Study On Acoustic Scattering Model Of Ice-water Mixing Interface Based On Kirchhoff

With the increase of global temperature,the sea ice in the polar region began to melt in large area,resulting in the gradual decrease of ice coverage area,so more and more countries began to pay attention to the development of polar channels.When the ship is sailing in the polar region,the floating ice on the sea has a strong acoustic scattering effect on the active acoustic equipment.The reverberation interference brought by these scattering has a great influence on the performance of the active acoustic equipment under the ice.Therefore,the research on the scattering characteristics of floating sea ice is the precondition for the normal operation of the ship in the polar region.The sea ice floating on the polar sea belongs to the target near the interface in physical model.Compared with the target in free space,due to the existence of the interface,the echo of the target will introduce two additional waves,resulting in complex echo characteristics.On this basis,this paper studies the acoustic scattering model of ice water mixed interface of ice floe based on Kirchhoff approximation.Around the research object,this paper first studies the scattering sound field of the sphere in the free field,compares the strength results of the rigid sphere and the ice sphere.It is found that the target strength of the ice sphere in the free field is smaller than that of the rigid sphere,and the difference is related to the reflection coefficient of the ice sphere surface.Secondly,based on Kirchhoff approximation,the scattering sound field of the sphere in the floating state is studied.According to the result of formula derivation,it can be seen that the structure of the target echo of the sphere in the floating state is very complex.Because of the existence of water surface,two additional waves are introduced into the target echo: bistatic scattering wave and virtual source scattering wave.Considering the limitation of Kirchhoff approximation theory,a numerical method is introduced to compare the analytical solution of a single sphere in free field and floating state with the numerical solution.It is further extended to the floating sphere interface without considering the multiple scattering between the spheres.Finally,the water tank experiment is carried out to measure the target strength of a single sphere in free field and floating state,as well as the scattering strength of ice water mixed interface of multiple floating ice spheres.