Numerical investigation of triadic interactions during wave propagation over a submerged bar using a fully nonlinear numerical wave tank

This study models wave propagation over a submerged trapezoidal bar problem with a Higher Order Boundary Element Method (HOBEM) based on a two-dimensional fully nonlinear numerical wave tank (NWT). A Mixed Eulerian-Lagrangian technique is implemented, and the NWT is validated using the experimental results available from the existing literature. A numerical investigation is conducted on the individual wave harmonics as it propagates across the numerical wave tank over the submerged bar. The amplitude spectrum is obtained from the time histories of wave elevation across the tank at various locations over the trapezoidal bar and compared with the experimental results. The redistribution of the energy spectrum across the domain is recorded as the regular long wave propagates and undergoes deformations because of shoaling followed by de-shoaling. This phenomenon is investigated using a higher-order statistical analysis method viz. Bispectrum. The mechanics of the redistribution of energy among the harmonics is quantified through bispectrum analysis. Further, regular and irregular wave propagation over the submerged bar in the presence of the following and opposing currents is simulated. The effect of current is studied using the amplitude spectrum and the harmonic interaction for each case is compared using bispectrum analysis.