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The core melt accidents at Fukushima Daiichi Units 1-2-3 have occurred due to the tsunami of the Great East Japan Earthquake at March 11, 2011. Now a coolant of approximately 100t is injected into each Reactor Vessel (RPV) in order to cool the fuel debris, and a part of the coolant leaks out from the water. The contaminated water is collected, and it is stored in the contaminated water storage tanks more than approximately 1,000 and the total amounts of coolant exceeds 1,000,000 t. Although the contaminated water is purified by ALPS, it is still in high nuclear pollution density. According to the homepage of Nuclear Regulation Authority (NRA) in Japan, the storage tanks have been placed on the concrete bed without any anchor. Tokyo Electric Company (TEPCO) reported to NRA in 2015 that the design acceleration used for the overturning evaluation of the tanks have 0.3G. At the Fukushima Daiichi Power Station in the Great East Japan Earthquake, the maximum horizontal acceleration was 0.6G, the maximum vertical acceleration was 0.326 G at the time of the Great East Japan Earthquake. Even if an earthquake that is a fraction of this earthquake comes back, there is a possibility that this tank will fall over. The temporary special design guideline is adopted. These tanks have already stored the contaminated water for 6 years. However, it is thought that the more long term countermeasures is necessary for preventing the contaminated water from flowing out into the Pacific Ocean when another great earthquake will attack this area in future. In this paper, we propose a drastic structure to add a foundation without causing ground to the present tank. In the past, the member fastening the steel plate of the upper structure of the tank and the concrete of the lower structure is a foundation bolt, but this time it is a stud welded to the tank side plate. This made it possible to flexibly design and reinforce the foundation itself even after tank installation.

When flexible pipes are subjected to internal flow, the pipes lose stability by flutter and divergence in increasing the fluid velocity. In addition, they also lose stability when they are subjected to external annular axial flow. In this paper, the pipe is subjected to internal flow and external flow at the same time. The dynamic stability of a double wall pipe structure system subjected to an internal flow and an external flow simultaneously is thought to be one of the important pipe structures for the development of a piping system in the field of ocean mining, and in the field of fluid energy generation, and so on. In this paper, the pipe structures are assumed to be composed of the cantilevered elastic tube structure. For the analysis of the internal flow, the conventional inviscid stability analysis method is applied. For the analysis of the external annular axial flow, both the viscous solution using the Navier-Stokes equation of motion and the ideal fluid solution which viscous influence are added to are applied. Changing the flow direction and the fluid velocity as for the internal flow and the external flow, the dynamic stability of the double wall pipes is investigated and discussed. Moreover, changing the flow rate and the density of a fluid and a structure, these effects on the stability of double wall pipes are investigated.

When slender pipes are subjected to internal flow, the pipes lose stability by flutter and divergence in increasing the fluid velocity. In addition, they also lose stability when they are subjected to external annular axial flow. In the development of a piping system in the field of ocean mining, and in the field of fluid energy utilization, and so forth, the double walled pipe structure system subjected to an internal flow and an external flow simultaneously is thought to be one of the important pipe structures. In this paper, the pipe structures are assumed to be composed of the cantilevered beam structure which shows the complicated dynamic behavior than the other supported conditions. For the analysis of the internal flow, the conventional inviscid stability analysis method is applied. For the analysis of the external annular axial flow, both the viscous solution using the Navier-Stokes equation of motion and the ideal fluid solution which viscous influence is added to are applied. Changing the flow direction and the fluid velocity of the internal flow and the external flow, and the specifications of modeling, the stability of the double walled pipes is investigated and discussed.Copyright © 2015 by ASME

When a flexible plate of machines and structures is in axial flow, increasing the flow velocity induces the dynamic instability. Also, the similar instability occurs for a thin film wound to a coil form and a band saw driven with high transport speed even if we consider there is no effect of fluid. However, if a flexible plate is very light, and the rigidity is weak, the dynamic instability of a plate is thought to be affected both by the transport speed of plate and by the surrounding fluid. In this paper, the stability analysis is performed using the velocity potential based on the boundary conditions between the surrounding fluid and the plate. The numerical studies are performed as for a cantilevered plate. The case of an axially moving plate in a still fluid, the case of a stationary plate subjected to an axial flow, and the case of an axially moving plate in neglecting the effect of surrounding fluid are examined. And, the effect of the transport speed of cantilevered plate on the dynamic stability is discussed. Furthermore, another stability analysis is also performed by using the non-circulatory aerodynamic theory, and the numerical analysis results are examined and discussed.Copyright © 2015 by ASME

As the flexible plates, the papers in printing machines, the thin plastic and metal films, and the fluttering flag are enumerated. In this paper, the flexible plate is assumed to be stationary in an axial flow although both the stationary plate and the axially moving plate can be thought. The fluid is assumed to be treated as an ideal fluid in a subsonic domain, and the fluid pressure is calculated using the velocity potential theory. The coupled equation of motion of a flexible cantilevered plate is derived in consideration of the added mass, added damping and added stiffness, respectively. The velocity potential is obtained by assuming the unsteady axial fluid velocity to be zero at the trailing edge of a flexible cantilevered plate, neglecting the effect of a circulation. The complex eigenvalue analysis is performed for the stability analysis. In order to investigate the validity of the proposed analysis, another stability analysis is also performed by using the non-circulatory aerodynamic theory. The comparison between both solutions is investigated and discussed. Changing the velocities of a fluid and the specifications of a plate as parametric studies, the effects of these parameters on the stability of a flexible cantilevered plate are investigated.Copyright © 2014 by ASME

A herringbone-grooved gas-lubricated journal bearing can rotate silently at high speed with low friction, and moreover it can be small-sized. In this paper, the equation of motion of a herringbone-grooved gas-lubricated journal bearing is derived using the gas force which can be obtained by applying the Navier-Stokes equation to the grooved and the ridged parts of a journal. The stability analysis is performed by using the analysis method by Routh-Hurwitz, the root locus of complex eigenvalue analysis, and the transient time history response analysis. The physical meanings of the stability charts which have not been explained sufficiently in the conventional studies are clarified by considering the forward whirling motion and the backward whirling motion, and the more reasonable stability charts are proposed. In addition, it is reported that the present analysis results show a good agreement with the already reported experimental results. Furthermore, the parametric studies as for the specification of gas-lubricated bearing are performed, and it is shown that the stability charts are affected by the change of specifications intricately.Copyright © 2014 by ASME

The dynamic stability of a flexible plate subjected to a parallel flow is investigated when it moves in a flowing fluid. As the flexible flat plates, the papers in a high speed printing machine, the papers discharged by a paper machine, and the thin plastic and metal films, the fluttering flag and the oscillating doom roof caused by wind are enumerated. The fluid is assumed to be treated as an ideal fluid in a subsonic domain, and the fluid pressure is calculated using the velocity potential theory. The fluid-structure coupled equation of motion of a flexible flat plate supported simply at the both ends is derived into consideration with the added mass, added damping and added stiffness of a fluid, respectively. In addition, the effect of tension acting on a flexible plate, the influence of velocity of a moving plate and that of a fluid velocity, are also included into the coupled equation of motion respectively. The eigenvalue analysis is performed for the dynamic stability analysis. Changing the velocities of a plate and a fluid, and the specifications of a plate as parameter studies, the influences of these parameters on the dynamic stability of a plate are clarified. It is made clear that the plate moving in a still fluid becomes unstable at slightly lower velocity than the stationary plate subjected to a parallel flow. Moreover, it is found that the present solution shows a good agreement with the already reported experiments in which the flexible flat plate was a paper.Copyright © 2013 by ASME

The stability of nonconservative system of a beam is investigated when an elastic beam is subjected to follower forces. The mathematical formulations for a conservative system and a nonconservative system are established regarding to a uniform cantilever subjected to a concentrated force and a uniform distributed force axially. The displacement of a uniform cantilever is assumed to be obtained by superposing the modal functions which are normal modes in a vacuum, and is estimated by applying the Galerkin’s method. Changing the forces, the eigenvalue analysis is performed, and the root locus is calculated for the stability analysis. And, the relationship between forces and frequencies for the undamped system and the damped system of the uniform cantilever subjected to a concentrated force and a uniform distributed force is investigated. When the system is considered to be conservative, the divergence phenomenon is confirmed to appear first. On the other hand, when the system is considered to be nonconservative, the flutter phenomenon is confirmed to appear first although the critical force becomes high. And, by changing the structural damping, the destabilized effect due to the damping is confirmed when an elastic beam is subjected to follower forces.Copyright © 2012 by ASME

Motion and vibration analysis of a roller coaster running in a 3D trajectory is carried out. The equation of motion of the roller coaster is derived in which the restriction in the trajectory is dealt with by using differential-algebraic equations (DAE) method. The effects of a parameter variation of the roller coaster to the vibration of the passenger are investigated in simulation analysis. The simulation result shows that when the parameter associated with the stiffness of the wheels of the roller coaster decreases, the passenger’s vibration increased. In addition, it shows that the discontinuity of the rate of increment of the trajectory induces large vibration.