Kirby Ray
School of Engineering and Design, Mechanical Engineering, Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom.
J Acoust Soc Am. 2008 Oct;124(4):1930-40. doi: 10.1121/1.2967837.
Sound propagation in an acoustic waveguide is examined using a hybrid numerical technique. Here, the waveguide is assumed to be infinite in length with an arbitrary but uniform cross section. Placed centrally within the guide is a short component section with an irregular nonuniform shape. The hybrid method utilizes a wave based modal solution for a uniform section of the guide and, using either a mode matching or point collocation approach, matches this to a standard finite element based solution for the component section. Thus, one needs only to generate a transverse finite element mesh in uniform sections of the waveguide and this significantly reduces the number of degrees of freedom required. Moreover, utilizing a wave based solution removes the need to numerically enforce a nonreflecting boundary condition at infinity using a necessarily finite mesh, which is often encountered in studies that use only the standard finite element method. Accordingly, the component transmission loss may readily be computed and predictions are presented here for three examples: an expansion chamber, a converging-diverging duct, and a circular cylinder. Good agreement with analytic models is observed, and transmission loss predictions are also presented for multimode incident and transmitted sound fields.
使用一种混合数值技术研究声波在声学波导中的传播。在此，假设波导长度无限，具有任意但均匀的横截面。放置在波导中心的是一个短的组件部分，其形状不规则且不均匀。混合方法利用基于波的模态解来求解波导的均匀部分，并使用模式匹配或点配置方法，将其与基于标准有限元的组件部分解相匹配。因此，只需要在波导的均匀部分生成横向有限元网格，这显著减少了所需的自由度数量。此外，使用基于波的解消除了使用必然有限的网格在无穷远处数值强制非反射边界条件的需要，这在仅使用标准有限元方法的研究中经常遇到。因此，可以很容易地计算组件的传输损耗，这里给出了三个示例的预测结果：一个膨胀室、一个渐缩-渐扩管道和一个圆柱体。观察到与解析模型有很好的一致性，并且还给出了多模入射和透射声场的传输损耗预测。
