NUMERICAL PREDICTION OF PERFORATED TUBE ACOUSTIC IMPEDANCE

The use of perforated sheets is very common in noise control applications such as mufflers, aero - engines, building acoustics and heating ventilation and air - conditioning systems. The acoustic performance of these liners is expressed mathematically in terms of its impedance. Th ere is a great amount of literature available to estimate the liner impedance. Most of the models are semi - empirical in nature and derived from experimental studies. Geometric parameters like orifice diameter, plate thickness, cross - sectional dimension, ho le distribution pattern, operating flow conditions and sound pressure levels play a critical role in perforated tube impedance estimations. In this work, a numerical methodology was developed based on Finite - Element Methods, to estimate the impedance of pe rforated plate and validated with existing literature results for stationary flow conditions. Perforated plate inside the circular tube is considered as a computational acoustic domain. Plane wave excitation is applied as the inlet boundary condition at on e end of the tube , anechoic termination is applied as the outlet boundary condition and the rest of the e xterior domain is assumed to be acoustically rigid. This methodology has been extended to evaluate the impedance of perforated tubes. Parametric studies are conducted to study the curvature effect of perforated tubes on impedance, by changing the tube diameter.