Showing papers by "Gwenael Gabard published in 2020"
TL;DR: In this article, the acoustic behavior of 3D printed micro-lattices is investigated to assess the impact of defects induced by the Fused Deposition Modeling technique on the parameters of the equivalent fluid medium.
30 citations
TL;DR: In this paper, a folded metaporous surface optimized to achieve sub-wavelength and broadband perfect absorption is presented, which consists of four different helicoidal cavities filled by porous media, which are structured and quasi-isotropic micro-lattices with a variable lattice constant.
Abstract: This Letter reports a folded metaporous surface optimized to achieve sub-wavelength and broadband perfect absorption. Its unit cell is composed of four different helicoidal cavities filled by porous media, which are structured and quasi-isotropic micro-lattices with a variable lattice constant. The effective thickness and intrinsic losses of each helicoidal cavity can be adjusted independently by varying their macro- and micro-structures, namely, the number of revolution of the folded structure and the lattice constant of the micro-lattice. An analytical model predicting the physical properties of this metaporous surface is developed. The macro- and micro-structures are then jointly optimized for sub-wavelength broadband perfect absorption. Finally, the system is 3D printed and experimentally tested. The experimental results are found to be in good agreement with the theory and show an almost perfect absorption over a frequency range out of reach for the homogeneous constitutive porous medium and the only helicoidal cavities.
20 citations
TL;DR: A cavity shape is obtained leading to an almost perfect absorption for a frequency in the prescribed optimisation range using a model based on the Helmholtz equation and an adjoint-based method.
13 citations
TL;DR: This work presents a theoretical and numerical study of graded and anisotropic porous materials, for optimal broadband and angular absorption, and develops an optimization technique based on the simplex method that is relying on this database.
Abstract: The design of graded and anisotropic materials has been of significant interest, especially for sound absorption purposes. Together with the rise of additive manufacturing techniques, new possibilities are emerging from engineered porous micro-structures. In this work, we present a theoretical and numerical study of graded and anisotropic porous materials, for optimal broadband and angular absorption. Through a parametric study, the effective acoustic and geometric parameters of homogenized anisotropic unit cells constitute a database in which the optimal anisotropic and graded material will be searched for. We develop an optimization technique based on the simplex method that is relying on this database. The concepts of average absorption and diffuse field absorption coefficients are introduced and used to maximize angular acoustic absorption. Numerical results present the optimized absorption of the designed anisotropic and graded porous materials for different acoustic targets. The designed materials have anisotropic and graded effective properties, which enhance its sound absorption capabilities. While the anisotropy largely enhances the diffuse field absorbing when optimized at a single frequency, graded properties appear to be crucial for optimal broadband diffuse field absorption.
10 citations
TL;DR: A non-overlapping domain decomposition method is proposed to solve large-scale finite element models for the propagation of sound with a background mean flow and its benefit is demonstrated on a realistic turbofan engine intake configuration.
8 citations
13 Oct 2020
TL;DR: The field of aeroacoustics has gained much attention since the well-known acoustic analogies were first published in the 1950s as mentioned in this paper, and the continuous growth of computational resources has ena...
Abstract: The field of aeroacoustics has gained much attention since the well-known acoustic analogies were first published in the 1950s. In parallel, the continuous growth of computational resources has ena...
3 citations
TL;DR: In this paper, a general class of acoustic impedance conditions is considered where a linear dependence is assumed between the fluid velocity and the surface traction in addition to the classical impedance relating pressure and normal velocity, this generalised definition of the impedance includes effects such as the friction along the surface as well as coupling between the normal velocity and tangential force on the fluid.
2 citations
TL;DR: In this paper, two techniques to introduce source terms in the linearized Euler equations for the simulation of aeroacoustic propagation on a background mean flow are presented. But neither of these techniques is suitable for aero-acoustic applications.
Abstract: This paper presents two novel techniques to introduce source terms in the linearized Euler equations for the simulation of aeroacoustic propagation on a background mean flow. The first technique al...
1 citations