The present paper investigates the wave interaction with a new modified Jarlan-type breakwater that consists of a perforated front plate, a solid back wall and a wave chamber between them filled with large diameter rock from the bottom to some distance under the water surface. The fluid domain is divided into two sub-domains and an analytical solution is developed by means of the matched eigenfunction expansion method. The present method is validated by comparing the numerical results for limiting cases with other results in published literatures. The major factors that influence the reflection coefficient and the wave force are investigated.
A perforated wall breakwater with a wave-absorbing chamber between the perforated front plate and the solid back wall is initially proposed by Jarlan (1961). Due to its significant effect of reduction of the wave reflection and the wave force, the Jarlan-type breakwater has received considerable attentions in the past 25 years. Various modified types have been proposed to enhance their hydrodynamic performances, and to meet the different requirements of engineering applications. The modifications mainly involve wave absorbers with two or multiple perforated front plates (Kondo, 1979; Twu and Lin, 1991; Li et al., 2003); partially perforated caisson breakwaters (Tanimoto and Yoshimoto, 1982; Li et al., 2002;); the perforated wall breakwater with internal horizontal plate (Yip and Chwang, 2000); the perforated breakwater with a rock-filled core (Isaacson et al., 2000); and perforated caissons with traverse walls (Teng et al., 2004). It is notable that the modification of Isaacson et al. (2000) is much convenient for constructing in practice. The study of Isaacson et al. (2000) has indicated that the rock fill reduces the wave force on the perforated front wall compared with the original type of Jarlan (1961), but increases the wave reflection and the wave run-up.