In the linear regime and in the absence of mean flow, the impedance of perforated liners is driven by visco-thermal effects. In this paper, two numerical models are employed for predicting these visco-thermal losses. The first model is the linearized compressible Navier–Stokes equations (LNSE), solved in the frequency domain. The second model is the Helmholtz equation with a visco-thermal boundary condition, accounting for the influence of the acoustic boundary layers. These models are compared and validated against measurements. The quantitative analysis of the dissipation rate due to viscosity, computed from the LNSE solutions of four perforated plates, highlights significant differences between the edge effects of a macro- and a micro-perforated plate. In the latter case, a jet is present at the entrances of the perforation. In contrast, the proposed numerical method to calculate the impedance of perforated liners, based on the Helmholtz equation and a visco-thermal boundary condition, is found to be computationally cheaper and to provide reliable predictions.

中文翻译：

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多孔板衬板的数值模拟：粘热耗散机理分析

在线性条件下，在没有平均流量的情况下，多孔衬管的阻抗是由粘热效应驱动的。在本文中，使用两个数值模型来预测这些粘热损失。第一个模型是在频域中求解的线性可压缩Navier–Stokes方程（LNSE）。第二个模型是具有粘热边界条件的亥姆霍兹方程，它考虑了声边界层的影响。将这些模型进行比较，并根据测量结果进行验证。由四块多孔板的LNSE溶液计算得出的由于粘度引起的耗散率的定量分析显示出，大孔板和微孔板的边缘效应之间存在显着差异。在后一种情况下，在射孔的入口处存在射流。相反，