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.