Numerical Modeling of Internal Helmholtz Resonators Created by Punching Small Holes on a Thin-Walled Tube 2019-01-1486
Helmholtz resonators are normally an afterthought in the design of mufflers to target a very specific low frequency, usually the fundamental firing frequency of the engine. Due to space limitations in a complex muffler design, a resonator may have to be built by punching a few small holes on a thin-walled tube to create a neck passage into a small, enclosed volume outside the tube. The short neck passage created by punching a few small holes on a thin-walled tube can pose a great challenge in numerical modeling, especially when the boundary element method (BEM) is used. In this paper, a few different BEM modeling approaches are compared to one another. These include modeling both sides of the thin-walled tube and the details of each small hole, modeling just the mid surface of the thin-walled tube but with the holes and possibly an added neck length, and modeling an equivalent perforated surface patch on the tube without any holes. The BEM results are compared to a detailed simulation using the finite element method (FEM). In the end, an optimal and reliable approach is suggested, especially when the Helmholtz resonator is only a small portion in a complex muffler design. Results are also compared to the 1D analytical solution using proper end corrections.
Hao Zhou, T. W. Wu
Univ. of Kentucky
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