A numerical investigation of Helmholtz resonators in the presence of grazing flow by means of the lattice Boltzmann method Free

Helmholtz resonators remain widely used in noise control. In applications such as aircraft engines and exhaust systems, the presence of a grazing flow significantly changes their behavior, and a correct prediction of their acoustic properties is essential to improve noise reduction. With the purpose of understanding the physical phenomena associated with the acoustic-flow interaction, the simulation of a single 2D Helmholtz resonator was considered by means of an in-house numerical code based on the lattice Boltzmann method (LBM). The results have been validated against published data based on both experimental results and direct numerical simulation (DNS) for normally incident acoustic waves in the absence of flow. The investigations will proceed by taking into account grazing acoustic waves in the presence of a grazing flow, similarly to the conditions found in a liner test rig. Efforts will be focused on typical aircraft engine inlet conditions, i.e., high Mach numbers and SPL. Both experimental and numerical results will be compared in terms of absorption coefficient and impedance.