Numerical Assessment of Convective PGMs

Acoustic metamaterials enable advanced wavefront control, offering compact and lightweight solutions for noise reduction in aeronautical applications. As thin metasurface, they can be integrated onto existing structures, like nacelle intakes or control surfaces, to absorb or redirect acoustic energy. However, performance degrades in the presence of a background flow due to the change in the mechanism of propagation of the acoustic perturbation. To address this, a spacetime-based analytical framework incorporates flow effects in the medium design by introducing spacetime coordinate transformations. The mathematical tools of differential geometry extend the applicability of static designs to convective environments. This study evaluates the performance of a convective phase gradient metasurface based on a space-coiled, 8-unit cell design, optimised for frequency robustness. Numerical solutions obtained in the frequency domain aim to assess the capability of a flow-corrected design in maintaining wave deflection under grazing flow.