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It has become known that a vertical-barrier-type reflection dissipater is more effective thanthe conventional perforated-wall-type dissipater to reduce reflected waves from the sea walls, especially forcomparatively long waves. The dissipation mechanism of reflected waves is to enhance vortex flows around a verticalbarrier excited by the piston-mode wave resonance in the water chamber. In this study, wave force characteristics onthe barrier-type dissipater were examined extensively. Based on both the physical model tests and thetheoretical computations by use of the damping wave theory, the estimation method of peak wave forces on each wall and totalresultant forces was precisely discussed. For the practical design, effect of the vertical position of cappingplates above the water chamber on the wave reflection and uplift force was also examined experimentally.

A new typeofdissipaterofreflected waves from vertical walls was proposed. The sectionofthis dissipater is very simple, which comprises a vertical barrier on the front and a vertical wall on the back . Performance of this dissipater was examined experimentally and theoretically for both regular and irregular waves . The dissipation mechanism of reflected waves is to enhance the vortex flow under the front curtain wall by the piston-mode wave resonance in the water chamber. Major advantage of this new dissipater is to be able to decrease the breadth of the water chamber, say 1/10 of a wave length. Therefore, it is possible to dissipate much longer waves by the new dissipater having the same size as the conventional perforated type . Another advantage may be easy berthing of ships to the dissipater because of a flat front wall without any holes and slits.

and Mitsuteru JINNO It has become known that a curtain-wall type dissipater of reflected waves from vertical sea walls and breakwaters is more effective for comparatively long waves than the conventional perforated walls and breakwaters. The dissipation mechanism of reflected waves is to enhance vortex flows around a vertical barrier by the use of piston-mode wave resonance in the water chamber. However, for the sea with large tidal difference, it is concerned that effectiveness of the reflection dissipater may vary significantly with tidal levels because the draft depth of the vertical barrier changes with tidal levels.In this study, at first, variations of effectiveness of a curtain-wall type dissipater with tidal levels were clarified by both the physical model test and theoretical study. Secondly, in order to overcome such difficulties resulted from varying tidal levels, two different counter measures were proposed. Effectiveness of these measures was also examined theoretically and experimentally.

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