N波诱发的瞬变港湾振荡的数值研究

摘要

To investigate transient oscillations excited by tsunamis, the transient oscillation phenomena inside a long and narrow rectangular harbor induced by isosceles leading-elevation N-waves and isosceles leading-depression N-waves were simulated with a fully nonlinear Boussinesq model.On the basis of a normal-mode decomposition method, the response amplitudes of different resonant modes of the harbor were decomposed quantitatively.Then, the effects of the amplitude and the type of the incident N-wave on the relative wave energy distribution inside the harbor were studied systematically.Results show that for the given harbor and the given range of the incident wave amplitude, when the incident wave amplitude is small, the relative wave energy distributions inside the harbor excited by the abovementioned two types of the N-waves are almost identical, and almost all the wave energy concentrates on the lowest few modes.With the increase in the incident wave amplitude, the proportion of the wave energy that is distributed over the higher modes increases, and the energy distribution inside the harbor becomes uniform.The resonant mode that possesses the highest wave energy shifts gradually from the lower mode to the higher one.Compared with the isosceles leading-elevation N-waves, the wave energy distribution inside the harbor excited by the isosceles leading-depression N-waves is more uniform.%为了研究海啸波诱发的瞬变港湾振荡问题,本文采用一组完全非线性Boussinesq模型,模拟了由波峰在前和波谷在前的两种类型的等边N波入射诱发的狭长矩形港内的瞬变港湾振荡现象.基于正交模态分解法,定量分离了港内不同共振模态的响应幅值,并系统研究了入射N波类型和入射波波幅对港内相对波能分布的影响.研究表明:在本文所研究的特定港口和入射波波幅范围内,当入射波波幅较小时,以上两种类型N波诱发的港内相对波能分布几乎完全相同,并且波能几乎都集中在最低的几个共振模态上.随着入射波波幅的增大,分布于更高模态上的波能的比重增加,港内波能的分布趋于均匀,并且占有最大波能的共振模态逐渐由较低的模态向较高的模态转移.相比于波峰在前的等边N波,波谷在前的等边N波诱发的港内波能分布得更加均匀.