Three-Dimensional Hybrid Model for Wave Interaction with Porous Layer

A hybrid model combining Fully Non-Linear Potential Flow Theory (FNPT) based on the Finite Element Method (FEM) and the Unified Navier-Stokes equation, using the 3D Improved Meshless Local Petrov Galerkin method with Rankine Source (IMLPG_R), is developed to study wave interactions with a porous layer. In previous studies, the above formulations are applied to wave interaction with fixed cylindrical structures. The present study extends this framework by integrating a unified governing equation within the hybrid modeling approach to capture the dynamics of wave interaction with porous media. The porous layers are employed to replicate the wave-dissipating behavior of the structure. A weak coupling strategy is implemented within a designated buffer zone, wherein field variables from the 2D Fully Nonlinear Potential Theory (FNPT) simulations are transferred to the 3D Improved Moving Least Squares-based Petrov-Galerkin (IMLPG_R) model at each time step. This domain decomposition significantly reduces computational cost compared to a full 3D simulation by partitioning the domain into two subregions: the FNPT domain representing the far-field without structures, and the IMLPG_R domain encompassing the porous region. The Unified Navier-Stokes formulation is extended by incorporating additional drag forces governed by Darcy’s law to model the resistance introduced by the porous medium. A stationary background node framework is utilized for interpolation by fluid particles at each time step to accommodate the porous representation. To enhance numerical stability and accuracy, particularly in the presence of sloping boundaries, the Particle Shifting Technique (PST) is integrated into the IMLPG_R model. This implementation involves a modified version of the PST algorithm, where key parameters such as the weight function, velocity ratio, and radius of influence are optimized for IMLPG_R. This is the first time the application of 3D IMLPG_R for porous structure has been reported. Further, the model is subsequently validated against experimental data.