The tidal and sea current turbines are one of potential utilization of renewable energies as well as offshore wind ones. However they possibly produce efficiently electricity because of high density of water to air and more steadiness of flow to winds, hydro turbine generation system is less employed than wind one. We are studying an application of Straight Wing Vertical Axis Hydro Turbine Generation Systems in the tidal current. This paper presents the results of hydraulic model test using 2-dimensional channel and field test.

The tidal and sea current turbines are one of potential sources for utilization of natural energies. When applying them to the actual sea, it is necessary to evaluate how much increase of hydro forces acting on the turbines, and to examine if any drop or increase of electrical generation due to waves. Therefore, we conducted 2-dimensional tank tests in the current, both wave and current to measure the loads, rotational speed and output volts induced in the 1/100 scale turbine. As simple stream tube theory often apply to analyze a turbine in uniform flow, so we use it for the analyses of hydro forces and energy outputs of the turbine in coexistence of wave and current. The paper presented the comparison the model tests results with the theoretical calculation to clarify the effects of waves to the turbine.

In offshore pipeline constructions, high productivity is required to minimize pipe laying cost. One of the most significant methods for achieving higher productivity is to reduce the welding defects, which require much repair duration.Recently, the acceptable level of welding quality, especially the root pass, becomes higher and higher. This means minimizing fitting misalignment between both pipe ends is required to get rid of welding defects triggers. On the contrary, the tolerances of commercially manufactured pipes have been same and their shape fluctuation between both pipe ends is not ideal for welding conditions. To solve this problem fundamentally, the authors have developed the pipe end round forming equipment to aim at perfect fitting alignment between both pipe ends for girth welding.The shape equalization between both pipe ends by this forming equipment, will lead to not only elimination of welding defects but also reduction of pipe fitting duration prior to girth welding and will contribute to improve pipe laying productivity.

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