ALE finite element method for gas–liquid two-phase flow including moving boundary based on an incompressible two-fluid model

This paper proposes an ALE (Arbitrary Lagrangian–Eulerian) finite element method for gas–liquid two-phase flow, based on an incompressible two-fluid model, to analyze the two-phase flow including moving boundaries. The basic equations are derived by describing the two-fluid model in the ALE form. The solution algorithm is parallel to a fractional step method, and the Galerkin method is employed for the formulation. A quadrilateral element with four nodes is used for the discretization of the computational domain. The present method is also applied to calculate the flow around a circular cylinder, which is forced to oscillate in a quiescent air–water two-phase mixture. The drag coefficients of the cylinder exhibit periodical change in accordance with the variation of the flow around the cylinder. The time variations of the flow field and drag coefficients are discussed in relation to the oscillation of the cylinder.     

128×128 three-dimensional MEMS optical switch module with simultaneous optical path connection for optical cross-connect systems

A 128×128 three-dimensional MEMS optical switch module and a switching-control algorithm for high-speed connection and optical power stabilization are described. A prototype switch module enables the simultaneous switching of all optical paths. The insertion loss is less than 4.6 dB and is 2.3 dB on average. The switching time is less than 38 ms and is 8 ms on average. We confirmed that the maximum optical power can be obtained and optical power stabilization control is possible. The results confirm that the module is suitable for practical use in optical cross-connect systems.     

Fluoropolymer Nanosheet as a Wrapping Mount for High‐Quality Tissue Imaging

In the field of biological microscopy technology, it is still a practical challenge to obtain high‐quality tissue images, due to the tissue desiccation that occurs during observations without an effective sample mounting. Inspired by the use of plastic food wrap, this study proposes the use of polymer thin films (also known as nanosheets) to fix the tissue samples. Water‐repellent nanosheets composed of the amorphous fluoropolymer CYTOP are prepared with adjustable thicknesses and their hydrophobicity, transparency, and adhesion strength are evaluated. They show excellent water‐retention effect and work well for sample fixation. By wrapping cleared mouse brain slices with a 133 nm thick CYTOP nanosheet, this study achieves high spatial resolution neuron images while scanning over a large area for a long period of time. No visible artifacts arising from sample shrinkage can be detected. This study also expects that nanosheet wrapping could be effective over a longer time span by combination with conventional agarose embedding.     

An experimental validation of the guideline for inelastic design analysis through structural model tests

In this paper, the inelastic analysis procedures recommended to use in the advanced elevated temperature structural design guide under development in Japan for the improved design of future fast breeder reactors were validated through the structural model tests and the evaluation of the experimental results by the inelastic analyses. First, a thermal fatigue test of a 316FR hollow cylinder with two longitudinal weldments was conducted under the condition of combined constant axial load and cyclic movement of axial temperature distribution, which simulated the loading condition near the free surface of coolant sodium in the main vessel of fast breeder reactors (FBRs). In the experiments, longitudinal and radial ratcheting deformation were measured and crack initiation life was also examined. Second, the inelastic analyses were carried out in accordance with the recommended procedure by using the measured results of oscillating temperature distribution. Finally, the results of inelastic analyses were compared with the experimental results and it was validated that the recommended practice gave a conservative result for the deformation and a good estimation of strain range for the fatigue life evaluation.     

Numerical simulation for diffusion of matter in compound round jet by three-dimensional particle method

A three-dimensional particle method for the diffusion of matter in a round jet is proposed. The flow field is calculated with a vortex method, whereas the concentration field is simulated through a method analogous to the vortex method. The particle method is based on the Lagrangian approach; thus no computational grids are needed. It is applied to simulate the diffusion of matter in a compound round jet. The large-scale eddies, appearing just downstream of the disappearing point of the potential core, cause the diffusion of matter in the radial direction. In the subsequent developed region of the velocity field, the diffusion proceeds to the smaller vortical structure. The mean concentration and the concentration fluctuation intensity are in the self-preservation state at x/D?8 and x/D?13, respectively. These numerical results are favorably compared with experimental ones, indicating that the present particle method is usefully employed to simulate the diffusion of matter in a round jet.     

Modeling of soot particles growth in fuel-rich premixed flame

The soot formation process and the structure of a fuel-rich premixed flame stabilized in the downstream side of a porous medium have been investigated by experimental measurements and numerical analysis. In the numerical analysis, a modified Tesner's model for the reaction rate of soot formation has been introduced through a comparison between measured and calculated distributions of the temperature and the species mole fractions. Furthermore, a novel model for soot growth is developed, taking both surface and coalescence growths into account. On the basis of this model, the following results are obtained. Surface growth becomes dominant immediately after the beginning of soot formation. In the downstream side, the soot particle increases due to grow by the coalescence with smaller soot particles, and decrease as a result of collision with radicals and coalescence with larger soot particles.     

Numerical simulation of reacting plane mixing layer by particle method

This paper proposes a two-dimensional particle method for a plane mixing layer with a single-step and irreversible chemical reaction. The vorticity and concentration fields are discretized into the vortex and concentration elements, respectively, and the behavior of the elements is calculated with the Lagrangian method. The reaction is estimated through the calculation for the time rate of change in the strength for concentration element. The method is applied to simulate the reactive plane mixing layer. The simulation demonstrates that the mixing and reaction phenomena caused by the large-scale eddies are successfully captured. It is also confirmed that the effects of the Damköhler number and stoichiometric ratio on the reaction are favorably analyzed by the method.     

Numerical Simulation of Water Flow through Nano-Hydraulic Turbine Driven by Rapid and Shallow Stream

This study is concerned with the numerical simulation of the flow through an open type cross-flow runner of a nano-hydraulic turbine driven by rapid and shallow stream. It employs the two-dimensional particle method, which was used for the flow simulation of a small-scale hydraulic turbine of impulse-type in the prior study. The tip speed ratio 2, defined as the ratio of the runner tip speed to the water stream velocity upstream of the runner, ranges from 0.1 to 0.8. The simulated flow at 2 = 0.5 is confirmed to agree well with the experimentally visualized one. The effect of 2 on the flows inside the rotating cascade as well as around the runner is clarified. The turbine performance, calculated by using the simulated flow, is also highlighted to agree almost with the measurement. These demonstrate that the present simulation method is indeed applicable to the development of open type cross-flow runner of nano-hydraulic turbine utilizing rapid and shallow stream.     

An optical flow injection analysis system for measurement of glucose in tomato

An optical flow injection analysis (FIA) system for glucose measurement in tomato was constructed by using a glucose oxidase (GOD) immobilized reactor and a photodiode sensor, a peristaltic pump and a personal computer. The GOD reactor was crammed with strip-shaped of a GOD immobilized membrane to an acrylic pipe. The GOD was immobilized on polytetrafluoroethylene membrane by crosslinking with glutaraldehyde. Hydrogen peroxide generated by the GOD reaction oxidized luminol to produce chemiluminescence in the presence of horseradish peroxide. The chemiluminescence was detected by using the photodiode. The glucose measurement system was calibrated with standard glucose solutions. The calibration range of the system for glucose was 2.0–100.0 mmol L⁻¹. Measurement time for every sample was within 3 min. Glucose concentrations of a fresh and processed tomato samples measured with this glucose measurement system could be evaluated rapidly and non-laboriously.