Kesayoshi Hadano

A study on dynamic motion and wave power in multi-connected wave energy converter

ABSTRACT Recently, with respect to structural strength and relevant analysis of a float-counterweight wave energy converter, it has been more improved than existing oscillating body type. This study is mainly focusing on dynamic motion and wave power generation of ‘multi-connected’ float-counterweight device by calculating the acquired generation amount. This advanced research was based on the float-counterweight device which was conducted through the waves up and down motion by setting up the wave chamber in the R&D Center of Mitsubishi Heavy Industries LTD. Most of all, it was obtained that the ‘multi-connected’ float-counterweight device would be more efficient and practical than the original one in terms of float displacement, wire tension and amount of wave power. Through this study, a basic data for design of wave chamber was utilised on advantageous condition under actual circumstances of the sea and then estimation of generation amount for the ‘multi-connected’ float-counterweight device was realised, compared to the original one.

Energy obtained by the float-type wave system

The authors are developing a wave energy converter which transfers wave motion into rotational motion of a shaft using a pulley, wire, float and counterweight. This paper gives a mechanical dynamic model convenient to design the prototype system. The calculation of the model was compared with a preliminary performance test held at a wharf and was found to be compatible. From the calculation of time series of various quantities, the importance of the float submergence during the work has been made clear. Time average of obtained electric power and the maximum values of various forces such as tensile force of wire have been evaluated for various conditions

EFFECT OF TIDAL RESIDUL CURRENT ON WATER EXCHANGE

Semi-closed bays suffer from water quality pollution frequently since ability of water exchange in semi-closedbays is poor. Many researchers and engineers have proposed the methods to improve water exchange in semi-closedsea. One of the easy methods for improving water exchange is to make a width of bay mouth narrow. According tothe study of Murakami et al., the water exchange was improved by using the narrow bay mouth if the tidal amplitudewas the same. In this study, the bay mouth shape in the model bay has been changed to improve the water exchange.The effects of the tidal residual currents on the property of water exchange have been studied.The ability of the water exchange in semi-closed bay become better as the tidal residual current energy increaseswhen the scale of the tidal residual circulation is small. On the other hand, the ability of the water exchange becomeworse as the tidal energy increases if the scale of tidal circulation is large.

WATER EXCHANGE AND VARIATIONS OF CONCENTRATION OF SUBSTANCES IN MYOJIN-IKE

1池が外海と連結した複数の連結湖沼からなる「明神池」で水質調査と流動観測を行い, 水質と水収支の両面から池内の汚濁長期化の機構を検討した. その結果, かなりの量の栄養塩類が外海と池, 池と池および池とポーラスメディアの間で出入りしていることが分かった. また, これらの水の出入りを考慮した簡単な水質予測モデルをつくった. 塩分, SiO2, PO4-PおよびT-Nの計算値は実測値と良好な一致を示した.

Flow Pattern around a Circular Cylinder Located in a Harmonically Oscllatory Flow

Flow pattern around a circular cylinder located in a harmonically oscillatory flow is visualized using the tracer particle method. The technique which enables to distinguish the directions of movements of the individual particles on a photo-print was employed. Both descrip-tions of the flow fields using the contour lines of vorticity and equivalent vortex strength, which are based on the resultant data of the velocity vector distributions, are presented.