Finite Element Calculation And Analysis For Rotationally Asymmetric Sound Absorbent Structure

The finite element analysis for sound absorbent structures with rotational symmetry has been fully developed, with results being in accordance with experimental data. However, symmetry model could approximate the case that the unit cross section of absorbent material is hexagonal. In order to approach practical situation and to provide more possibility for sound absorbent structure choice, finite element models are build for several rotationally asymmetric sound absorbent structures, and numerical simulations have been conducted. The detailed works are as follows:1. Realization of numerical simulation for rotationally asymmetric sound absorbent structures by finite element method (FEM). Some problems involved in acoustic calculation, such as absorbent boundary, loss factor and structure-acoustics interface, are properly resolved. The criterion for element size choice is recommended by comparing FEM result with analytical result.2. The influence on absorption coefficient brought from shape choice with cylindrical or cone-shaped cavity, square or hexagonal profile, from different closure as air or water, from different material properties and structure sizes, are analyzed based on the numerical calculations. Some general characteristics are summarized. It shows that lowest resonance frequency of sound absorbent coefficient is inversely proportional to volume of cavity and sound absorbent coefficient is proportional to perforated percentage. In the whole considered frequency range, the acoustical performance of rotationally asymmetric structures is better than that of symmetric structures.