The Karman vortex induced vibration (KVIV) is observed over a wide range of conditions, and has been regarded as a negative phenomenon until now since it has caused many accidents. Therefore a lot of researches have been conducted to predict and to avoid it. Recently, however, KVIV is regarded as a process to convert energy of natural flows into mechanical energy, and techniques for electricity generation utilizing it are proposed. The electric power of this method is smaller than that of wind and water turbine generations, but this method has possibility to become a smaller and more maintenance-free apparatus than rotary machines. In earlier works, we found that the trailing vortex shed periodically from a cruciform two-circular-cylinder system, and that it induces a cross flow vibration on the upstream cylinder (TVIV) over a wide velocity range, which becomes broader by replacing the downstream cylinder by a strip-plate. Because of this character, an electricity generator utilizing TVIV should be effectively applied to rivers of which velocity usually varies largely. The purpose of this work is to develop a technique to generate electricity utilizing TVIV in water flow. Experiments using a water tunnel and an open-surface water channel are conducted to know conditions of the maximum electric power and to test the performance in a river. The optimum gap-to-diameter ratio is 0.22 since the cylinder vibration amplitude is largest. The optimum resistance of the circuit is the value which makes the virtual damping due to electricity generation nearly equal to the structure damping. The performance test in the water channel shows that the open surface and the turbulence in flow have little influences on the cylinder vibration amplitude and the synchronization velocity range of KVIV. However, TVIV is not observed, maybe because of the large aspect ratio.

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