长周期波浪激发矩形港池多模态共振研究

Research on the multi-mode resonance within a rectangular harbor induced by long-period waves

长和宽接近的矩形港池存在横向、纵向及横纵向混合共振模态。采用基于混合有限元的椭圆型缓坡方程数值模型模拟不同波浪入射角的低频波浪激发矩形港池的多模态共振,并分析不同平面布置形式的矩形港池模态响应特性。结果表明,斜向波浪会激发港池的横向共振模态,其放大因子受入射角度影响较大,而纵向共振模态的放大因子受入射角度影响较小。口门宽度对港池的共振模态个数与放大因子均有影响,具体为:随着口门宽度增加,各阶模态放大因子减小。口门位置对纯横向以及纯纵向共振的振荡模式有显著影响,而对横向纵向混合模态影响较小。各阶模态放大因子的大小和波节线与波腹线与口门的相对位置密切相关。

When a rectangular harbor’s length and width are close, there exist transversal resonance modes, longitudinal resonance modes and mixed transversal and longitudinal resonance modes. For the period range of low frequency wave, a numerical model is constructed by Hybird Finite Element Method based on elliptic mild slope equation. This paper aims to analyze the characteristics of multi-mode responses for a partially protected rectangular harbor with different layouts. The various factors include incident wave degree, and the width and location of harbor entrance. The numerical result shows: under the oblique wave action, the transversal mode emergeds, differing from the longitudinal resonance mode, and the transversal resonance mode’s amplification factor is significantly influenced by the incident wave degree. The width of harbor entrance can influence the quantity and amplification of the mode;when the width of entrance increases, the amplification factor will decrease. The location of harbor mouth can influence the oscillation mode of pure transversal or pure longitudinal resonance;conversely, the mixed transversal and longitudinal oscillation mode isn’t sensitive to it. The extent of impact of mouth location to each mode’s amplification is depend on the distribution of node lines and anti-node lines around the mouth.