Annular acoustic black holes to reduce sound radiation from cylindrical shells

Annular acoustic black holes (ABHs) have been recently proposed as a potential means for reducing vibrations of cylindrical shells. The latter are very common structures in the naval, aeronautic and industrial sectors so widening ABH applications from flat plates to curved seems worth exploring. This work focuses on benefits embedding annular indentations shells reduce outward sound radiation. goal paper is propose semi-analytical method determine power, radiation efficiency, source location far-field pressure compare them with those uniform thickness vibration field computed by Gaussian expansion (GEM) within Rayleigh–Ritz approach. Then, radiated obtained solving Helmholtz equation coordinates using Green’s function method. surface cylinder discretized into small finite size radiators an impedance matrix used obtain terms shell radial velocity. To regions responsible far sound, use made supersonic intensity (SSI). A calculate SSI spatial domain which allows one make direct previously velocity distributions. whole methodology validated against element (FEM) simulations after that, results presented acoustically thick shell. roles played critical ring frequencies reported spectra efficiency get analysed. It shown that can become effective when flexural motion dominates over circumferential one. slow down bending waves inside makes structural (in relation speed) subsonic at some point, clearly diminishes efficiency. Overall, it described why strongly help far-field.