双色波激发细长港内低频振荡的物理试验研究

Physical experimental study of low-frequency oscillations in narrow-long harbor induced by bichromatic wave

通过物理试验研究双色波传入细长港池并激发港池低频振荡,合理的试验布局降低了波浪二次反射对造波机的影响问题。利用快速Fourier变换和小波变换方法分析双色波在港内的幅频响应以及波浪能量的时-频分布情况,并利用小波二阶谱分析港内波浪不同成分之间的非线性相互作用过程。结果表明:当双色波短波频率对应港池不同共振频率时,通过波浪非线性相互作用产生的二阶长波在港内响应幅值不同;短波频率对应港池较低共振频率时,波浪会在港内聚集更多的能量;二阶长波以及高次谐波与双色短波之间呈复杂的非线性能量传递过程。

The bichromatic waves propagation into a narrow-long harbor excites low-frequency oscillations inside the harbor,and the influence of wave secondary reflection on the wave maker is reduced due to reasonable arrangement of physical model experiment.Concurrently,reasonable experiment layout reduces the influence of wave re-reflection on wave maker. Fast Fourier transform and wavelet transform are adopted to investigate the amplitudefrequency response of different bichromatic waves and the distribution of wave energy in time-frequency domain.The non-linear interaction process between different components of waves is also investigated by employing the waveletbased bispectrum. The results show that: when the short wave of bichromatic waves has different resonance frequencies corresponding to the harbor,the sub-harmonic frequency wave amplitudes generated by wave nonlinearity are different in the harbor;when the short wave of bichromatic waves corresponds to the lower resonance frequencies of the harbor,the waves would gather more energy in the harbor;the non-linear transfer processes of wave energy are revealed between sub-harmonic frequencies and superharmonic frequencies in wave components and the short wave frequency.