Submarine structural and acoustic attenuation
In this paper, the low frequency vibro acoustic responses from a submerged hull are attenuated using passive, active, and hybrid control strategies. An analytical model representing a simplified physical model of a submarine hull is developed, including the effects of ring stiffeners, bulkheads, and external fluid loading. At low frequencies, rotation of the propeller results in discrete tones at the blade passing frequency and its harmonics. The fluctuating forces at the propeller are transmitted through the propulsion system, resulting in excitation of the low frequency hull vibrational modes, which in turn results in a high level of structure borne radiated noise. In this work tuned vibration absorbers, active vibration control, and hybrid vibration absorbers are used to attenuate the breathing and bending modes of the submerged hull. The control performance of a hybrid vibration absorber is compared to the attenuation achieved using a passive absorber and the control performance of a fully active system. Results show that implementation of the hybrid vibration absorber results in significant attenuation of the structural and acoustic responses of the hull. The hybrid vibration absorber also requires a control force of lower magnitude compared with a fully active control system.