Based on experimental and computational results of a ducted Darrieus-type water turbines, the applicability is proposed for utilizing hydro and tidal powers with extra-low head, which is abandoned because of poor cost-effectiveness as compared with conventional type turbines. The guiding principles for investigating the appropriate site and designing electric generation system are demonstrated quantitatively as useful data.

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The screw-type centrifugal pump has a wide flow passage to avoid the flow passage blockage with the congestion of solids. This pump has only one spiral blade added to a hub, the configuration of which is so complicated. It is difficult to predict the internal flow in the experiment and numerical studies have not been carried out sufficiently due to the complicated configuration. Therefore, the design method of this pump has not been established.
The authors succeeded in predicting the internal flow numerically using our own grid-generation system and a commercial code, TASCflow. In this study, the internal flow was predicted numerically under the five impellers with different meridian shapes in order to clarify their influence on pump performance. At the design point, the influences of impeller profiles were investigated from the numerical results of the internal flow field, the pressure distributions and the performance characteristics.

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This paper discusses the flow instabilities in a vaned diffuser by using CFD. A commercial code with the standard κ-ε turbulence model was used for the present work. It was found that the flow instabilities in the vaned diffuser; i. e., rotating stall, alternate blade stall, and asymmetric stall, could be simulated by the present calculations. These instabilities were observed in a range with negative slope of the pressure performance curve of the diffuser. In addition, the experiments were carried out for the purpose of visualizing the flow field under the stalled condition, and the results were compared with the calculations.

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