Numerical and Experimental Study on the Wave-Attenuation Effect According to the Height of a Two-Row Submerged Rectangular Structure

Coastal erosion, exacerbated by climate change and coastal development, presents increasing challenges for shoreline protection. This study investigates the effectiveness of submerged structures, specifically underwater breakwaters, in mitigating wave energy while supporting coastal ecosystems. The reflection and transmission coefficients of a two-row submerged rectangular structure at various heights were evaluated. Numerical simulations utilized the boundary element method (BEM) for potential flow analysis and computational fluid dynamics (CFD) for viscous flow assessment. Experimental validation was conducted in a two-dimensional wave tank at Inha University, measuring wave heights before and after interaction with the submerged structures. Results revealed that increasing structure height led to higher reflection coefficients and lower transmission coefficients. When the front structure was higher, the dissipation coefficient reached a maximum of 0.17. Maximum reflection and minimum transmission coefficients were observed under Bragg reflection conditions when the spacing matched half the incident wavelength. Discrepancies between CFD and BEM results were attributed to fluid viscosity effects. These findings underscore the potential of submerged structures to enhance wave attenuation, demonstrating that carefully optimized designs can significantly improve coastal protection.