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首页> 外文会议>IUTAM Symposium on Diffraction and Scattering in Fluid Mechanics and Elasticity >Ultrasonic backscattering enhancements for truncated objects in water: quantitative models, tests and special cases
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Ultrasonic backscattering enhancements for truncated objects in water: quantitative models, tests and special cases

机译：超声波反向散射增强在水中截短物体的增强功能：定量模型，测试和特殊情况

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This survey is concerned with the scattering of sound in water by objects whose size significantly exceeds the acoustic wavelength. Diffraction from the edges of the object can be important for regions where reflected contributions are weak. Elastic contributions to the scattering, however, can be much larger in magnitude for certain viewing angles than simple edge diffraction. Such elastic contributions can greatly enhance the visibility of truncated cylinders imaged with a sonar [1]. For situations where the dominant elastic contributions are the result of leaky waves excited on truncated objects, an approximation method has been developed [2, 3]. Leaky waves have phase velocities that exceed the speed of sound in water. Examples include Rayleigh waves on metallic objects, the symmetric generalization of Lamb waves on plates and shells, and (at sufficiently high frequencies) the lowest antisymmetric generalization of a Lamb wave. This type of scattering enhancement, has been measured by us for metallic tilted bluntly truncated cylinders [4, 5, 6] and cubes [7] and glass disks. For most of these examples, the leaky wave is significantly attenuated upon traveling the length of the scaterer. As a consequence of that damping, the quality factor Q is small for the global modes associated with the reverberations of the leaky waves between truncations on the object. Consequently resonances associated with the global modes of the scatterer can be unimportant in the case of shells, the leaky Lamb waves are sufficiently dispersive that frequency-dependent synchronization conditions must be met to facilitate strong coupling between the leaky waves and the incident acoustic field [4].
机译：该调查涉及其尺寸明显超过声波长的物体在水中的散射。来自物体边缘的衍射对于反射贡献较弱的区域可能是重要的。然而，对于某些观察角度而言，对于特定的边缘衍射，幅度的弹性贡献可以大得多。这种弹性贡献可以大大提高与声纳成像的截短圆柱体的可见性[1]。对于主导弹性贡献的情况是在截短的物体上激发泄漏波的结果，已经开发了一种近似方法[2,3]。泄漏的波具有超过水中声速的相速度。实例包括在金属物体上的瑞利波，板在板材和壳体上的羊光波的对称广义，（足够高的频率）羔羊波的最低反对称推广。这种类型的散射增强已经通过我们测量金属倾斜的钝截圆柱[4,5,6]和立方体[7]和玻璃盘。对于大多数这些示例，泄漏波在行驶煤机的长度时显着减弱。由于该阻尼，质量因子Q小于与对象上截断之间的泄漏波的混响相关联的全局模式。因此，在壳体的情况下，与散射体的全局模式相关联的共振可以是不重要的，泄漏的羔羊波足以充分分散，必须满足频率相关的同步条件，以便于泄漏波和入射声场之间的强耦合[4 ]。

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