浅海内波影响下的波导不变量变化特性分析

针对浅海内波引起波导不变量变化的问题,利用声场波导不变量的概率分布并结合声场简正波的理论,研究了内波活动下波导不变量的时变性,给出了波导不变量变化的机理和规律.具体结论是,在负跃层波导中,声场的波导不变量的最大概率取值具有明显的频变特性.内波环境下,当声传播方向与内波波阵面平行时,接收声场简正波的幅度变化不大,但是简正波的相慢度差和群慢度差的变化却能引起波导不变量最大概率取值的变化;而当声传播方向与内波波阵面垂直时,内波引起的简正波耦合同样会导致波导不变量的最大概率取值的明显变化.

Time-varying characteristics of the waveguide invariant under internal wave condition in the shallow water area

To explain the change of the waveguide invariant β caused by the internal wave, the waveguide invariant is expressed as a stochastic distribution and the time-varying characteristics of β are analyzed; then the cause and principle of variation of β are discussed in terms of the normal modes theory of the acoustic field. It turns out that the waveguide invariant shows great frequency-dependent characteristics. And in the internal wave environment, when the sound is propagated parallel to the internal wave front, the sound field's composition of normal modes remains unchanged, but the turbulence in the group slowness and phase slowness of the main normal modes in the sound field may also change the distribution of β; when the sound is propagated perpendicular to the internal wave front, the coupling between acoustic normal modes might also cause obvious changes in the values of β.
Keywords： thermocline internal wave/tide sound field waveguide invaraiant