Naoki Takada | National Institute of Advanced Industrial Science and Technology (original) (raw)
Papers by Naoki Takada
Transport in Porous Media, 2018
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The Proceedings of Conference of Kansai Branch, 2001
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The Proceedings of The Computational Mechanics Conference, 2000
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The Proceedings of The Computational Mechanics Conference, 2016
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Journal of Computational Multiphase Flows, 2014
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Mathematics and Computers in Simulation, 2006
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2007 Proceedings of the 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, 2007
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JAPANESE JOURNAL OF MULTIPHASE FLOW, 2014
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The effects of the diameter ratio λ (= d / D, where d and D are the diameters of a drop and a pip... more The effects of the diameter ratio λ (= d / D, where d and D are the diameters of a drop and a pipe, respectively), the Morton number M and the viscosity ratio κ (= µ d / µ c , where µ is the viscosity and the subscripts d and c are the dispersed fluid particle and the continuous phase, respectively) on terminal velocities and shapes of single drops rising through stagnant liquids in a vertical pipe are investigated experimentally. Then, the drops in the pipe are simulated using a volume tracking method with various coordinate systems, i.e., three-dimensional (3D) cylindrical coordinates, 3D general curvilinear coordinates and 3D Cartesian coordinates. Predicted velocities and shapes of the drops using three coordinate systems are compared with the measured data to examine the effects of coordinate systems on the accuracy of prediction. As a result, (1) The velocity ratio V T / V T0 (V T and V T0 are the terminal velocity in a pipe and infinite liquid, respectively) decreases as λ in...
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In this study, a phase-field method adopting Navier-Stokes equations, NS-PFM, is applied to fluid... more In this study, a phase-field method adopting Navier-Stokes equations, NS-PFM, is applied to fluid dynamic problems for examining the fundamental capability to simulate motions of incompressible isothermal two-phase fluid in various micro devices. The interfacial modeling is based on the van der Waals-Cahn-Hilliard free-energy theory. Wettability of solid surface is taken into account through a simple boundary condition derived from free-energy increase per unit area on the surface. The numerical simulations are carried out at a high density ratio equivalent to that of air-water system under no gravity. Major findings are as follows: (1) Static contact angle of liquid drop on solid surface is flexibly controlled by a parameter of wetting potential in the boundary condition. (2) Interfacial motion of two-phase fluid in a rectilinear channel is accelerated locally on a hydrophilic region of the solid surface. (3) NS-PFM successfully captures displacement and breakup motions of single l...
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Polymers
We investigated the enhancement of the capillary effect in a plastic capillary tube using only a ... more We investigated the enhancement of the capillary effect in a plastic capillary tube using only a nanostructured surface. Since plastic is a hydrophobic material, the capillary effect does not emerge without an additional coating or plasma treatment process. Therefore, capillary effect enhancement by the nanostructure fabrication method is expected to reduce the cost and minimise the contamination produced in the human body. By combining a hydrophilic nylon resin and a nanostructure at the tip of the plastic pipette, we could confirm that the capillary effect was produced solely by the tube fabrication process. The produced capillary effect increased linearly with increasing nanostructure height when a standard solution with a surface tension of 70 mN·m−1 was used. Thus, we can conclude that including the plastic part with nanostructure can be useful for biomedical applications. In addition, we suggest that the proposed method is highly effective in controlling the wetting properties...
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For interface-tracking simulation of incompressible two-phase fluids with high density ratios, a ... more For interface-tracking simulation of incompressible two-phase fluids with high density ratios, a new numerical method was proposed by combining Navier-Stokes equations with a phase-field model based on a van der Waals-Cahn-Hilliard free-energy theory. The method was applied to several benchmark problems. Major findings are as follows: (1) The volume flux derived from a local chemical potential gradient in the Cahn-Hilliard equation leads to accurate volume conservation, autonomic reconstruction of gas-liquid interface, and reduction of numerical diffusion and oscillation. (2) The proposed method gave good predictions of pressure increase inside a bubble caused by the surface tension force. (3) A single liquid drop falling in stagnant gas and merging into a stagnant liquid film was successfully simulated.
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The purpose of this study is to examine multi-physics computational fluid dynamics method, NS-PFM... more The purpose of this study is to examine multi-physics computational fluid dynamics method, NS-PFM, which is a combination of Navier-Stokes (NS) equations with phase-field model (PFM) based on the free-energy theory, for interfacecapturing/tracking simulation of two-phase flows. First, a new NS-PFM which we have proposed was applied to immiscible, incompressible, isothermal two-phase flow problems with a high density ratio equivalent to that of an air-water system. In this method, a Cahn-Hilliard equation was used for prediction of diffusive interface configuration. The numerical simulations demonstrated that (1) predicted collapse of two-dimensional liquid column in a gas under gravity agreed well with available data at aspect ratios of column = 1 and 2, and (2) coalescence of free-fall drops into a liquid film was successfully simulated in three dimensions. Second, we took heat transfer into account in another NS-PFM which solves a full set of NS equations and the van-der-Waals equ...
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Our objective in this study is to examine the applicability of a computational fluid dynamics (CF... more Our objective in this study is to examine the applicability of a computational fluid dynamics (CFD) method to simulation of motions of microscopic two-phase fluid on solid surfaces with edges for evaluating fluidic devices and for predicting underground fluid flows through porous media. The method adopts the phase-field model (PFM) for fluid-fluid interfacial dynamics and the lattice-Boltzmann method (LBM) as numerical scheme for solving a set of two-phase fluid-dynamics equations. Based on the free-energy theory, the PFM reproduces an interface as a finite volumetric zone between phases without imposing topological constraints on interface as phase boundary. Wettability of solid surface to fluid is taken into account through minimizing the free energy of the fluid plus the surface energy per unit area. The LBM assumes that a macroscopic fluid consists of fictitious mesoscopic particles repeating collisions with each other and rectilinear translations with an isotropic discrete velo...
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We investigated the enhancement of the capillary effect in a plastic capillary tube using only a ... more We investigated the enhancement of the capillary effect in a plastic capillary tube using only a nanostructured surface. Since plastic is a hydrophobic material, the capillary effect does not emerge without an additional coating or plasma treatment process. Therefore, capillary effect enhancement by the nanostructure fabrication method is expected to reduce the cost and minimise the contamination produced in the human body. By combining a hydrophilic nylon resin and a nanostructure at the tip of the plastic pipette, we could confirm that the capillary effect was produced solely by the tube fabrication process. The produced capillary effect increased linearly with increasing nanostructure height when a standard solution with a surface tension of 70 mN·m−1 was used. Thus, we can conclude that including the plastic part with nanostructure can be useful for biomedical applications. In addition, we suggest that the proposed method is highly effective in controlling the wetting properties...
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Allen-Cahn (AC) and Cahn-Hilliard (CH)-type diffuse-interface advection equations based on a phas... more Allen-Cahn (AC) and Cahn-Hilliard (CH)-type diffuse-interface advection equations based on a phase-field model (PFM) are evaluated for computational fluid dynamics (CFD) simulation of motions of microscopic immiscible incompressible isothermal two-phase fluid contacting solid surface. For solving a conservation-modified AC equation, a lattice-Boltzmann method (LBM) based on fictitious mesocsopic particle kinematics is adopted. The modified AC and CH equations without interfacial curvature-induced diffusion flux are tested through a benchmark problem of interfacial advection. It is confirmed that both the volume and the shape of fluid with diffusive interface are well conserved during the advection. In addition, for developing a novel micro-fabrication process of flexible and largearea sheet display device, immiscible liquid-liquid two-phase slug droplets formation in Tjunction microchannel with square cross section and hydrophilic solid walls is investigated through CFD simulation u...
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The Proceedings of Conference of Kansai Branch
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Computers & Fluids
Abstract The phase-field (PF) method is a method for interface tracking that can treat complex to... more Abstract The phase-field (PF) method is a method for interface tracking that can treat complex topological changes relatively easily because of its diffuse interface model. Therefore, as computational resources become increasingly powerful, it is a promising interface tracking method for multiphase flow problems. In this study, we developed a novel multi-PF (MPF) model for expressing flows that consist of an arbitrary number of phases. Here, we adopt the conservative Allen–Cahn (CAC) model instead of the Cahn–Hilliard model, which is often employed in multiphase flow problems, to reduce computational cost and increase the flexibility of the model for various problems. Six sets of two-dimensional simulations were performed to confirm the validity of the developed model for simulating the static and dynamic phenomena of the multiphase flow problem while conserving the volume of each phase. The results confirm that the developed CAC-type MPF model can accurately express the contact angle of a droplet placed on a solid substrate and the motion of bubbles interacting with liquid–liquid interfaces.
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For simulating immiscible two-phase flows and realizing the easy adjustment of surface tension an... more For simulating immiscible two-phase flows and realizing the easy adjustment of surface tension and interface thickness to desired values, a lattice-Boltzmann binary fluid model is improved by (a) the adoption of a particle number density function at a local equilibrium state for the convection term of the lattice Boltzmann equation and (b) the introduction of two parameters in a surface free energy. Neutrally-buoyant drops in simple shear flows are simulated using the improved method to examine its accuracy and characteristics of drop breakup. As a result, it is confirmed that (1) the method can give good predictions for deformation and breakup of single drops and (2) the critical Reynolds number at which drop breakup takes place depends not only on the capillary number and the number density of drops but also on the initial spatial arrangement of drops.
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The Proceedings of The Computational Mechanics Conference
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Transport in Porous Media, 2018
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The Proceedings of Conference of Kansai Branch, 2001
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The Proceedings of The Computational Mechanics Conference, 2000
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The Proceedings of The Computational Mechanics Conference, 2016
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Journal of Computational Multiphase Flows, 2014
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Mathematics and Computers in Simulation, 2006
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2007 Proceedings of the 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, 2007
Bookmarks Related papers MentionsView impact
JAPANESE JOURNAL OF MULTIPHASE FLOW, 2014
Bookmarks Related papers MentionsView impact
The effects of the diameter ratio λ (= d / D, where d and D are the diameters of a drop and a pip... more The effects of the diameter ratio λ (= d / D, where d and D are the diameters of a drop and a pipe, respectively), the Morton number M and the viscosity ratio κ (= µ d / µ c , where µ is the viscosity and the subscripts d and c are the dispersed fluid particle and the continuous phase, respectively) on terminal velocities and shapes of single drops rising through stagnant liquids in a vertical pipe are investigated experimentally. Then, the drops in the pipe are simulated using a volume tracking method with various coordinate systems, i.e., three-dimensional (3D) cylindrical coordinates, 3D general curvilinear coordinates and 3D Cartesian coordinates. Predicted velocities and shapes of the drops using three coordinate systems are compared with the measured data to examine the effects of coordinate systems on the accuracy of prediction. As a result, (1) The velocity ratio V T / V T0 (V T and V T0 are the terminal velocity in a pipe and infinite liquid, respectively) decreases as λ in...
Bookmarks Related papers MentionsView impact
In this study, a phase-field method adopting Navier-Stokes equations, NS-PFM, is applied to fluid... more In this study, a phase-field method adopting Navier-Stokes equations, NS-PFM, is applied to fluid dynamic problems for examining the fundamental capability to simulate motions of incompressible isothermal two-phase fluid in various micro devices. The interfacial modeling is based on the van der Waals-Cahn-Hilliard free-energy theory. Wettability of solid surface is taken into account through a simple boundary condition derived from free-energy increase per unit area on the surface. The numerical simulations are carried out at a high density ratio equivalent to that of air-water system under no gravity. Major findings are as follows: (1) Static contact angle of liquid drop on solid surface is flexibly controlled by a parameter of wetting potential in the boundary condition. (2) Interfacial motion of two-phase fluid in a rectilinear channel is accelerated locally on a hydrophilic region of the solid surface. (3) NS-PFM successfully captures displacement and breakup motions of single l...
Bookmarks Related papers MentionsView impact
Polymers
We investigated the enhancement of the capillary effect in a plastic capillary tube using only a ... more We investigated the enhancement of the capillary effect in a plastic capillary tube using only a nanostructured surface. Since plastic is a hydrophobic material, the capillary effect does not emerge without an additional coating or plasma treatment process. Therefore, capillary effect enhancement by the nanostructure fabrication method is expected to reduce the cost and minimise the contamination produced in the human body. By combining a hydrophilic nylon resin and a nanostructure at the tip of the plastic pipette, we could confirm that the capillary effect was produced solely by the tube fabrication process. The produced capillary effect increased linearly with increasing nanostructure height when a standard solution with a surface tension of 70 mN·m−1 was used. Thus, we can conclude that including the plastic part with nanostructure can be useful for biomedical applications. In addition, we suggest that the proposed method is highly effective in controlling the wetting properties...
Bookmarks Related papers MentionsView impact
For interface-tracking simulation of incompressible two-phase fluids with high density ratios, a ... more For interface-tracking simulation of incompressible two-phase fluids with high density ratios, a new numerical method was proposed by combining Navier-Stokes equations with a phase-field model based on a van der Waals-Cahn-Hilliard free-energy theory. The method was applied to several benchmark problems. Major findings are as follows: (1) The volume flux derived from a local chemical potential gradient in the Cahn-Hilliard equation leads to accurate volume conservation, autonomic reconstruction of gas-liquid interface, and reduction of numerical diffusion and oscillation. (2) The proposed method gave good predictions of pressure increase inside a bubble caused by the surface tension force. (3) A single liquid drop falling in stagnant gas and merging into a stagnant liquid film was successfully simulated.
Bookmarks Related papers MentionsView impact
The purpose of this study is to examine multi-physics computational fluid dynamics method, NS-PFM... more The purpose of this study is to examine multi-physics computational fluid dynamics method, NS-PFM, which is a combination of Navier-Stokes (NS) equations with phase-field model (PFM) based on the free-energy theory, for interfacecapturing/tracking simulation of two-phase flows. First, a new NS-PFM which we have proposed was applied to immiscible, incompressible, isothermal two-phase flow problems with a high density ratio equivalent to that of an air-water system. In this method, a Cahn-Hilliard equation was used for prediction of diffusive interface configuration. The numerical simulations demonstrated that (1) predicted collapse of two-dimensional liquid column in a gas under gravity agreed well with available data at aspect ratios of column = 1 and 2, and (2) coalescence of free-fall drops into a liquid film was successfully simulated in three dimensions. Second, we took heat transfer into account in another NS-PFM which solves a full set of NS equations and the van-der-Waals equ...
Bookmarks Related papers MentionsView impact
Our objective in this study is to examine the applicability of a computational fluid dynamics (CF... more Our objective in this study is to examine the applicability of a computational fluid dynamics (CFD) method to simulation of motions of microscopic two-phase fluid on solid surfaces with edges for evaluating fluidic devices and for predicting underground fluid flows through porous media. The method adopts the phase-field model (PFM) for fluid-fluid interfacial dynamics and the lattice-Boltzmann method (LBM) as numerical scheme for solving a set of two-phase fluid-dynamics equations. Based on the free-energy theory, the PFM reproduces an interface as a finite volumetric zone between phases without imposing topological constraints on interface as phase boundary. Wettability of solid surface to fluid is taken into account through minimizing the free energy of the fluid plus the surface energy per unit area. The LBM assumes that a macroscopic fluid consists of fictitious mesoscopic particles repeating collisions with each other and rectilinear translations with an isotropic discrete velo...
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We investigated the enhancement of the capillary effect in a plastic capillary tube using only a ... more We investigated the enhancement of the capillary effect in a plastic capillary tube using only a nanostructured surface. Since plastic is a hydrophobic material, the capillary effect does not emerge without an additional coating or plasma treatment process. Therefore, capillary effect enhancement by the nanostructure fabrication method is expected to reduce the cost and minimise the contamination produced in the human body. By combining a hydrophilic nylon resin and a nanostructure at the tip of the plastic pipette, we could confirm that the capillary effect was produced solely by the tube fabrication process. The produced capillary effect increased linearly with increasing nanostructure height when a standard solution with a surface tension of 70 mN·m−1 was used. Thus, we can conclude that including the plastic part with nanostructure can be useful for biomedical applications. In addition, we suggest that the proposed method is highly effective in controlling the wetting properties...
Bookmarks Related papers MentionsView impact
Allen-Cahn (AC) and Cahn-Hilliard (CH)-type diffuse-interface advection equations based on a phas... more Allen-Cahn (AC) and Cahn-Hilliard (CH)-type diffuse-interface advection equations based on a phase-field model (PFM) are evaluated for computational fluid dynamics (CFD) simulation of motions of microscopic immiscible incompressible isothermal two-phase fluid contacting solid surface. For solving a conservation-modified AC equation, a lattice-Boltzmann method (LBM) based on fictitious mesocsopic particle kinematics is adopted. The modified AC and CH equations without interfacial curvature-induced diffusion flux are tested through a benchmark problem of interfacial advection. It is confirmed that both the volume and the shape of fluid with diffusive interface are well conserved during the advection. In addition, for developing a novel micro-fabrication process of flexible and largearea sheet display device, immiscible liquid-liquid two-phase slug droplets formation in Tjunction microchannel with square cross section and hydrophilic solid walls is investigated through CFD simulation u...
Bookmarks Related papers MentionsView impact
The Proceedings of Conference of Kansai Branch
Bookmarks Related papers MentionsView impact
Computers & Fluids
Abstract The phase-field (PF) method is a method for interface tracking that can treat complex to... more Abstract The phase-field (PF) method is a method for interface tracking that can treat complex topological changes relatively easily because of its diffuse interface model. Therefore, as computational resources become increasingly powerful, it is a promising interface tracking method for multiphase flow problems. In this study, we developed a novel multi-PF (MPF) model for expressing flows that consist of an arbitrary number of phases. Here, we adopt the conservative Allen–Cahn (CAC) model instead of the Cahn–Hilliard model, which is often employed in multiphase flow problems, to reduce computational cost and increase the flexibility of the model for various problems. Six sets of two-dimensional simulations were performed to confirm the validity of the developed model for simulating the static and dynamic phenomena of the multiphase flow problem while conserving the volume of each phase. The results confirm that the developed CAC-type MPF model can accurately express the contact angle of a droplet placed on a solid substrate and the motion of bubbles interacting with liquid–liquid interfaces.
Bookmarks Related papers MentionsView impact
For simulating immiscible two-phase flows and realizing the easy adjustment of surface tension an... more For simulating immiscible two-phase flows and realizing the easy adjustment of surface tension and interface thickness to desired values, a lattice-Boltzmann binary fluid model is improved by (a) the adoption of a particle number density function at a local equilibrium state for the convection term of the lattice Boltzmann equation and (b) the introduction of two parameters in a surface free energy. Neutrally-buoyant drops in simple shear flows are simulated using the improved method to examine its accuracy and characteristics of drop breakup. As a result, it is confirmed that (1) the method can give good predictions for deformation and breakup of single drops and (2) the critical Reynolds number at which drop breakup takes place depends not only on the capillary number and the number density of drops but also on the initial spatial arrangement of drops.
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The Proceedings of The Computational Mechanics Conference
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