Numerical study of solitary wave interaction with a vegetated platform

For shore protection under extreme wave climates, a simple platform, vegetation stems, and vegetation roots were used to assemble a new type of vegetated platform breakwater. To study the interaction of a solitary wave with it, a 2-D numerical model was conducted using a macroscopic approach based on the OlaFlow solver. The numerical model was well-validated using the experimental data in the literature. The simulated results indicate that the simple platform plays a significant role, and the vegetation plays a supporting role in wave damping. The vegetation roots tend to perform better than stems in reducing wave transmission. However, the roots always contribute to diminishing the wave elevation oscillation and sub-peak in the undulating tails. In addition, the velocity distributions of the green water and underflow above and below the platform are investigated to determine the individual drag coefficients for vegetation stems and roots, respectively. In detail, the effects of the relative incident solitary wave height, relative stem height and root height, vegetation density, and relative platform width on the hydrodynamic coefficients of vegetated platforms are discussed. Finally, empirical equations are proposed for predicting the wave transmission and reflection for a solitary wave propagating over the simple platform and the vegetated platform.