Analysis of an Ability for Periodic Wave Generation of Bottom Wavemaker using a High-order Spectral Method

In this study, the characteristics of periodic waves generated by a bottom wavemaker were investigated using a high-order spectral (HOS) method, a fully nonlinear model capable of simulating wave generation by a moving bottom. The numerical results indicate that the non-dimensional wave height (H/S) of the generated waves reaches its maximum when the non-dimensional length of the wavemaker (b/λ) is 0.7 for a triangular bottom wavemaker, and 0.5 and 1.5 for a rectangular bottom wavemaker. An examination of the wavemaker’s capability revealed that it can successfully generate waves with a non-dimensional wave height of 0.5 or greater and a well-defined sinusoidal shape within the relative water depth range of 0.055 < h₀/λ < 0.2 when the nondimensional stroke length (S/h₀) is 0.1 or less, and within the range of 0.091 < h₀/λ < 0.2 when S/h₀ is 0.1 or greater. Conversely, when the relative water depth (h₀/λ) is 0.05 or less, higher-order harmonic components are concurrently generated due to strong nonlinearity, making it difficult to accurately reproduce the sinusoidal wave shape.