The interactions of porous vertical-cylinder array with incident waves and its performance as a breakwater are investigated by numerical simulations and medium-scale experiments. The interaction theory is based on linear potential theory for N bottom-mounted vertical cylinders and the porous and viscous effects are included through Darcy's law. The empirical relationship between plate porosity and porous parameter is obtained from a series of experiments. The numerical results agree well with the measured data. It is found that both transmitted and reflected waves as well as wave run-up and exciting forces are significantly reduced due to wall porosity. The results also show that the optimal design of seawater-exchanging breakwaters can be found through a systematic parametric investigation by controlling the size, number, porosity, and arrangement of circular cylinders.
Various types of permeable breakwaters have been proposed for the protection of coastal regions and construction sites. Recently, the requirement to improve seawater quality inside a harbor is increasingly implemented, and the permeable breakwater is appealing in this regard since it allows exchange of inner and outer waters (e.g. Jarlan, 1961, Isaacson et al., 1998). In this paper, the height and force reduction due to a breakwater composed of N bottom-mounted porous vertical circular cylinders is investigated. This type of porous breakwater can rapidly be installed by using pre-fabricated modules and it can be applied to temporary breakwaters for coastal construction or temporary harbors for amphibious military operation. The interaction of incident regular waves with a three-dimensional porous vertical circular cylinder was investigated by Wang and Ren (1994), in which the performance of a concentric two-cylinder system (exterior porous and interior solid) was solved analytically. They provide useful hydrodynamic information for the design of an offshore porous structure.
