Research On Acoustic Scattering Characteristics Of Under-Ice Rough Surface Based On Kirchhoff Approximation

With the development and utilization of Arctic waterways,Arctic underwater acoustic has become a hot issue in Arctic research.Most areas of the Arctic are covered by the natural ice layer,which will affect the sound wave propagating in the water.Therefore,it is of great significance to study the three-dimensional acoustic scattering characteristics of the Arctic ice layer for modeling of under-ice sound field and studying of under-ice acoustic communication.Aiming at the problem of acoustic scattering of the under-ice rough surface,this paper starts from studying the two-dimensional acoustic scattering characteristics of the rough surface,calculates the scattering intensity of the one-dimensional rough surface by Kirchhoff approximation method(KAM),and compares with the numerical results calculated by integral equation method(IEM).The validity of KAM for the study of acoustic scattering characteristics of the rough surface is verified.Since the lower surface of the Arctic ice layer is a two-dimensional under-ice rough surface,an analytical model of three-dimensional acoustic scattering characteristics of the under-ice rough surface is first established by KAM,and the concept of the local statistical average reflection coefficient of the under-ice rough surface is defined in the model.The analytical expression of the scattering intensity of the under-ice rough surface is derived and the scattering characteristics of the under-ice rough surface at different surface parameters and incident angles of sound wave are analyzed.Secondly,a numerical model of three-dimensional acoustic scattering characteristics of the under-ice rough surface is established by KAM.The scattering intensity of the under-ice rough surface is calculated by plate element method(PEM),and compared with the results of the analytical model,and the influence of the under-ice rough surface roughness is analyzed.Finally,the experiment of measuring the scattering intensity of the under-ice rough surface in water tank is performed.The scattering intensity at different incident angles of sound wave is measured,and the results are compared with those of the analytical model and the numerical model.The experimental results show that when the incident angle of sound wave is 0° and 15°,the error between the experimental measured results and the theoretical model calculation results is small,which proves the validity of the theoretical model when the sound wave is incident at a small angle;when the incident angle of sound wave is 30°,the error between the experimental measured results and the numerical model calculation results is small,and the error between the analytical model calculation results is large,which proves the shortcomings of the analytical model when the sound wave is incident at a large angle.