Numerical and experimental investigation of hydrodynamic characteristics of solitary waves interacting with mangroves

With the increasing likelihood of extreme wave events due to climate change and sea-level rise, mangrove forests provide an effective nature-based solution for coastal protection. This study investigates the solitary wave attenuation effect by mangroves via laboratory tests and numerical simulations based on the immersed boundary method. The wave attenuation coefficients are compared for a variety of spatial configurations of mangrove zones under different wave conditions. The laboratory results indicate that wave attenuation coefficients are influenced by mangrove zone length and, to a lesser extent, mangrove zone density. Different layouts of the mangrove zones lead to similar attenuation effects within the tested parameter ranges. Moreover, the averaged dissipation spectra reveal the spectral bands where dissipation is concentrated for various wave parameters and case combinations. With detailed numerical flow fields, wave-mangrove interactions are quantitatively analysed. Increasing mangrove zone density can steepen the decay of mechanical energy flux at different cross-sections, whereas increasing zone length only contributes to the total dissipated energy without apparently changing the decay rate. Furthermore, the temporal and spatial distributions of enstrophy are examined and related to the streamwise velocity wavenumber spectrum, to reveal the spatial characteristics of kinetic energy redistribution. These findings may provide a quantitative reference for assessing mangrove-based coastal hazard mitigation.