An innovative ‘buoyancy-driven vertical piling breakwater’ is under development to protect harbor facilities behind the breakwater against tsunamis and high waves. This breakwater consists of rows of steel pipe piles and each pile consists of upper and lower steel pipes. Upper steel pipe is normally encased in lower steel pipe which driven into seabed and thus there small gap exists between upper pipes. When tsunami or high wave is predicted, the upper pipes quickly rise up to the water surface driven by the buoyancy of air supplied into the upper pipes.
A few experimental researches have been conducted on the hydraulic characteristics of this type of breakwater with gaps. In this study, hydraulic model experiments and numerical simulations were carried out to investigate the wave transmission through the breakwater and wave pressures acting on the upper pipes. As a result of the study, the breakwater's performance against tsunamis and high waves has been verified.