To broaden its’ effective frequency range and to improve its transmission loss performance, a modified design of a Helmholtz resonator is proposed and evaluated by implementing a rigid baffle in its cavity. Comparison is then made between the proposed design and the conventional one by considering a rectangular duct with the resonator implemented in the presence of a mean grazing flow. For this, a linearized 2D Navier-Stokes model in frequency domain is developed. After validated by benchmarking with the available experimental data and our experimental measurements, the model is used to evaluate the effects of (1) the width of the rigid baffle, (2) its implementation location/height , (3) its implementation configurations (i.e., attached to the left sidewall or right sidewall), (4) the grazing mean flow (Mach number), and (5) the neck shape on a noise damping effect. It is shown that as the rigid baffle is attached in the 2 different configurations, the resonant frequencies and the maximum transmission losses cannot be predicted by using the classical theoretical formulation , especially as the grazing Mach number is greater than 0.07, i.e., . In addition, there is an optimum grazing flow Mach number corresponding to the maximum transmission loss peak, as the width is less than half of the cavity width , i.e., . As the rigid plate width is increased to , one additional transmission loss peak at approximately 400 Hz is produced. The generation of the 12 dB transmission loss peak at 400 Hz is shown to attribute to the sound and structure interaction. Finally, varying the neck shape from the conventional one to an arc one leads to the dominant resonant frequency being increased by approximately 20% and so the secondary transmission loss peak by 2-5 dB. The present work proposes and systematically studies an improved design of a Helmholtz resonator with an additional transmission loss peak at a high frequency, besides the dominant peak at a low frequency.

中文翻译：

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掠流作用下带有刚性挡板的亥姆霍兹谐振器的空气声衰减性能

为了拓宽其有效频率范围并改善其传输损耗性能，提出了一种亥姆霍兹谐振器的改进设计，并通过在其空腔中安装刚性挡板来进行评估。然后，通过考虑在平均掠流情况下实现谐振器的矩形管道，对建议的设计与传统设计进行比较。为此，开发了频域的线性化二维Navier-Stokes模型。经过对可用实验数据和我们的实验测量结果进行基准测试验证后，该模型可用于评估以下因素的影响：（1）刚性挡板的宽度，（2）其实现位置/高度，（3）其实施配置（即，连接到左侧壁或右侧壁），（4）掠射平均流量（马赫数）和（5）颈部形状，具有降噪效果。结果表明，由于刚性挡板以两种不同的结构连接，因此无法使用经典的理论公式来预测共振频率和最大传输损耗，尤其是当放牧马赫数大于0.07时，即。此外，存在一个最佳的放牧流动马赫对应于最大传输损耗峰值数，为宽度小于一半的腔宽度的，即。随着刚性板的宽度增加到，在大约400 Hz处产生一个额外的传输损耗峰值。显示了在400 Hz处产生12 dB传输损耗峰值的原因是声音和结构的相互作用。最后，将颈部的形状从传统的形状改变为弧形形状会导致主要的谐振频率增加大约20％，因此次级传输损耗峰值增加2-5 dB。本工作提出并系统地研究了亥姆霍兹谐振器的改进设计，该亥姆霍兹谐振器除了具有低频的主峰外，还具有高频的附加传输损耗峰。