Generation of highly nonlinear irregular waves in a wave flume experiment: Spurious harmonics and their effect on the wave spectrum

Abstract Spurious harmonics generation can occur in wave basins when strongly nonlinear waves are generated with linear maker theory. For regular long crested waves, the phenomena is known to cause a beating pattern for amplitude of higher harmonics, while irregular effect often thought average out. We here report on recent experimental results spurious harmonic highly waves. Long at two depths considered. find systematic distortion spectral shape which non-uniform space. The occurs and super region spectrum strongest smaller depth. analyze phenomenon through re-computations fully model further application four-phase separation. next extend analysis allow separation third- first-order content first-harmonic field, by computation different amplitudes. numerical resembles measured closely shows that super-harmonic large extent property second-harmonic field. Further, match between original target shown improve removal extracted third-order contribution. observed frequency thus be explained this Returning second-order we demonstrate field associated reproduced Sharma Dean theory inclusion reconstructed from generation. Finally, forces discussed quantified. force peak exceedance probability less influenced than shape. link phase speed makes them arrive later main packet leads limited enhancement local peaks.