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中文核心期刊

非对称耦合条件下冰层导波的泄漏衰减特性

Leakage attenuation characteristics of guided waves in asymmetrically coupled ice sheets

  • 摘要: 基于弹性波理论推导了气–冰–水非对称耦合条件下的海冰中冰层导波的频散方程, 对典型冰声参数下的冰层导波频散方程进行了求解, 构建了冰层导波传播的二维有限元仿真模型。通过理论计算与有限元仿真, 探究了海冰中冰层导波的泄漏衰减特性, 讨论了影响冰层导波泄漏衰减大小的因素。研究结果表明: 海冰中绝大部分冰层导波的相速度值越接近纵波波速、横波波速和表面波波速时, 导波的能量越集中于冰层内部和气–冰界面处, 不易向水中泄漏能量, 其泄漏衰减系数值越小; 低阶模态冰层导波实波数曲线发生的弯曲、替换、偏移和分离等变化与导波的泄漏衰减有关; 冰层导波的泄漏衰减使得冰层导波的传播振幅随传播距离增加呈指数级减小, 只有泄漏衰减系数较小或等于0的导波可在冰层中远距离传播; 冰层导波的泄漏衰减系数在相同频厚积(频率与厚度的乘积)处与冰层厚度成反比; 冰层导波在冰–水界面处的法向位移越大, 冰层导波的泄漏衰减系数越大。

     

    Abstract: Based on elastic wave theory, the dispersion equation of ice-guided waves in sea ice under asymmetric air-ice-water coupling conditions is derived. The dispersion characteristics are solved for typical ice-acoustic parameters, and a two-dimensional finite element model is established to simulate ice-guided wave propagation. Through theoretical calculations and finite element simulations, the leakage attenuation characteristics of ice-guided waves in sea ice are investigated, and the factors influencing leakage attenuation are analyzed. The results indicate that when the phase velocity of most ice-guided waves approaches the longitudinal wavespeed, transverse wavespeed, or surface wavespeed in sea ice, the wave energy becomes more concentrated within the ice layer and at the air-ice interface, reducing energy leakage into the water and resulting in lower leakage attenuation coefficients. The bending, replacement, shifting, and separation of the real wavenumber curves for low-order ice-guided wave modes are related to leakage attenuation. Leakage attenuation causes the wave amplitude to decay exponentially with propagation distance, and only waves with negligible or zero leakage attenuation can propagate over long distances in sea ice. Additionally, the leakage attenuation coefficient at a given frequency-thickness product is inversely proportional to ice thickness. Furthermore, a larger normal displacement at the ice-water interface leads to a higher leakage attenuation coefficient for ice-guided waves.

     

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