The Spectral Element Method Applied To Ocean Acoustic

Numerical modeling of ocean sound propagation has been a popular subject in the field of underwater acoustic, wherein calculating analytic solutions, time domain simulation, included the impact of complex marine environmental have always been the main subject investigated.Aiming at the issue for the two-dimensional ocean sound field, this paper introduces spectral element method using SPECFEM2D program to build a two-dimensional waveguide model,and analyses different ocean sound field in time domain and frequency domain. In addition,using the ability of SPECFEM2D adjoint method to calculate the inverse problem, the paper calculate the sensitivity kernels of two-dimensional sound field propagation time .In the studies of two-dimensional sound propagation, this paper sets up the models of horizontal seabed, wedge seabed and complex seabed respectively, demonstrates the feasibility of spectral element method applied to ocean sound propagation. In simulation of horizontal seabed model, at first comparing with other methods, the accuracy of results calculated by the SPECFEM2D program of Spectral Element Method are verified. Furthermore time-domain results using program to calculate are analyzed. Finally the paper simulates the effects of three different bottoms on acoustic propagation. In simulation of sound propagation in wedge waveguide, the influences of shear wave on sound propagation and phenomena of interface wave arised in the process of wave propagation are analyzed by comprehensive comparison. In simulation of complex seabed model, sinusoidal shape bottom is chosen. The analysis of its time-domain waveform received and complex sound field structure was carried out.In addition to the above, this article also describes the adjoint method often used in seismic tomography and calculates the sensitivity kernels of two-dimensional sound field propagation time by using the SPECFEM2D program. The impacts of perturbation of parameters of several different models respectively on the propagation time of the direct wave, the interface wave and the reflected wave of the sea surface are studied. these studies provide new ideas for the development of ocean acoustic tomography technology.