Understanding the physical features of the flow noise for an axisymmetric body is important for improving the performance of a sonar mounted on an underwater platform. Analytical calculation and numerical analysis of ...Understanding the physical features of the flow noise for an axisymmetric body is important for improving the performance of a sonar mounted on an underwater platform. Analytical calculation and numerical analysis of the physical features of the flow noise for an axisymmetric body are presented and a simulation scheme for the noise correlation on the hydrophones is given. It is shown that the numerical values of the flow noise coincide well with the analytical values. The main physical features of flow noise are obtained. The flow noises of two different models are compared and a model with a rather optimal fore-body shape is given. 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. The loss of noise diffraction has a great effect on the flow noise from boundary layer transition. Meanwhile, 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. Furthermore, the flow noise received by the acoustic array has lower correlation at a designed central frequency, which is important for sonar system design.展开更多
Understanding the physical features of the diffracted sound field on the surface of an axisymmetric body is important for predicting the self-noise of a sonar mounted on an underwater platform. The diffracted sound fi...Understanding the physical features of the diffracted sound field on the surface of an axisymmetric body is important for predicting the self-noise of a sonar mounted on an underwater platform. The diffracted sound field from the transition region of an axisymmetric body was calculated by the geometrical theory of diffraction. The diffraction ray between the source point and the receiving point on the surface of an axisymmetric body was calculated by using the dynamic programming method. Based on the diffracted sound field, a simulation scheme for the noise correlation of the conformal array was presented. It was shown that the normalized pressure of the diffracted sound field from the transition region reduced with the increases of the frequency and the curvature of the ray. The flow noises of two models were compared and a rather optimum fore-body geometric shape was given. Furthermore, it was shown that the correlation of the flow noise in the low frequencies was stronger than that in the high frequencies. And the flow noise received by the acoustic array on the curved surface had a stronger correlation than that on the head plane at the designed center frequency, which is important for sonar system design.展开更多
A vulcanized rubber layer is usually used on the head of an axisymmetric body to keep it streamlined and watertight.The elastic boundary condition is considered when the flow noise of an axisymmetric body is calculate...A vulcanized rubber layer is usually used on the head of an axisymmetric body to keep it streamlined and watertight.The elastic boundary condition is considered when the flow noise of an axisymmetric body is calculated,and we employ the mutual coupling method between the vulcanized rubber layer and the How around to solve the flow-noise field for an axisymmetric body in water.The results show that the deformation of the vulcanized rubber layer is reduced with the increase in Young's modulus.The Young's modulus of the rubber material should be large enough to keep it streamlined,and the noise power levels in the peak of the axisymmetric body are smaller than the other positions,which provides us with important theoretical support for laying acoustic arrays on the head of the body.展开更多
基金Project supported by the National Natural Science Foundational of China (Grant No. 10774119)the Program for New Century Excellent Talents in University, China (Grant No. NCET-08-0455)+1 种基金the Natural Science Foundation of Shaanxi Province of China (Grant No. SJ08F07)the Foundation of National Laboratory of Acoustic and the Foundation for Fundamental Research of Northwestern Polytechnic University, China (Grant No. 2007004)
文摘Understanding the physical features of the flow noise for an axisymmetric body is important for improving the performance of a sonar mounted on an underwater platform. Analytical calculation and numerical analysis of the physical features of the flow noise for an axisymmetric body are presented and a simulation scheme for the noise correlation on the hydrophones is given. It is shown that the numerical values of the flow noise coincide well with the analytical values. The main physical features of flow noise are obtained. The flow noises of two different models are compared and a model with a rather optimal fore-body shape is given. 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. The loss of noise diffraction has a great effect on the flow noise from boundary layer transition. Meanwhile, 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. Furthermore, the flow noise received by the acoustic array has lower correlation at a designed central frequency, which is important for sonar system design.
基金Project supported by the National Natural Science Foundational of China (Grant No.10774119)the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No.NCET-08-0455)+2 种基金the Natural Science Foundation of Shaanxi Province of China (Grant No.SJ08F07)the Foundation of National Laboratory of Acoustics of Chinathe Foundation for Fundamental Research of Northwestern Polytechnical University of China (Grant No.2007004)
文摘Understanding the physical features of the diffracted sound field on the surface of an axisymmetric body is important for predicting the self-noise of a sonar mounted on an underwater platform. The diffracted sound field from the transition region of an axisymmetric body was calculated by the geometrical theory of diffraction. The diffraction ray between the source point and the receiving point on the surface of an axisymmetric body was calculated by using the dynamic programming method. Based on the diffracted sound field, a simulation scheme for the noise correlation of the conformal array was presented. It was shown that the normalized pressure of the diffracted sound field from the transition region reduced with the increases of the frequency and the curvature of the ray. The flow noises of two models were compared and a rather optimum fore-body geometric shape was given. Furthermore, it was shown that the correlation of the flow noise in the low frequencies was stronger than that in the high frequencies. And the flow noise received by the acoustic array on the curved surface had a stronger correlation than that on the head plane at the designed center frequency, which is important for sonar system design.
基金Supported by the National Natural Science Foundation of China under Grant No 11174235the Science and Technology Development Project of Shaanxi Province(No 2010KJXX-02)+1 种基金the Program for New Century Excellent Talents in University(No NCET-08-0455)the Excellent Doctorate Foundation of Northwestern Polytechnical University.
文摘A vulcanized rubber layer is usually used on the head of an axisymmetric body to keep it streamlined and watertight.The elastic boundary condition is considered when the flow noise of an axisymmetric body is calculated,and we employ the mutual coupling method between the vulcanized rubber layer and the How around to solve the flow-noise field for an axisymmetric body in water.The results show that the deformation of the vulcanized rubber layer is reduced with the increase in Young's modulus.The Young's modulus of the rubber material should be large enough to keep it streamlined,and the noise power levels in the peak of the axisymmetric body are smaller than the other positions,which provides us with important theoretical support for laying acoustic arrays on the head of the body.
