ABSTRACT:

Wings, which are attached to near ship-bow bottom, is generally called bow wings. By using a bow wing, we can reduce added resistance of ships due to waves and ship motions. As even a fixed bow wing shows those performances, a movable wing is expected. To design the wings movable, we investigated three subjects. 1) Estimating method of an angle of attack of a bow wing by using ship's bottom pressure. 2) Proposal for approximation method of the integration, the convolution integral of the bottom pressure and kernel function is needed for estimating it in time domain. 3) A method to avoid a stall of a bow wing.

INTRODUCTION

Various researches on wave energy utilization have been made. For that purpose the usefulness of a fixed bow wing attached to a ship hull have been reported, and also studying a movable bow wing is requested. When we control a bow wing whatever the object is to reduce a ship motion and/or absorb wave energy, it is indispensable to estimate an angle of attack of a bow wing. Based on a linear relationship between a ship's bow bottom pressure and an angle of attack can be used for control signal. Then, by using the measured bow bottom pressure, we propose a new control system of a bow wing for converting wave energy to a thrust. For an actual control system, we must integrate two subjects in time domain.

THRUST GENERATED BY CONTROLLED BOW WINGS

The coordinate systems are defined as shown in Fig. 1 and Fig. 2. A wing fitted at the bow of an oscillating ship body with forward velocity has the characteristics of an oscillating wing. By multiplying the quasistatic lift with the oscillation influence coefficient, one can obtain the lift of this bow wing pair(Naito, S. (2003)).

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