Sound Radiation Properties of Complex Modes in Rectangular Plates: A Numerical Study
Sound Radiation Properties of Complex Modes in Rectangular Plates: A Numerical Study
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DOI：
10.3813/aaa.918805
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发表时间：
2015
影响因子：
--
通讯作者：
Oliver Unruh;M. Sinapius;H. Monner
中科院分区：
文献类型：
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作者：
Oliver Unruh;M. Sinapius;H. Monner
实正模态的声辐射特性经常被用来表征声源，如振动板。通常假设结构阻尼均匀分布，因此本征模态是实模态。随着高性能复合材料结构应用的增加和对声舒适性的要求越来越高，约束层阻尼或嵌入弹性体层等阻尼处理可能会局部分布在振动结构的某些关键位置。这违背了结构阻尼均匀分布的假设，导致了复杂的模态振型。在这种情况下，共振内振动系统的动力学不再由纯驻波控制，而是由与行波的叠加控制。本文介绍了这种现象的声辐射特性的数值研究结果，这种现象通常被称为复振型。采用非均匀阻尼板的有限元模型，生成并研究了板的复杂振动模式。所生成的复模态的模态复杂度由模态共线性指数和驻波比的空间分布来表征。流体结构相互作用通过元素辐射方法实现，并用于根据远场辐射效率和声强空间分布对振动模式进行声学表征。结果表明，特征向量复杂度会严重影响结构模态的声辐射特性。
The sound radiation properties of real normal modes are often used to characterise acoustic sources such as vibrating plates. The assumption of homogeneously distributed structural damping is usually made and in consequence the eigenmodes are real. With the increasing use of high-performance composite structures and the demanding requirements for acoustic comfort, damping treatments such as constrained layer damping or embedded elastomer layers may be distributed locally at some critical locations of the vibrating structure. This violates the assumption of homogeneously distributed structural damping and results in complex mode shapes. In this case, dynamics of the vibrating systems within the resonances is no longer dominated by pure standing waves, but also by a superposition with travelling waves. This paper presents the results of a numerical study on sound radiation properties of this phenom-enon, generally known as complex modes of vibration. The finite element model of an inhomoge-neously damped plate is used to generate and investigate complex vibration patterns. The level of modal complexity of the generated complex modes is characterized by the modal collinearity index and the spatial distribution of the standing wave ratio. The fluid structure interaction is implemented by a elemental radiator approach and used for the acoustic characterisation of vibration patterns in terms of far-field radiation efficiencies and spatial distributions of sound intensity. It is shown that the eigenvector complexity can seriously affect the sound radiation properties of structural modes.