A theoretical analysis using an integral equation derived for the unknown horizontal velocity component in a previous wall is proposed for estimating the reflection coefficient of a wave dissipating breakwater with multiple vertical pervious walls where waves strike the structure obliquely. Various factors related to wave and structural conditions having influences on the reflection coefficient are investigated for a double vertical slotted-walls breakwater. The optimum structural conditions to minimize the reflection coefficient are also discussed in the paper.
Impervious-type upright wave dissipating structures anticipating low reflection had their beginning in the 1960s when Jarlan (1961) first proposed a perforated caisson. In Japan also, structures of this type gradually began to be adopted for breakwaters, quays and revetments from the 1970s, and at the same time, much research and development (Kondo et al., 1983) came to be done. With the advances made in subsequent research and development, it began to be pointed out that with a structure having a single chamber as proposed by Jarlan, when structure width becomes definite, the range of wave length at which there is wave dissipating capacity will be limited and the reflection coefficient will vary tremendously depending on the wave period. Ijima, Okuzono and Ushifusa (1977) and Sawaragi and Iwata (1977) investigated the basic wave dissipating characteristics of an upright wave dissipating structure having double chambers to make improvements regarding this problematic point. As a result, features were revealed such as that with a form having double chambers, compared with one having a single chamber, there is no great change in wave dissipating effect even with changes in wave characteristics such as wave height and period, with moreover, wave dissipating capacity high, and even with a narrow structural width ample wave dissipating capacity can be obtained.
