Characteristics of flow-induced vibration and self-noise of locally resonant composite sandwich beam acoustic window

Abstract The present study focuses on the control of sonar hydrodynamic self-noise, considering the coupled vibration of acoustic windows with internal/external acoustic fields and turbulent boundary layer excitation. A hybrid numerical method is employed to establish a computational model for hydrodynamic self-noise analysis. Numerical simulations are conducted to evaluate the noise reduction characteristics of composite sandwich beams with locally resonant composite sandwich beam acoustic window. The analysis reveals that the periodic local resonator units in the composite sandwich beam create enriched vibrational modes, functioning as equivalent dynamic dampers by storing vibrational energy. This effectively suppresses bending wave propagation within band gaps. Additionally, the higher-order modal wavenumber spectra of the composite beam structure exhibit reduced peaks, thereby weakening the interaction between low-wavenumber components of turbulent boundary layer pressure fluctuations and structural modal wavenumber spectra. This also reduces modal acoustic-structural coupling between the structure and internal acoustic field, leading to significant attenuation of cavity-contained hydrodynamic self-noise. Through optimal parameter design of the resonator units, the proposed optimized locally resonant composite sandwich beam acoustic window achieves a 16 dB reduction and 33 dB reduction, respectively, compared to sandwich and uniform plates in the 245-1000 Hz frequency band for cavity hydrodynamic self-noise spectral level.