Flow noise from the transition region of an axisymmetric body in water

Abstract

Flow noise from transition region of an axisymmetric body is important for predicting the self-noise of a sonar mounted on an underwater platform. Numerical calculation of the flow noise for an axisymmetric body is presented and the diffracted loss on the head surface of the body is calculated by the geometrical theory of diffraction. The main physical features of flow noise are obtained. The flow noise in horizontal symmetry profile of the axisymmetric body is non-uniform, but it is omni-directional and has little difference in the cross section of the body. Based on the simulation, the noise power level increases with velocity to approximately the fifth power at high frequencies, which is consistent with the experiment data reported in the literature. Meanwhile, the flow noise received by the acoustic array on the curved surface has a stronger correlation than that on the head plane at the designed center frequency, which is import for sonar system design. Furthermore, the flow noises of two models with different shapes are compared and a rather optimum fore-body geometric shape is given.