No abstract

This paper considered the optimal arrangement on the assumption that multiple power generation systems are used in a row ahead of the realization of the wave power generation system using the DE (dielectric elastomer) which is expected to be popularized in the future. A power generation system using DEs was studied as a moored floating body, and tank tests were conducted. There are few studies on the influence of multiple moored floating bodies on each other. Those studies clarified the fluctuation, energy absorption efficiency, tension mooring force and quietness characteristics produced from differences in the arrangement of the floating bodies within the floating body group and so on utilizing the principle of double oscillating water columns. The purpose of this paper is to clarify the influence of floating body intervals and number of floating bodies on floating motion and mooring tension when a plurality of floating bodies are moored in a row perpendicular to the advancing wave direction. We also discuss the conditions of the large power generation system in actual sea areas using the DEs.

A simple experimental model of a power generation system was tested in a flowing water tank in order to investigate the performance and feasibility of a small hydroelectric generation system using DE (dielectric elastomer) transducer. The mass of DE material in the power generator module was only 0.1 g. The electric energy generated with a stroke of 10 mm was 12.54 mJ. An electrical energy of approximately 1.5 J per cycle of DE generators can be expected to be generated by scaling up this system, which is capable of being equipped with up to about 100 units of DE transducers. The water velocity was set at 0.30 to 0.70 m/s. This is a small flow, about the same flow as the water in a Japanese garden. This system was driven by Karman vortices in the wake of a cylinder fixed in the water flow. The characteristics of DEs can be utilized to produce electric power effectively. A wing, which is an important part in the generation system to convert fluid energy into mechanical energy, was set behind the cylinder. The wing oscillated due to the pressure caused by Karman vortices, resulting in stretching and contracting of the DE transducers, thus producing electrical power. Experimental results show that an average output power of approximately 31 mW was produced with a generation efficiency of about 66%, when the diameter of the cylinder is 60 mm, the span and chord length of the wing are 120 mm and 30 mm, respectively, the distance between the cylinder and the wing is 170 mm, and the velocity of the water flow is 0.50 m/s.

This paper aims to understand the kinetic characteristics and the hydrodynamic forces on a semi-planing typed high-speed vehicle during moving straight in calm water and in head waves. One of the features of this vehicle is considerable variation in its attitude due to the changes in the resistance value and propulsion performance associated with the change in a Froude number of the vehicle, and no reliable method has been established to evaluate this feature in advance. Therefore, we conducted free/captive towing tests at Froude numbers ranging from 0.03 to 1.8 using a scale model of the vehicle. The results show that the vehicle can move straight stably without unstable vibration even at high Froude numbers. In addition, we performed 3D unsteady RANS (Reynolds-Averaged Navier-Stokes equation) simulations for the vehicle with Froude numbers of 0.9, 1.2, and 1.8 in calm water and found that the RANS simulation could reproduce the experimental results relatively well with respect to the vehicle’s attitude, the drag coefficient, and the free surface shape around the vehicle.

This study focuses on the electric power generation performance of the system using the dielectric elastomer (DE). A simple experimental model is fabricated to test in a passing water tank in order to investigate the performance and feasibility of the small hydroelectric generation system using DE. This system is driven by Karman vortex in the wake of a cylinder fixed in water flow. The characteristics of DEs can be utilized for producing electric power effectively. The wing, which is an important part in the generation system to convert fluid energy into mechanical energy and is set behind the cylinder, vibrates due to the pressure caused by