High Frequency Acoustic Scattering Characteristics On Condition Of Floating Ice Hockey

There are a lot of sea ice floating off the ice shelf in the polar ice area,which will drift to the low latitude ocean with the action of ocean currents,they are great threats to ship.The study of sea ice scattering characteristics at sea-water interface is the precondition of detecting and avoiding ice for ships.The sea ice floating on the water surface belongs to the target near the interface in the physical model.Because of the existence of the interface,the target echo near the interface adds two additional waves compared with the target echo in the free field,the echo characteristics of the target near the interface are more complex.The scattering characteristics of the target near the interface are an important research content in the field of target acoustic scattering.In this context,the scattering characteristics of floating ice hockey balls at high frequencies are studied in order to provide technical support for the development of navigation vessels and routes in polar area.First,the impedance of the ice surface is studied,then we deduce the reflection coefficients of the ice surface at different incident angles and frequencies.Secondly,the plate element method based on Kirchhoff approximation for calculating the scattering field of a spherical object in free field is studied and verified by the eigenfunction expansion method.The accuracy of the plate element method in calculating the target strength is verified by simulation,and a theoretical model for calculating the target strength is established.The model is applied to rigid spheres and ice hockey balls on floating water surface.The water surface has a great influence on the scattering field of the target,and two additional waves will be introduced directly: bistatic scattering wave and virtual source scattering wave.Considering the limitation of the eigenfunction expansion method in calculating the scattering sound field of the target near the interface,the plate element method is extended to the scattering field calculation of the floating target on the water surface.Finally,the target strength measurement experiments of water tank are carried out to measure the target strength of copper balls and ice hockey balls in free field,and the target strength of copper balls and ice hockey balls in floating state.The experimental results show that the modified plate element method can accurately calculate the target strength of floating ice hockey balls in high frequency.The theoretical model of acoustic scattering characteristics and target intensity calculation of floating ice balls studied in this paper has a certain reference value for the subsequent development of floating ice detection and collision avoidance sonar,and provides a guarantee for navigation safety in the sea area near the polar region.