title: Design of broadband time-domain impedance boundary conditions using the oscillatory-diffusive representation of acoustical models.
abstract: A methodology to design broadband time-domain impedance boundary conditions (TDIBCs) from the analysis of acoustical models is presented. The derived TDIBCs are recast exclusively as first-order differential equations, well-suited for high-order numerical simulations. Broadband approximations are yielded from an elementary linear least squares optimization that is, for most models, independent of the absorbing material geometry. This methodology relies on a mathematical technique referred to as the oscillatory-diffusive (or poles and cuts) representation, and is applied to a wide range of acoustical models, drawn from duct acoustics and outdoor sound propagation, which covers perforates, semi-infinite ground layers, as well as cavities filled with a porous medium. It is shown that each of these impedance models leads to a different TDIBC. Comparison with existing numerical models, such as multi-pole or extended Helmholtz resonator, provides insights into their suitability. Additionally, the broadly-applicable fractional polynomial impedance models are analyzed using fractional calculus.
authors.affiliation: ONERA-The French Aerospace Lab, 31055 Toulouse, France.
authors.forename: Florian
authors.initials: F
authors.lastname: Monteghetti
authors.affiliation: ISAE-SUPAERO, Université de Toulouse, 31055 Toulouse, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Matignon
authors.affiliation: ONERA-The French Aerospace Lab, 31055 Toulouse, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Piot
authors.affiliation: ONERA-The French Aerospace Lab, 31055 Toulouse, France.
authors.forename: Lucas
authors.initials: L
authors.lastname: Pascal