The seawater exchangeable breakwaters may be useful to exchange the seawater and supply oxygen for improvement and preservation of seawater and sediment quality. In this study, we propose a modified curtain-wall type seawater exchangeable breakwater and examine its performance by physical model tests and numerical simulations. Both the damping wave model and the volume of fluid method are employed in numerical simulations. The main feature of a modified breakwater is to place a submerged horizontal plate in the water chamber, which plays an important role to reduce both the reflected and transmitted waves for the wide range of wave frequency. It is also found out that the modified breakwater can cause aeration and vertical mixing by wave actions.

Seawater exchange breakwaters may be useful to keep the water quality and also to maintain theseabed condition in a harbor. We have already presented a new type of seawater exchange breakwater , which is able to induce outgoing mean current to the offshore by the wave excited vortex motion in the breakwater . In this study, we examine the effectiveness of the breakwater in harbors, such as wave sheltering effects and water exchange abilities . Two different harbor models are adopted to test the effectiveness of the breakwater . Performance of the breakwater in the harbor is also compared to the previous two dimensional results in the vertical plane . It is seen that the new breakwater is effective in harbors in the same way as the two dimensional wave field ..

The flow induced forces acting on a cube and a strip roughness placed submerged on the bed in open channel flow were measured by using the three-component load cell. The flow around the cube were measured by using a laser Doppler anemometer (LDV) and a particle image velocimeter (PIV) and were simulated with a k-ε turbulence model. The drag and lift force coefficients of the cube and strip roughness in the open channel flow with free surface become large with increase of the ratio of cube height h and water depth d (h/d). The equivalent roughness k s for the strip roughness were also estimated by the measured drag forces acting on a strip roughness.