Water hammer pumps can effectively use the water hammer phenomenon for water pumping. They are capable of providing an effective fluid transport method in regions without a well-developed social infrastructure. The results of experiments examining the effect of the geometric form of water hammer pumps by considering their major dimensions have been reported. However, these conventional studies have not fully evaluated pump performance in terms of pump head and flow rate, common measures of pump performance. The authors have focused on the effects on the pump performance of various geometric form factors in water hammer pumps. The previous study examined how the hydrodynamic characteristics was affected by the inner diameter ratio of the drive and lift pipes and the angle of the drive pipe, basic form factors of water hammer pumps. The previous papers also showed that the behavior of water hammer pump operation could be divided into four characteristic phases. The behavior of temporal changes in valve chamber and air chamber pressures according to the air volume in the air chamber located downstream of the lift valve was also clarified in connection with changes in water hammer pump performance. In addition, the effects on water hammer pump performance of the length of the spring attached to the drain valve and the drain pipe angle, form factors around the drain valve, were examined experimentally. This study focuses on the form of the lift valve, a major component of water hammer pumps, and examines the effects of the size of the lift valve opening area on water hammer pump performance. It also clarifies the behavior of flow in the valve chamber during water hammer pump operation.

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By a theoretical study with an one-dimensional model and an experimental investigation with conical diffusers, it has been found that the diffuser effect of the draft tube cause cavitation surge. The present study focuses on effects of the swirl inflow and its velocity distribution at the inlet of the diffuser. Experimental and numerical investigations are carried out with a conical diffuser and a two-stage swirler at the inlet. Results show that the inlet circumferential velocity distribution affects the wall pressure distribution, and finally occurrence of the cavitation surge.

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This study is aimed at development of the extra-low head water turbine for an open channel from a viewpoint of using effectively unused hydropower energies, such as an irrigation channel. Then, paying attention to the cross-flow runner, authors eliminated the casing and tried the application as a water turbine for an open channel. In this paper, water turbine performance, the flow situation characteristics, and the flow in the runner were experimentally investigated about the water turbine. As a result, the following facts became clear. When initial depth of water is shallow, turbine efficiency is high in a low rotation region, and when initial depth of water is deep, turbine efficiency is high in a high rotation region. Unlike the runner in which the cross-flow runner which does not have a bottom plate has a bottom plate, air bubbles do not stagnate between blades to blade. Moreover, winding up of the water by a blade does not arise. Therefore, in a wide range rotation region, an output and turbine efficiency improves substantially.

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