Hirosawa Kunikazu, Nakagawa Hiroshi
Acoustic Solution Division, Nihon Onkyo Engineering Co., Ltd., Sumida-ku, Tokyo, 130-0021, Japan.
J Acoust Soc Am. 2017 Jun;141(6):4301. doi: 10.1121/1.4984291.
Formulae to predict non-acoustical parameters (i.e., flow resistivity, tortuosity, and viscous and thermal characteristic lengths) of deformed fibrous porous materials are proposed provided that the original values of these parameters are known in advance. These formulae are developed using numerical fluid analyses. The flow resistivity was calculated by using the finite element method for a two-dimensional incompressible viscous fluid approximated by Oseen flow. The tortuosity and characteristic lengths were calculated by using the complex variable boundary element method for a two-dimensional potential flow. These calculations showed that the flow resistivity was inversely proportional to the porosity multiplied by the three-halves power of the compression ratio, that the tortuosity can be represented by a linear expression of the porosity, and that both characteristic lengths changed in the same manner with respect to the porosity. These tendencies agreed well with measurements of real glass wools of various bulk densities. The proposed prediction formulae for the parameters were then derived from the tendencies obtained from the numerical analyses. The predicted parameter values were compared with the calculated parameters and good agreement was obtained, confirming the validity of the proposed formulae.
提出了用于预测变形纤维多孔材料非声学参数（即流阻、曲折度以及粘性和热特征长度）的公式，前提是这些参数的原始值是预先已知的。这些公式是通过数值流体分析得出的。流阻是通过有限元方法对由奥森流近似的二维不可压缩粘性流体进行计算得到的。曲折度和特征长度是通过复变边界元方法对二维势流进行计算得到的。这些计算表明，流阻与孔隙率乘以压缩比的二分之三次方成反比，曲折度可以用孔隙率的线性表达式表示，并且两个特征长度相对于孔隙率的变化方式相同。这些趋势与各种堆积密度的实际玻璃棉的测量结果吻合良好。然后根据数值分析得到的趋势推导出了所提出的参数预测公式。将预测的参数值与计算得到的参数进行比较，得到了良好的一致性，证实了所提出公式的有效性。
