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中文核心期刊

北极冰-水耦合系统中声波传播特性

Propagation of acoustic waves in a coupled ice-water system for the Arctic Ocean

  • 摘要: 利用固体和流体介质中波传播理论,导出了冰-水两层复合结构中导波频散方程。进一步,利用二分法对频散方程进行了数值求解,得到了ω-k频散曲线(ωk分别为圆频率和波数),以及相速度和群速度频散曲线。结果表明:冰-水两层复合结构中导波由具有相同厚度水层和冰层中导波耦合而成,但与水层和冰层中导波频散曲线相比,复合结构中导波频散曲线除第1阶模式外,其余高阶模式均发生了很大变化。从原水层第1阶模式的截止频率开始,复合结构第2阶模式的相速度曲线被压低,各高阶(大于2阶)模式的相速度曲线出现一个跃变点,群速度曲线出现一个极大和一个极小值。水层越厚,复合结构各高阶模式的截止频率越低,相同频带内导波模式越丰富。水层厚度保持不变时,复合结构各阶模式的相速度和群速度曲线均随冰层厚度的增加而向低频方向移动。另外,还进一步分析了冰-水复合结构的导波波结构,发现第1阶导波模式的能量主要集中在冰层内和海表面附近,而2阶以上高阶导波模式的振动位移幅度随深度方向呈现周期性特征,并且模式阶数越高,振动越复杂。

     

    Abstract: Propagation of acoustic waves in a coupled ice-water system for the Arctic Ocean is studied.The sea ice is seen as homogeneous as well as the water.The dispersion equation is derived by using the theory of waves in solid and liquid media.The ω-k dispersion curves are obtained by solving the dispersion equation using the bisection method,from which the phase and the group velocity dispersion curves are obtained.Numerical results show that the dispersion curves corresponding to the waves in the coupled ice-water system arise from the coupling of those corresponding to the waves in an ice layer and a water layer.The phase velocity dispersion curve corresponding to the m-th(m> 1) guided wave in the coupled ice-water system is formed from that corresponding to the second order wave in the ice layer and that corresponding to the m-th(m ≥ 1) guided waves in the water layer.Moreover,the group velocity dispersion curve corresponding to the m-th(m> 1) order guided wave has a maximum value and a minimum value.In addition,the wave structure of guided waves in the coupled ice-water system is analyzed in detail.Results show that the energy corresponding to the first order guided wave is concentrated in the ice layer and the water near the ice.The distribution of radial and axial displacement amplitude,which is corresponding to the m-th(m ≥ 2) order guided wave,along the depth direction is periodic.Moreover,the higher the order,the more complex the vibration.

     

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