Numerical modeling of the interactions between waves and a Jarlan-type caisson breakwater using OpenFOAM

Abstract

In this study, a wave generation boundary capable of absorbing secondary reflections is embedded in an OpenFOAM-based numerical toolbox to model the wave-structure interactions of a Jarlan-type caisson breakwater (JTCB). Numerical simulations of wave structure interactions of a JTCB have been compared to experimental data where the reflection coefficient, the velocity field and the wave load of the JTCB, are analyzed in detail. It has been found that conventional two-dimensional (2D) simulation will underestimate the reflection coefficient, especially when the value of the nondimensional wave dissipation chamber length is in the range [0.12, 0.21]. This underestimation of the reflection coefficient could be related to an overestimation of the porosity of the perforated wall considered in conventional 2D structure simplifications. A porosity-equivalent 2D structure, whose porosity is the same as that of the three-dimensional (3D) structure, is presented and shown to effectively avoid this problem. In addition, in terms of wave loads, the agreement between the 2D simulation and the experiment has also been improved significantly using the porosity-equivalent 2D structure. Additionally, the interaction process, including the run-up on the back wall and the eddy formation process, is described via the changes of the velocity field and the free surface. Relatively good overall agreement between the calculated values and the experimental values is observed, indicating that this toolbox is useful and efficient for simulating wave-structure interactions of this kind. This study is expected to be useful to engineers concerned with the numerical modeling, preliminary feasibility assessment and conceptual design of JTCBs.