Numerical Assessment of Convective PGMs
Giada COLOMBO, Umberto IEMMA
Abstract. 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.
Keywords
Metamaterials, Acoustic Metacontinuum, Spacetime, Metasurfaces, Convective Metasurfaces
Published online 7/20/2026, 6 pages
Copyright © 2026 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Giada COLOMBO, Umberto IEMMA, Numerical Assessment of Convective PGMs, Materials Research Proceedings, Vol. 69, pp 54-59, 2026
DOI: https://doi.org/10.21741/9781644904251-10
The article was published as article 10 of the book CEAS – AIDAA Conference 2025
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
References
[1] T. J. Cui, D. R. Smith, and R, Liu, Metamaterials – Introduction to metamaterials. Boston, Ma: Springer US, 2010.
[2] G. Palma, , H. Mao, L. Burghignoli, P. Göransson and U. Iemma, Acoustic metamaterials in aeronautics, Applied Science, 8 (2018), 971-989. https://doi.org/10.3390/app8060971
[3] G. Palma, and L. Burghignoli, On the integration of acoustic phase-gradient metasurfaces in aeronautics, International Journal of Aeroacoustics, 19 (2020) 294-310. https://doi.org/10.1177/1475472X20954404
[4] P. Cobo, H. Ruiz, A. Julian, Double-Layer Microperforated Panel/Porous Absorber as Liner for Anechoic Closing of the Test Section in Wind Tunnels, AAuA, 96 (2010), 914-922. https://doi.org/10.3813/AAA.918350
[5] G. Palma, L. Burghignoli and U. Iemma, A framework for micro-perforated absorbers optimization, Proc. 29th Int. Congr. Sound Vibr., Prague, Czech Republic : ICSV (2023).
[6] K. Hyunsu and S. Ahmet, Acoustic performance of Helmholtz resonator with flow, JVNV, 7 (2011), 285-305. https://doi.org/10.1504/IJVNV.2011.043191
[7] M. Li, H. J. Wu, and Y. X. Yuan, Metasurface zero-impedance matching mechanism for aerodynamic noise reduction, JSV, 536 (2022), 117147- 117161. https://doi.org/10.1016/j.jsv.2022.117147
[8] Y. He, Z. Siyang and X. Huang, Extensions to the acoustic scattering analysis for cloaks in non-uniform mean flows, JASA, 146 (2019), 41-49. https://doi.org/10.1121/1.5115046
[9] H. Ryoo and W. Jeon, Effect of compressibility and non-uniformity in flow on the scattering pattern of acoustic cloak. Sci. Rep., 7 (2017), 2125- 2136. https://doi.org/ 10.1038/s41598-017-02143-y
[10] U. Iemma, Theoretical and numerical modelling of acoustic metamaterials for aeroacoustic applications, Aerospace, 3 (2016), 15-34. https://doi.org/10.3390/aerospace3020015
[11] U. Iemma, and G. Palma, Design of metacontinua in the aeroacoustic spacetime, Scientific Reports, 10 (2020), 18192- 18202. https://doi.org/10.1038/s41598-020-74304-5
[12] A. N. Norris, Acoustic cloaking theory, R. Soc. A : Math. Phys. Eng. Sci., 464 (2008), 2411-2434. https://doi.org/10.1098/rspa.2008.0076
[13] C. García-Meca, S. Carloni, C. Barceló, G. Jannes, J. Sánchez-Dehesa, and A. Martínez, Analogue Transformation in Physics and their Application to Acoustics, Sci. Rep., 3 (2013), 2009-2014. https://doi.org/10.1038/srep02009
[14] M. Visser, Acoustic propagation in fluids: an unexpected example of Lorentzian geometry, (1993), 1-11. https://doi.org/10.48550/arXiv.gr-qc/9311028
[15] G. Colombo, G. Palma and U. Iemma, Numerical Aeroacoustic Assessment of a Metacontinuum Device Impinged by a Laser-Generated Sound Source, J. Eng., (2024), 1-11. https://doi.org/10.1155/2024/5421663
[16] G. Colombo and U. Iemma, Assessment of the performances and limitations of spacetime convective corrections for acoustic metacontinua design, Sci. Rep, 15 (2025), 7827 -7839. https://doi.org/10.1038/s41598-025-92264-6
[17] G. Palma, I. Cioffi, F. Centracchio, L. Burghignoli, and U. Iemma, Steering of Acoustic Reflection from Metasurfaces through Numerical Optimization, Proc. 25th AIAA/CEAS Aeroacoustic Conf., Delft, The Netherlands: The American Inst. of Aeroacoustics and Aeronautics, (2019), 1-10
[18] G. Palma and U. Iemma, A metacontinuum model for phase gradient metasurfaces. Sci. Rep., 13 (2023), 13038 – 13049. https://doi.org/10.1038/s41598-023-39956-z
