Wavelet bispectral analysis and nonlinear characteristics in waves generated by submerged jets

Abstract

Nonlinear interaction dominates the whole process from wave deformation to breaking, and is one of the significant factors that may cause many unstable changes in waves. This study aims to indicate the nonlinear characteristics of waves generated by submerged jets. The time series of those waves under five dimensionless upstream water depths (l = 3.0, 4.0, 4.5, 5.0, 5.5) are measured experimentally. Moreover, the wave surface asymmetry, skewness, spectrum, and wavelet-based bicoherence are obtained. The results show that the amplitude of wave surface varies with the variation of measuring point position and upstream water depth. From the perspective of asymmetry and skewness, the wave surface varies from tilt forward to tilt backward along the propagation path, and the vertical tilt amplitude decreases gradually; meanwhile, except for few measuring points, it is basically negative skewness. It can be seen from the energy spectrum that the wave energy increases with the increase of upstream water depth and decreases with the propagation of wave surface. In addition, the wavelet-based bicoherence distribution shows that the energy transfer caused by the interaction between waves is weak. The findings can provide an improved understanding of the nonlinearity characteristics of waves generated by submerged jets.