Model tests and CFD were carried out to find out the cause of cavitation surge in hydraulic power plants. In experiments the cavitation surge was observed at flow rates higher and lower than the swirl free flow rate, both with and without a surge tank placed just upstream of the inlet volute. An unsteady CFD was carried out with two boundary conditions：(1)the flow rate is fixed to be constant at the inlet volute, (2)the total pressure is kept constant at the volute inlet, corresponding to the experiments without/with the surge tank. The surge was observed with both boundary conditions at both higher and lower flow rates. Discussions as to the cause of the surge are made based on additional tests with an orifice at the diffuser exit, and with the diffuser replaced with a straight pipe.

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　潮流エネルギー変換装置の代表的なものであるサボニウス式水車は，水車起動のための水流初動速度が小さく回転トルクが大きいなどの利点はあるが，回転速度が遅く結果的にエネルギー変換効率が低くなるなどの欠点もある．
　本研究は，基本的な性能に優れる直立型サボニウス式水車に着目して，その変換効率を高めるため新規に水車の周囲に流向制御板を取り付けるなど増速装置を付設する工法を提案すると共にその有効性について明らかにする．既に著者らは，外輪型流向制御板を導入することで，直立型サボニウス式水車による潮流エネルギーの変換効率が有意に改善できることなどを示した．ここでは，の支持構造や実海域を想定した場合などを含め，さらなる潮流エネルギー変換効率の改善工法について検討を加えたので，その成果について紹介する．

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It is proposed to incorporate 1DCAE into a virtual engineering system in mechanical system design. In order to continue using an established virtual engineering system for a long time, it is necessary to modify it in line with the evolution of CAD, CAE, analysis, and evaluation technologies. If information in CAD or the like is coded directly in the system, it will be necessary to make changes to the system. Meanwhile, if the evaluation method, etc. is changed, the user interface of the system may need to be changed. These changes require software engineers and are costly and time-consuming.

In this paper, we propose that the elements in the system be independent, that the relationship between each element be defined by JSM, and that 3D-CAD be used for user interfaces. This will allow even those without software language skills to update the technology and create a long-lasting virtual engineering environment.

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A contra-rotating turbine system is theoretically torque free, since the second blade counters the first blade torque. In this study the contra-rotating turbines are adopted as an ocean current power generator. In this paper computational study is performed to investigate the wake flow characteristics of contra-rotating configuration. In additional to calculating the hydrodynamic forces and power outputs by using Computational Fluid Dynamics (ANSYS Fluent 18.0).

In this study the flow generated by the ocean current turbine has been calculated. The purpose is to study how a contra-rotating ocean current turbine design. This method is validated by comparing with experimental results.

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The environmental problem and related energy problem are recently the serious problem all over the world. The renewable energy is now highlighted as one of the solution to the problem. The possible use of ocean current as an energy resource begins to draw attention in the renewable energy. In this paper, horizontal axis ocean current turbine performance estimated by Computational Fluid Dynamics is carried out. The numerical estimation method is able to calculate not only a turbine performance characteristics but also turbine with shroud (the collection device) performance characteristics. This method is validated by comparing with experimental results.

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We have shown that the conversion efficiency of tidal current energy by a vertical Savonius water turbine is significantly improved by introducing a new guide vane device around it. In the target site of a tidal current power plant, typically Kurushima Strait in the Seto Inland Sea, the site usually faces to comparatively wide sea area on both sides of the narrow channel. Therefore, wave actions on the tidal current power plant must be examined from both the points of structural stability and energy conversion efficiency. In this study, the influence of wave actions on the conversion efficiency of tidal energy was examined experimentally through the use of combined flow field of waves and tidal currents. In addition, effectiveness of a vertical Savonius water turbine as a wave energy extraction device was also examined.

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Tidal current energy is one of the most important future energy, clean, renewable and predictable. We are studying the Darrieus turbine that has omnidirectional characteristic in the reciprocating tidal current in a narrow channel. To enhance the performance of the tidal turbine, we propose adding a pair of appendage structures near the turbine, because the power of the turbine is proportional to the cube of the current velocity.In this report, we first present the performance of the simple Darrieus turbine by model tests in a circulating water channel and CFD calculations. For the validation of CFD calculation, the torque variation and the power coefficient of Darrieus turbine are compared with experiments. For the determination of the shape of a pair of appendage, the CFD results for several shapes of the a pair of appendage are compared. It is found that the small difference in shape of a pair of appendage is not important for the final performance, so that we adopt the arc shape a pair of appendage. We compare the power coefficients of the Darrieus turbine with/without a pair of appendage by the experiments.

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Phenolic bearings have been used as water lubricated resin bearings for the main shaft of hydroelectric power turbines since around 1970, contributing to the reduction of environmental pollution. They enable improved power generation efficiency and compact equipment design due to their low coefficient of friction and high load capacity under water lubrication. Recently, a new phenolic bearing with dramatically small dimensional changes due to water absorption, which has been a problem, has been developed. The new material shows excellent self-lubricating property not only under fluid film lubrication conditions but also under boundary lubrication conditions where it is difficult to form water lubrication film when a turbine starts and stops.

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