Extension of fictitious domain methods for vibroacoustic problems – Analysis of heterogeneous, foamed damping materials

振动声学问题虚拟域方法的扩展 â 分析异质泡沫阻尼材料

• 批准号: 503865803
• 负责人: Professor Dr.-Ing. Alexander Düster
• 金额: --
• 依托单位: Institut für Mechanik (IFME)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/503865803?language=en
• 关键词: Extension; fictitious; domain; methods; vibroacoustic

Even today, the prediction of the acoustical behaviour of components made of materials exhibiting a highly heterogeneous microstructure is a very demanding and challenging task. There are several reasons that make this problem so difficult to solve. On the one hand, the microstructure can only be accurately resolved if a large number of finite elements are deployed. On the other hand, all physically relevant interactions between the structural and fluid domain need to be taken into account. As mentioned before the body-fitted discretization of highly complex structures demands a large number of finite elements (degrees of freedom) and thus results in inacceptable computational times. Consequently, alternative methods, such as fictitious domain approaches, are required. Over the last years fictitious domain methods, such as the finite cell method (FCM), have proven their capabilities. To account for the vibroacoustic properties of microstructured materials these methods need to be extended. Therefore, the acoustic wave equation in the time domain or the Helmholtz equation in the frequency domain need to discretized by means of the FCM. Moreover, suitable coupling strategies that result in a weak or strong coupling need to be devised. Here, the main advantage of fictitious domain methods is the ability to take complex geometrical features into account while being able to straightforwardly superimpose cells with mechanical and fluidic properties. Thus, an efficient and robust strategy for vibroacoustic problems can be set up. Despite the application of nonconforming discretizations the numerical effort is still considerably large. Therefore, a second idea uses simplified numerical models based on homogenization techniques. To this end, the structure is assumed to consist of a homogeneous medium where the microstructure is neglected. In spite of this model simplification it is still expected to achieve reasonable results for specific applications. Besides the development of numerical methods a second focus is put on a comprehensive validation procedure. In this context, different experimental set-ups are deployed. To check the vibrational behavior of the structure under investigation a 3D laserscanning- vibrometer is used. In addition, the frequency-dependent acoustic parameters are measured by means of simple experimental set-ups such as an impedance tube and the results are compared to the numerically obtained values. As a last step the sound pressure radiation is tested in an anechoic room using microphone arrays and far field microphones. The acquired data are the foundation for illustrating the performance of the proposed methods.

即使在今天，预测由具有高度非均匀微观结构的材料制成的部件的声学行为也是一项非常苛刻和具有挑战性的任务。有几个原因使得这个问题如此难以解决。一方面，只有部署大量有限元，才能准确解析微观结构。另一方面，需要考虑结构域和流体域之间所有物理相关的相互作用。如前所述，高度复杂结构的拟体离散化需要大量的有限元（自由度），从而导致计算时间不可接受。因此，需要替代方法，例如虚拟领域方法。在过去的几年里，虚拟域方法，如有限单元法（FCM），已经证明了它们的能力。为了解释微结构材料的振动声学特性，这些方法需要扩展。因此，声波方程在时域或亥姆霍兹方程在频域需要用FCM进行离散化。此外，需要设计导致弱耦合或强耦合的合适耦合策略。在这里，虚拟域方法的主要优点是能够考虑复杂的几何特征，同时能够直接叠加具有机械和流体特性的细胞。因此，可以建立一种有效而稳健的振动声学问题处理策略。尽管应用了非一致性离散化，但数值计算的工作量仍然相当大。因此，第二种方法是使用基于均质化技术的简化数值模型。为此，假设结构由均匀介质组成，忽略微观结构。尽管这种模型简化了，但对于特定的应用仍然期望得到合理的结果。除了数值方法的发展，第二个重点放在一个全面的验证程序。在这种情况下，部署了不同的实验装置。为了检测所研究结构的振动特性，采用了三维激光扫描测振仪。此外，通过阻抗管等简单的实验装置测量了频率相关的声学参数，并将结果与数值计算结果进行了比较。作为最后一步，声压辐射在消声室使用麦克风阵列和远场麦克风进行测试。所获得的数据是说明所提方法性能的基础。