Research On The Application Of Multi-stage Fast Marching Method In Forward Simulation Of Ocean Sound Field

Multilevel Fast marching method is one of the most commonly used travel time calculation methods in the field of geoacoustics.It is widely used in the fields of ray tracing and tomography for its high efficiency,high accuracy and multi-value travel time calculation ability.In the field of ocean acoustics,the traditional ray-acoustic methods(such as Bellhop)can not solve the problems of sound diffraction and the propagation of two-layer media on the seabed,there are some limitations in the calculation of sound field in shadow area and the influence of complex seabed on sound field.In this paper,a new ray tracing method in the field of geoacoustics,and Multilevel Fast marching method,is introduced,this paper attempts to solve the problem of the sound field in the ocean sound shadow area and the description of the propagation path of the double bottom sound.First,the basic theory of the Fast marching method is studied,and the applicability of the Multilevel Fast marching method in ocean acoustic field forward modeling is optimized and improved,in order to solve the problem of time path data sorting in Multilevel Fast marching method,a new heap sorting method,the space sink method,is introduced to improve the data heap sorting rate Secondly,in order to solve the problem of low accuracy of travel time calculation near sound source caused by abnormal increase of curvature near sound source in grid-like ray tracing,the double-grid encryption method is introduced to encrypt the grid near sound source,the third is to use cubic b-spline interpolation method to smooth the interface and improve the accuracy of travel time calculation.The results show that the improved Multilevel Fast marching method has a positive effect on improving the accuracy and efficiency of computation.Secondly,this paper based on the improved fast algorithm,through the program module design,model parameter settings,the sound field simulation model under the condition of uniform sound velocity gradient at the horizontal interface in shallow water,the sound field simulation model under the condition of deep sea horizontal interface with sound channel and the sound field simulation model under the condition of complex interface are established respectively,the applicability and feasibility of Multilevel Fast marching method for ray tracing in ocean acoustic propagation models were also studied.Finally,the simulation results of ocean acoustic field based on Multilevel Fast marching method in different scenarios are analyzed and evaluated,firstly,the ray-tracing model under the condition of the single-layer media seabed model is simulated,and the results are compared with the ray-tracing results constructed by bellhop,the results show that the sound propagation path and travel time of the two Fast marching method are basically identical,which proves the validity of the multistage sound field in the calculation of ocean sound field The second is the analysis of the simulation results of the ocean acoustic field under the condition of the two-layer medium seabed model,which shows that the ray tracing in the acoustic shadow area can be realized based on the fast algorithm,the ray path simulation of a two-layer media model of the sea-water Island-reef area was carried out by using a Multilevel Fast marching method to track the acoustic propagation path inside the Island-reef area.