Research On Propagation Characteristics Of Complex Ocean Sound Based On Finite Element Method

Numerical simulation and sound field analysis of ocean sound field is one of the main ways to study the law of sound signal propagation in the ocean.With the decrease of the working frequency of sonar,in the shallow sea environment,part of the acoustic signals can penetrate deeper into the seabed and be reflected back to the sea surface,so the influence of transverse waves cannot be ignored in the modeling process;at the same time,low-frequency acoustic signals can travel long distances Therefore,the influence of the horizontal unevenness of the medium and the undulation of the sea floor on the sound propagation characteristics cannot be ignored.Therefore,the horizontal deflection of sound energy needs to be considered in the modeling process.In the traditional modeling process,in order to simplify the calculation,researchers usually make different degrees of approximation and assumptions to the wave equation.Therefore,the sound field results when calculating the complex ocean environment are quite different from the actual ocean sound field.At the same time,with the increasing requirements of researchers on the marine sound field modeling and simulation environment in recent years,the constructed marine sound field environment is more and more in line with the actual marine sound field environmental parameters and topographic characteristics,so the use of traditional sound field calculation methods will be very useful.It is difficult to obtain sound propagation characteristics that match the actual complex ocean environment.This article mainly chooses the finite element method to simulate and calculate the sound propagation characteristics in a complex ocean environment.On the basis of verifying that the finite element method can accurately solve the sound field characteristics of various complex marine environments,based on the sound wave theory and the ray theory,the sound propagation laws in the complex marine environment and the complex seabed environment are discussed separately: the existence in the sea layer is mainly discussed The law of sound propagation under mesoscale vortex physical ocean phenomena;in the seafloor,the influence of cone-shaped seamounts on the sound propagation characteristics is considered in the seafloor.At the same time,based on the scaled-down test,the calculation results of the complex ocean environment sound field based on the finite element method are verified Accuracy.The main conclusions of the study are as follows:(1)The acoustic propagation characteristics under the two-dimensional axisymmetric and three-dimensional models calculated based on the finite element method are basically consistent with the acoustic field results calculated by RAM,COUPLE and the global coupled normal wave model(DGMCM model),which proves the calculation based on the finite element method The accuracy and precision of the sound field results obtained.(2)Mesoscale vortices are ocean phenomena that are ubiquitous in the ocean.When acoustic signals propagate in an ocean environment with mesoscale vortices,the strength and nature of the vortices can affect the propagation characteristics of the acoustic signals.The cold vortex will make the sound convergence zone approach the sound source,the span of the convergence zone will decrease,and the convergence gain will increase;the warm vortex will make the convergence zone far away from the sound source,the span of the convergence zone will increase,the sound rays will spread,and the convergence gain will decrease;and the vortex The greater the intensity,the greater the impact on the movement and gain of the convergence zone.(3)When the seabed terrain has undulations,due to the deflection of sound energy in the horizontal direction,the use of cylindrical symmetry models can no longer accurately calculate the three-dimensional sound field.When the seabed is horizontal,the sound field simulation results in the cylindrical coordinate system and the three-dimensional rectangular coordinate system are basically the same;when the seabed terrain has undulations,due to the deflection of the sound energy in the horizontal direction,the simulated sound propagation loss results in the three-dimensional rectangular coordinate system It is larger than the result of sound propagation loss simulated in cylindrical coordinate system.A scaled-down experiment was carried out in a 2m×1m×1m stainless steel pool,and the correctness of the above conclusions was verified by comparing the simulation results of the two coordinate systems with the results of the scaled-down experiment.