scales. At low strain rate, in 1.0 NaCl aqueous solution, IGSCC develops in the microstructure, whereas only pitting corrosion is observed without any mechanical stress. Based on surface observations, EBSD analysis and X-ray tomography, the key role of sub-millimetric textured bands (induced by the welding process) on the IGSCC is demonstrated. Analyses at a more local scale show the grain Boundary (low Angle Boundary, special coincident site lattice Boundary or high Angle Boundary) do not have a significant effect on crack initiation. Crystal plasticity finite element calculations show that the threshold normal stress at grain boundaries for IGSCC development is about 80% of the macroscopic stress. It is also highlighted by crystal plasticity calculations that there is a drastic effect of the local stress field on the shape of cracks. Finally, it is shown that plasticity induced residual stresses are sufficient for the formation of IGSCC.
Faruk O Alpak - One of the best experts on this subject based on the ideXlab platform.
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an energy based equilibrium contact Angle Boundary condition on jagged surfaces for phase field methods
Journal of Colloid and Interface Science, 2018Co-Authors: Florian Frank, Faruk O Alpak, Alessio Scanziani, Béatrice RivièreAbstract:Abstract We consider an energy-based Boundary condition to impose an equilibrium wetting Angle for the Cahn–Hilliard–Navier–Stokes phase-field model on voxel-set-type computational domains. These domains typically stem from μ CT (micro computed tomography) imaging of porous rock and approximate a (on μ m scale) smooth domain with a certain resolution. Planar surfaces that are perpendicular to the main axes are naturally approximated by a layer of voxels. However, planar surfaces in any other directions and curved surfaces yield a jagged/topologically rough surface approximation by voxels. For the standard Cahn–Hilliard formulation, where the contact Angle between the diffuse interface and the domain Boundary (fluid–solid interface/wall) is 90 ° , jagged surfaces have no impact on the contact Angle. However, a prescribed contact Angle smaller or larger than 90 ° on jagged voxel surfaces is amplified. As a remedy, we propose the introduction of surface energy correction factors for each fluid–solid voxel face that counterbalance the difference of the voxel-set surface area with the underlying smooth one. The discretization of the model equations is performed with the discontinuous Galerkin method. However, the presented semi-analytical approach of correcting the surface energy is equally applicable to other direct numerical methods such as finite elements, finite volumes, or finite differences, since the correction factors appear in the strong formulation of the model.
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an energy based equilibrium contact Angle Boundary condition on jagged surfaces for phase field methods
arXiv: Fluid Dynamics, 2017Co-Authors: Florian Frank, Faruk O Alpak, Alessio Scanziani, Béatrice RivièreAbstract:We consider an energy-based Boundary condition to impose an equilibrium wetting Angle for the Cahn-Hilliard-Navier-Stokes phase-field model on voxel-set-type computational domains. These domains typically stem from the micro-CT imaging of porous rock and approximate a (on {\mu}m scale) smooth domain with a certain resolution. Planar surfaces that are perpendicular to the main axes are naturally approximated by a layer of voxels. However, planar surfaces in any other directions and curved surfaces yield a jagged/rough surface approximation by voxels. For the standard Cahn-Hilliard formulation, where the contact Angle between the diffuse interface and the domain Boundary (fluid-solid interface/wall) is 90 degrees, jagged surfaces have no impact on the contact Angle. However, a prescribed contact Angle smaller or larger than 90 degrees on jagged voxel surfaces is amplified in either direction. As a remedy, we propose the introduction of surface energy correction factors for each fluid-solid voxel face that counterbalance the difference of the voxel-set surface area with the underlying smooth one. The discretization of the model equations is performed with the discontinuous Galerkin method, however, the presented semi-analytical approach of correcting the surface energy is equally applicable to other direct numerical methods such as finite elements, finite volumes, or finite differences, since the correction factors appear in the strong formulation of the model.