Wave Interaction With Jarlan-Type Perforated Wall Breakwaters

An original Jarlan-type perforated wall breakwater consists of a perforated front wall, a solid back wall and a wave absorbing chamber between them. In practice, the Jarlan-type perforated breakwaters are usually constructed with perforated caissons. The perforated wall breakwaters can effectively reduce the wave forces acting on, wave reflection from and wave run-up in front of the structures, which can resulted in a considerable reduction in the total costs of the project. Thus, the perforated wall breakwaters have been often used recently for harbor and coastal line protection in different countries.Many researchers have investigated the interaction of water waves with Jarlan-type perforated wall breakwaters. But, due to the complexity of this problem, the previous studies are still not sufficient. This paper presents further investigations on the interaction between water waves and Jarlan-type perforated breakwaters. There are three different major parts in the present study as follows.On the basis of the linear potential theory, the mathematical models for interaction between regular and irregular waves and a partially perforated caisson breakwater are developed by means of the matched eigenfunction expansion method and the finite element method. The partially perforated caisson is located on a rubble fill foundation and partially filled with rock in wave absorbing chamber. The reflection coefficient, the total horizontal and vertical wave forces as well as their phase difference on the structure can be evaluated using the present models. By comparing the predicted reflection and transmission coefficients of perforated wall structures with lots of experimental date, a simple method is presented to determine the porous effect parameter G of a thin perforated wall. The value of G is necessary for the practical application of present models. The present models are validated by comparing the predicted reflection coefficients and wave forces on the structure with experimental results. The main effect factors of reflection coefficients and wave forces are discussed. The predicted and experimental results of irregular waves are compared with the corresponding results of regular waves. An approximate method extended by the present irregular wave model is also given to predict the reflection coefficient of a partially perforated caisson breakwater located on a rubble mound foundation.Based on linear potential theory, an analytical solution of oblique wave interaction with partially perforated caisson breakwater with transverse walls are developed using the matched eigenfunction expansion method. The periodicity of the perforated breakwater along its length is used to obtain the analytical solution, and the evanescent modes are included in the eigen-expansion of the velocity potentials. The present solution is validated by comparisons with previous studies on different limiting cases. The main effect factors of the reflection coefficient, the normal total horizontal wave force acting on the caissons and the total horizontal wave force on the transverse walls are discussed. Main conclusions are presented for practical engineering application.Two modified Jarlan-type perforated wall breakwaters are proposed: Typeâ… is a fully perforated wall breakwater with an internal submerged horizontal porous plate; Typeâ…¡is a fully perforated wall breakwater with a submerged rock-filled core. By means of the matched eigenfunction expansion method, analytical solutions of regular wave interaction with these two new type perforated breakwaters are developed to calculate the reflection coefficients and wave forces on the structures. The present solutions are validated by comparisons with previous studies on different limiting cases. The hydrodynamic performances of the new structures are examined and compared. Some optimal parameters of the new perforated breakwaters are suggested for engineering design.