The damping effects on the free-surface motions due to the presence of the deformable solid bodies suspended in the fluid were numerically investigated. The computational method is based on a full Eulerian model that can deal with the interactions between Newtonian fluids and visco-hyperelastic solid bodies. In the numerical predictions, the free-surface motions caused by the so-called dam-break conditions, including four spherical visco-hyperelastic bodies, were calculated with two cases of non-dimensional shear moduli, G = 0.1 and 10.0, of the visco-hyperelastic bodies, which have the same density as that of the liquid phase. As a result of the computations, the following reasonable results were obtained; when the solid bodies are highly flexible (G = 0.1), the free-surface motions are almost the same as those having no solid bodies. In contrast, it was demonstrated that the damping effects are obviously large in case that the stiffness of solid bodies increases (G = 10.0).
This study deals with the applicability of the multiphase computational method (MICS), which enables us to calculate incompressible and immiscible gas-liquid phases including rigid solid bodies modeled by the discrete element method (DEM). To confirm the validity of the computational method, it is applied to the dam-break flows including multiple particles through a porous media structure consisting of circular objects fixed in the space. The structure is modeled by arranging particles in a line with a constant gap between the adjacent objects. It is shown that the calculated results of fluid flows without particles are in good agreement with experimental results. In addition, it is demonstrated that the movable particles in the flows are trapped by the porous structure and that the behaviors of fluids and transported particles are reasonably calculated in the cases of inviscid and viscous liquids in the computations.
Beam physics issue was investigated using a Malmberg-Penning trap device as a small experimental apparatus with electrons, which can be regarded as equivalent to the charged particle beam. In this study, we investigated numerically the particle dynamics in comparison with the experiment result from the view point of softening parameter adjusting. It is considered that the process of the fast electron generation was caused by multi-particle collisions.
In this research, we simulated the plasmonic properties of a single metal nanodisk excited by an optical vortex beam (OVB) using the discrete dipole approximation (DDA) method. The properties of the extinction spectra are related to the diameter and thickness of the gold nanodisk, and these spectra showed a sharper peak at shorter wavelength ranges compared to using linear polarized Gaussian beams. The peak wavelength shifts depending on the structural parameter when excited by a Gaussian beam. However, in the case of OVB use, there is minimal change observed in the peak wavelength. This tendency indicates that the localized plasmon resonance (LPR) properties excited by an OVB are dominated by the state of the excitation beam and not the shape and size of nanostructures. Focusing on distributions of photoelectric fields at peak wavelengths, the excited hexapole type mode showed behaviors of the resonance while rotating over time. This phenomenon is not seen in general excitation. These plasmonic properties reflect the temporal and spatial phase change of incident OVBs are of great interest. These results indicate that LPR properties can be designed by tuning not only the material, shape, and size, but also the condition of light excitation.
Many people would benefit from an intelligent wheelchair that is a power wheelchair to which sensors, computers, and assistive technologies are attached. However, the sufficient performance of intelligent wheelchairs cannot be obtained at indoor crossroad due to the blind spot of the sensors. In this paper, to improve the safety in environment like that, we develop a leading robot to guide safely power wheelchairs.
The leading robot is equipped with several sensors and precedes power wheelchairs. Then, the leading robot guides power wheelchairs while checking the safety of the surroundings. The leading robot detects the obstacle ahead of the power wheelchairs by the sensor on the leading robot, and the power wheelchairs can safely avoid the obstacle. In addition, blind spots of sensors can be reduced, since the leading robot is free to mount sensors. Therefore, the system can ensure sufficient safety.
In this paper, we realize the motion algorithm of a leading robot by the virtual potential field method to avoid dynamic obstacles such as pedestrians at indoor environment. Then, we execute the motion simulation of the leading robot system at an indoor crossroad, and we confirm the effectiveness of the system.