Bragg Resonance by a Pair of Sinusoidal Seabed Patches With Floating Funnel Breakwater

Abstract Bragg scattering by a floating funnel breakwater (FFB) is evaluated in the presence of a pair of seabed patches within the framework of small-amplitude wave theory. The FFB consists of a pair of vertical walls near the free surface, with a pair of arc plates installed at the keel in opposite directions to create a chamber. A semi-empirical quadratic discharge equation is applied to the FFB to incorporate the influence of wave height on energy dissipation. A pair of seabed patches on the seaside of the FFB is being deliberated to understand the effects of gap resonance. The dual-boundary element method is employed to assess the performance of FFB in the presence of a pair of sinusoidal seabed patches. Scattering coefficients and instances of Bragg reflections by (i) a single sinusoidal seabed patch, (ii) a pair of seabed patches, (iii) an FFB with a single patch, and (iv) an FFB with a pair of seabed patches are reported. Bragg resonant reflection is observed with an increase in the number of seabed ripples and patches with multiple instances of zero reflection. A mono-Bragg peak and a pair of peaks are observed for a single-seabed patch and a pair of seabed patches, respectively, with multiple sub-peaks. Bragg peak magnitude correlates with ripple number and amplitude. The FFB minimizes wave transmission through energy damping, while seabed ripples enhance wave reflection (Bragg peak).