The author of this paper has been developing a high-efficient hydrogen energy system which uses slush hydrogen as a means of transporting and storing hydrogen energy, and a refrigerant for cooling superconducting power machines. In this system, a synergetic or hybrid effect is anticipated for slush hydrogen transported in a pipeline and stored as a fuel for fuel cells, with simultaneous transmission and storage of electrical power by means of superconducting power machines using MgB₂ material. In this paper, thermo-fluid phenomena of cryogenic multiphase fluid in the development of this system are reported, which consist of hydrogen liquefaction by magnetic refrigeration, nucleate boiling heat transfer to slush hydrogen and liquid hydrogen, and pressure drop reduction and heat transfer deterioration phenomena of slush fluid due to the non-Newtonian fluid behavior.

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Past tsunami disasters showed us that tsunamis caused various types of damage to wide coastal areas, which were not only inundation but also destruction of houses, drift of vessels and cars, erosion of beach and others. To estimate and understand possible tsunami damage is essential to mitigate tsunami disasters and develop resilient areas and communities. The numerical simulation system named STOC has been developed to estimate tsunami damage to coastal areas in which there are a lot of structures. STOC consists of two fluid models of STOC-IC and STOC-ML and a floating body model of STOM-DM. STOC-IC is a three-dimensional and non-hydrostatic model to calculate the tsunami interacting with structures, and STOC-ML is a multi-layer model with the hydrostatic pressure assumption to calculate the tsunami propagating in the open sea. STOC-DM calculates motion of numerous floating bodies excited by drag, inertia and buoyancy forces, using data of water surface elevation and fluid velocity calculated by STOC-IC and STOC-ML. STOC has been validated in comparison with physical model tests. Furthermore, STOC is applied to an actual port area to estimate what the expected tsunami causes. The estimation results are indicated by a visualization tool developed to present the calculation results for general people in a way easy to understand.

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When a shock wave propagates over a dust layer composed of many small solid particles, lifted and dispersed particles form a dust cloud in the shock-induced flow. The dust cloud has a possibility of causing a propagating dust explosion in galleries of the coal mine and factories which treat flammable powder, so that the analysis and prediction of this phenomenon are very important to forestall the dangerous explosion. In this paper, two results of numerical simulations about the initial process of this phenomenon are introduced. The first result shows that a particle on a wall is lifted by the shock-induced flow, and a lift force on the particle changes with the clearance between the particle and the wall. The second result shows that many particles are lifted and dispersed in the shock-induced flow, and the upward velocities of lifted particles were given by particle-particle interactions rather than by fluid lift forces such as Saffman force and Magnus force. Furthermore, the computed dust cloud was almost same as observed in experiments.

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The grouting method newly developed in the present study is called Balloon grouting method. This method is effective as a countermeasure against liquefaction of ground beneath existing structures.

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The article describes the nature of highway traffic flow mainly composed of automotive four wheelers, and also introduces several technical issues to be solved by engineers. The one of the way of understanding the highway traffic flow is treated as continuous fluid flow, otherwise as dispersive individual vehicle movements. The short history of these two streams of traffic flow theories are reviewed, and the most basic diagrams useful in the analyses of highway traffic flow, such as time-space diagram, fundamental diagram and cumulative volume curve, are also introduced. One aspect of the classification of highways is the distinction of uninterrupted and interrupted flow facilities. The discharge flow from the stop line at one approach to a signalized intersection from the start of a displayed green traffic signal is the maximum flow for an interrupted flow highway facilities. The nature of 'traffic congestion', which is a typical phenomena occurred at a highway capacity bottleneck section, is discussed in general. The traffic flow is dealt as a two-phase flow with congested and uncongested flow regimes. The concept of 'traffic congestion' in an interrupted flow facilities are different from those in uninterrupted flow ones. As a simplification, Shock wave theory which can describe the direction and the wave speed of extension or diminution of the boundary of discontinuous different two highway traffic region, such as congested and uncongested traffic flow region, is introduced. The amount of excess traffic demand over a bottleneck capacity for recursive traffic congestion phenomena is also discussed.

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It is an increasing concern that the depletion of dissolved oxygen (DO) concentration at the bottom layer of the northern-part of Lake Biwa with 100m in maximum depth has been worsen in recent years not only due to eutrophication in water but also the effects of global warming such as the raise of air temperature during winter. Many research have been carried out by various organizations to clarify the mechanism of DO depletion near the lake bottom and to propose the countermeasures. This article firstly describes the seasonal variations of the vertical water temperature and water quality distributions to explain the fundamental features of heat and mass transfer occurring in the northern part of Lake Biwa throughout the year. Since it is well known that the thermal convection during the cooling period is the main mechanism of DO transfer from the surface to the lake bottom, the mixing processes caused by thermal convection are shown using the results of a 3D CFD simulation. Then, the electrolysis of water at the lake bottom for the restoration and DO recovery is introduced as one of the countermeasures proposed by Lake Biwa Environmental Research Institute, Shiga Prefecture. The simulation results of O2 bubble plumes with the dissolution into lake water are also shown under the conditions of laboratory and field experiments.

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The separation of solid particles from a fluid by means of gravity is an important operation in various engineering fields. The inclined-plate separator is often used to enhance the phase separation of the slurry in such fields as water clarification and bitumen production from oil sands. This paper presents the simulation study of the enhanced sedimentation in inclined vessel. In this study, we use a numerical simulation method based on the micromechanical fluid-particle system that couples the lattice-Boltzmann method (LBM) and the discrete element method (DEM). LBM is known to be a suitable technique for simulating fluid flow in complex and time-varying geometries with boundaries. On the other hand, DEM has attracted much attention among many researchers as a useful simulation technique for large deformation problems. With the coupling of both methods, the complex motion of solid particles in a fluid can be simulated. To verify this, the sedimentation behavior of a single circular particle is simulated in a fluid with different Reynolds numbers, and the results are compared with the finite element modeling. To investigate the relationship between the phase separation rate and the inclination angle of the vessel or the grain size distribution of the slurry, we attempted to simulate the settling behavior of multi-particle in a fluid. As a result, the global convection was occurred with increasing the inclination angle of the vessel. This phenomenon has also observed in many experiments. It cleared numerically that this convection contributes not only to the efficient draining of the fluid from the slurry, but also to the acceleration of the settling velocity. Based on these studies, it is confirmed that the numerical method coupled LBM and DEM becomes an important simulator for the evaluation of the inclined sedimentation.

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A gas-liquid two-phase flow in narrow channel is encountered in mini-scale devices, such as a separator for polymer electrolyte fuel cell. In the present investigation, detailed observation on pressure drop fluctuation characteristics in narrow channel were carried out. The test channel has a square cross section that has 2.0mm on a side. In order to investigate the influence of the return bend, we applied return U-shaped return bend and a return bend with a sharp 180-degree turn. Furthermore, in order to the influence of the wall wettability, water-repellent and attracting treatment were applied to the acrylic channel, respectively. In our previous study, in the straight section except as water-repellent channel, the fluctuation of the pressure drop could be correlated by the Lockhart-Martinelli parameter. On the other hand, in the return bend with a sharp 180-degree turn, it was hard to be correlated by the Lockhart-Martinelli parameter due to the centrifugal force. Furthermore, in the present investigation, even though in the return bend with a sharp 180-degree turn, it was cleared that the fluctuation of the pressure drop could be controlled by the wall wettability.

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