Effect of liquid volume fraction and shear rate on rheological properties and microstructure formation in ternary particle/oil/water dispersion systems under shear flow: two-dimensional direct numerical simulation.

We numerically studied the rheological properties and microstructure formation under shear flow in a ternary particle/oil/water dispersion system. Our numerical simulation method was based on a phase-field model for capturing a free interface, the discrete element method for tracking particle motion, the immersed boundary method for calculating fluid-particle interactions, and a wetting model that assigns an order parameter to the solid surface according to the wettability. The effects of the water-phase volume fraction and shear rate on the microstructure and apparent viscosity were investigated.

Lattice Boltzmann model for capillary interactions between particles at a liquid-vapor interface under gravity.

A computational technique based on the lattice Boltzmann method (LBM) is developed to simulate the wettable particles adsorbed to a liquid-vapor interface under gravity. The proposed technique combines the improved smoothed-profile LBM for the treatment of moving solid particles in a fluid and the free-energy LBM for the description of a liquid-vapor system. Five benchmark two-dimensional problems are examined: (A) a stationary liquid drop in the vapor phase; a wettable particle adsorbed to a liquid-vapor interface in (B) the absence and (C) the presence of gravity; (D) two freely moving particles at a liquid-vapor interface in the presence of gravity (i.

High-Resolution Numerical Simulation of Microfiltration of Oil-in-Water Emulsion Permeating through a Realistic Membrane Microporous Structure Generated by Focused Ion Beam Scanning Electron Microscopy Images.

Owing to the limitations of visualization techniques in experimental studies and low-resolution numerical models based on computational fluid dynamics (CFD), the detailed behavior of oil droplets during microfiltration is not well understood. Hence, a high-resolution CFD model based on an in-house direct numerical simulation (DNS) code was constructed in this study to analyze the detailed dynamics of an oil-in-water (O/W) emulsion using a microfiltration membrane. The realistic microporous structure of commercial ceramic microfiltration membranes (mullite and α-alumina membranes) was obtained using an image processing technique based on focused ion beam scanning electron microscopy (FIB-SEM).

Simulation on Pore Formation from Polymer Solution at Surface in Contact with Solid Substrate via Thermally Induced Phase Separation.

The formation of porous structures from polymer solutions at the surface in contact with various solid surfaces via a thermally-induced phase separation (TIPS) process is investigated. The pore formation process at the bulk and the surface of the poly(methyl methacrylate)/cyclohexanol solution is simulated with a model based on the phase field method. When the compatibilities between the polymer-rich phase formed by the phase separation and the solid surface are high or low, surface porosity decreases.

Lattice Boltzmann method for simulation of wettable particles at a fluid-fluid interface under gravity.

A computational technique was developed to simulate wettable particles trapped at a fluid-fluid interface under gravity. The proposed technique combines the improved smoothed profile-lattice Boltzmann method (iSP-LBM) for the treatment of moving solid-fluid boundaries and the free-energy LBM for the description of isodensity immiscible two-phase flows. We considered five benchmark problems in two-dimensional systems, including a stationary drop, a wettable particle trapped at a fluid-fluid interface in the absence or presence of gravity, two freely moving particles at a fluid-fluid interface in the presence of gravity (i.

Effect of internal mass in the lattice Boltzmann simulation of moving solid bodies by the smoothed-profile method.

A computational method for the simulation of particulate flows that can efficiently treat the particle-fluid boundary in systems containing many particles was developed based on the smoothed-profile lattice Boltzmann method (SPLBM). In our proposed method, which we call the improved SPLBM (iSPLBM), for an accurate and stable simulation of particulate flows, the hydrodynamic force on a moving solid particle is exactly formulated with consideration of the effect of internal fluid mass. To validate the accuracy and stability of iSPLBM, we conducted numerical simulations of several particulate flow systems and compared our results with those of other simulations and some experiments.

In situ observation of meniscus shape deformation with colloidal stripe pattern formation in convective self-assembly.

Vertical convective self-assembly is capable of fabricating stripe-patterned structures of colloidal particles with well-ordered periodicity. To unveil the mechanism of the stripe pattern formation, in the present study, we focus on the meniscus shape and conduct in situ observations of shape deformation associated with particulate line evolution. The results reveal that the meniscus is elongated downward in a concave fashion toward the substrate in accordance with solvent evaporation, while the concave deformation is accelerated by solvent flow, resulting in the rupture of the liquid film at the thinnest point of the meniscus.

Permeation of concentrated oil-in-water emulsions through a membrane pore: numerical simulation using a coupled level set and the volume-of-fluid method.

In this paper, we investigated the demulsification behavior of oil-in-water (O/W) emulsions during membrane permeation in the oil-water separation process using a numerical simulation approach. To accurately deal with the large deformation of the oil-water interface by coalescence and wetting, and to estimate the volume of the coalesced oil droplet, the coupled level set and volume-of-fluid method was used as the interface capturing method. We applied the simulation model to the permeation of O/W emulsions through a membrane pore, and then investigated the effects of the wettability of the membrane surface, filtration flux, and pore size on the demulsification efficiency.

Formation of regular stripes of chemically converted graphene on hydrophilic substrates.

Chemically converted graphene (CCG), from a chemistry point of view, is a giant molecule with a unique two-dimensional (2D) configuration. The availability of CCG dispersion provides a range of scalable methods to assemble graphene-based materials but brings the challenge of understanding and control of the CCG morphology in solution processing. In this study, we found that, similar to conventional colloidal systems (e.

Spontaneous formation of cluster array of gold particles by convective self-assembly.

Cluster arrays composed of metal nanoparticles are promising for application in sensing devices because of their interesting surface plasmon characteristics. Herein, we report the spontaneous formation of cluster arrays of gold colloids on flat substrates by vertical-deposition convective self-assembly. In this technique, under controlled temperature, a hydrophilic substrate is vertically immersed in a colloid suspension.

Colloidal stripe pattern with controlled periodicity by convective self-assembly with liquid-level manipulation.

We describe a template-free technique for arranging colloidal particles into a stripe pattern on a large scale. A simple liquid-level manipulation system was incorporated into the vertical-deposition convective self-assembly (CSA) technique. By periodically pumping a colloidal dispersion out of or into a reservoir to manipulate the liquid level, we successfully fabricated stripe patterns with various periodicities (i.

Fabrication of colloidal grid network by two-step convective self-assembly.

We explored a "template-free" approach to arranging colloidal particles into a network pattern by a convective self-assembly technique. In this approach, which we call "two-step convective self-assembly," a stripe pattern of colloidal particles is first prepared on a substrate by immersing it in a suspension. The substrate with the stripes is then rotated by 90° and again immersed in the suspension to produce stripes perpendicular to the first ones, resulting in a grid-pattern network of colloidal arrays.

Calculating the gravitational self-force in Schwarzschild spacetime.

We present a practical method for calculating the local gravitational self-force (often called "radiation-reaction force") for a pointlike particle orbiting a Schwarzschild black hole. This is an implementation of the method of mode-sum regularization, in which one first calculates the (finite) contribution to the force due to each individual multipole mode of the perturbation, and then applies a certain regularization procedure to the mode sum. Here we give the values of all the "regularization parameters" required for implementing this regularization procedure, for any geodesic orbit in Schwarzschild spacetime.