Wave transmission of deep-draft box-type bottom-detached breakwaters

Expanding human activity into offshore marine areas presents significant challenges. Protecting offshore structures and the areas within them from the destructive forces of large waves is of primary importance. Bottom-founded breakwaters are effective in shallow waters, whereas floating or bottom-detached breakwaters are more suitable for deeper waters. This study explored the transmission coefficient (k_t) of fixed box-type bottom-detached breakwaters (BDBs) with various dimensions under different wave conditions. A numerical wave flume based on Computational Fluid Dynamics (CFD) was validated using experimental measurements from a physical wave flume and employed to conduct a parametric study. The results indicated that the changes in wave steepness had a small effect on k_t of BDBs, while significant decreases in k_t were observed with the increase in relative draft (D_FB/L_w) and relative width (W_FB/L_w), where L_w presents wavelength. A predictive equation for k_t was derived from the numerical results and validated using the numerical data and the experimental data from present and previous studies. Within W_FB/L_w=0.004–0.43 and D_FB/L_w = 0.001–0.21, the proposed equation demonstrated considerable accuracy with a relative error within the range of (−20 %, 20 %). The Root Mean Square Errors (RMSEs) of the k_t predicted by the proposed equation and various experimental datasets were below 0.1.