Yan Tso

Active control of the accordion modes of a submerged hull

This work investigates active vibration control of tonal hull axial resonances to attenuate the structural and acoustic responses of a submarine. A submerged hull can be idealised as a ring-stiffened finite cylinder with 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. Global hull modes are difficult to attenuate since passive control techniques such as damping materials and isolators are not practical due to size and weight constraints. This work numerically investigates the application of active vibration control based on a feedforward algorithm to suppress the axial and radial hull displacements. The effect of various cost functions and control arrangements on the structure-borne radiated noise is presented.