Influence Of Shallow Water Internal Solitary Waves On Sound Propagation

Internal wave is universal in ocean, which causes variation of temperature-salinity structure with range and depth, thus changes the sound speed profile. There will be strong fluctuation of sound signal amplitude and phase, when sound signal transmitted through the internal waves. So it is important to study the influence of internal wave on sound propagation.There is a broad coastline in our country. In continental shelf sea areas, there are lots of observations of large amplitude internal solitary waves. The internal solitary waves cause serious threat on oil drilling platform and undersea oil pipelines, making it more challenge for submarine detection. One important topic of underwater acoustics is the modeling of sound propagation for three-dimensional complex environment with internal wave, vortex, and frontal. The thesis presents comprehensive theoretical, numerical and experimental investigations on sound propagation with internal solitary waves in three dimensional complex environments.The researches about internal waves had been introduced in thesis, and the researches about its influence are briefly summarized. The three-dimensional sound ray refraction effect by given internal solitary wave model had been analyzed using ray theory. Then the fluctuation of sound wave propagating through moving internal solitary wave had been analyzed using method of coupled mode, and the influence of internal solitary wave on sound signal amplitude, phase and energy under different conditions had been analyzed using parabolic equation method. The influence of solitary wave on acoustic vector field and beam-forming had also been simulated.The temperature data and acoustic signal fluctuation data with internal solitary waves was obtained in 2009 sea experiment. The measured data is analyzed first, and sound propagation is simulated using parabolic equation method with measured parameters of ocean environment, then the simulation results had been compared with measurements. Results show that the parabolic equation method in case with internal solitary waves is simple and effective. The analyzing method and some conclusions given in the thesis can be used as reference for engineering works.