Investigation of noise reduction features in bladder-type attenuators for underwater vehicle drainage systems

The drainage system is a critical component in the normal operation of underwater vehicles, where reducing flow pressure pulsations and noise is essential for improving stability, reliability, and stealth performance. This study aims to investigate the suppressive effect of a bladder-type attenuator on pipeline noise through the reduction of system flow pressure pulsations. A system simulation model was established to explore this issue by combining computational fluid dynamics (CFD)-based analysis of unsteady flow fields with LightHill's acoustic analogy and an acoustic–solid coupling method, investigating the influence of a bladder-type attenuator on flow pressure pulsations and noise characteristics in auxiliary pipelines. Experiments were also conducted to capture pressure pulsations and noise data. The comparison demonstrated that numerical predictions were consistent with measured results. Findings revealed that the dominant noise in the auxiliary pipeline primarily originated from vibrations of pipe walls, producing radiation noise, while velocity-induced flow noise appeared mainly in the low-frequency spectrum. Incorporating a bladder-type attenuator was shown to effectively suppress both pressure pulsations and associated noise in the auxiliary piping system.