圆孔非线性声阻抗三维时域仿真与特性分析

为研究有限振幅声波作用下圆孔的非线性声学特性,提出了基于三维时域计算流体动力学(CFD)仿真的圆孔非线性声阻抗提取方法,通过求解层流方程来模拟声信号在圆孔及上下游的传播,以及采用横向周期性边界条件来考虑高穿孔率时圆孔之间相互作用的影响。研究了不同幅值声波作用下孔径、厚度和穿孔率对声阻抗的影响规律,通过对质点振速幅值、频率和板厚等组成的无量纲参量进行非线性回归分析,得到了圆孔非线性声阻抗的拟合公式,并将其转换为可考虑多频声波影响的时域模型。最后结合声阻抗时域模型和有限差分方法计算了直通穿孔管消声器在小振幅和有限振幅声波作用下的传递损失,通过与实验测量结果的比较,验证了拟合公式的准确性和实用性。

Three-dimensional time-domain simulation and characteristic analysis of the nonlinear acoustic impedance of circular orifice

In order to study the nonlinear acoustic characteristics of circular orifice under finite amplitude acoustic wave excitation, a method based on three-dimensional time-domain computational fluid dynamics (CFD) simulation is proposed to determine the nonlinear acoustic impedance of circular orifice. By solving laminar flow equations, the propagation of acoustic signal in circular orifice, upstream and downstream is simulated, and the effect of interaction between circular orifices with large porosity is considered by using lateral periodic boundary condition. The effects of diameter, thickness and porosity on acoustic impedance under different sound amplitudes are studied. By using nonlinear regression analysis of the dimensionless parameters composed of particle velocity amplitude, frequency, thickness, etc., the fitting formula of nonlinear acoustic impedance of circular orifice is obtained and transformed into the time domain model which can take into account the influence of multi-frequency acoustic waves. Finally, the transmission losses of straight through perforated tube silencer under low and finite amplitude acoustic waves are calculated by using the time-domain acoustic impedance model and the finite difference method. By comparing with experimental measurement results, the accuracy and practicability of the fitting formula are validated.