Surface homogenization of an array of Helmholtz resonators for a viscoacoustic model using two-scale convergence

Abstract

We derive the weak limit of a linear viscoacoustic model in an acoustic liner that is a chamber connected to a periodic repetition of elongated chambers -the Helmholtz resonators. As model we consider the time-harmonic and linearized compressible Navier-Stokes equations for the acoustic velocity and pressure. Following the approach in Schmidt et al., J. Math. Ind 8:15, 2018 for the viscoacoustic transmission problem of multiperforated plates the viscosity is scaled as δ 4 with the period δ of the array of chambers and the size of the necks as well as the wall thickness like δ 2 such that the viscous boundary layers are of the order of the size of the necks. Applying the method of two-scale convergence we obtain with a stability assumption in the limit δ → 0 that the acoustic pressure fulfills the Helmholz equation with impedance boundary conditions. These boundary conditions depend on the frequency, the length of the resonators and through the effective Rayleigh conductivity -that can be computed numerically -on the shape of their necks. We compare the limit model to semi-analytical models in the literature.