Acoustic and thermoacoustic properties of an additive manufactured lattice structure

With the advent of additive manufacturing, lattice structures can be printed with precisely controlled geometries. In this way, it is possible to realize porous samples with specific acoustic and thermoacoustic characteristics. However, to this aim and prior to the manufacturing process, it is fundamental to have a design tool that can predict the behaviour of the lattices. In the literature, Luu, Perrot, and Panneton [Acta Acust. United Ac. 103, 1050 (2017)] provide a model to characterize transport parameters of fibrous material with a certain fiber orientation with respect to the direction of wave propagation. In this work, finite element numerical simulations are used to improve their model in order to compute the thermoviscous functions of lattice structures composed of cylindrical struts arranged in Tetragonal Body Centred cells. New correlations for transport parameters are suggested, which are finally coupled with the semi-phenomenological model of Johnson-Champoux-Allard-Lafarge to obtain the complex density and bulk modulus of the equivalent fluid. These results are compared with the measurements carried out on two 3-dimensional-printed samples with hybrid impedance tube techniques.