| With the development of social politics and economy,limited land resources are increasingly consumed,and there is a danger of over-exploitation.In order to implement the idea of sustainable development,the development of the marine sector has become the top priority of the country in establishing its development strategy.Marine surveys and resource development have accelerated the development of underwater target detection technology.At present,the contact type underwater acoustic positioning technology and non-contact laser acoustic remote sensing technology composed the underwater target detection technology commonly.Advantage of the laser remote sensing technology is real-time,non-destructive,and high sensitivity characteristics,it is becoming the current underwater an important method of target surveying.In this thesis,the acousto-optic diffraction method is used to study the diffr-action pattern of the liquid surface wave,and the physical characteristics of the liquid surface wave are obtained,so as to obtain the relevant information of the underwater low-frequency sound source.This paper mainly studies the following aspects:(1)According to the theory of fluid mechanics and water wave,the acousto-optic diffraction effect of liquid surface wave and the microwave theory of water surface are briefly described.The characteristics of liquid surface wave are analyzed,and the dispersion relation of transverse microwave on water surface and the fluctuation of microwave on water surface are obtained.The equation and the wavelength formula of the water surface microwave theoretically verify that the underwater low-frequency sound source is related to the physical characteristics of the liquid surface wave.By detecting the surface wave of the liquid,the information of the underwater sound source can be reflected.The optical effect method provides theoretical support for detecting underwater low frequency sound sources.(2)Using the acousto-optic diffraction method to explore the position of underwater low-frequency sound source.Due to the attenuation of sound propagation,the amplitude of the surface wave of the liquid is negatively correlated with the distance from the sound source to the waveform converter.In the experiment,the acousto-optic diffraction method is used to obtain the diffraction pattern of the surface wave of the liquid under different conditions,and the amplitude of the surface wave of the liquid is studied the relationship of distance.Through the improvement of the previous experimental device,the depth of the underwater sound source is changed by using the lifting platform to realize the detection of the underwater low-frequency sound source depth;the waveform conversion system is established,and its position on the water surface is changed to realize the detection of the horizontal position of the underwater low-frequency sound source.Thereby,the three-dimensional positioning of the underwater low frequency sound source is determined.(3)Exploring the attenuation law of underwater acoustic waves by acousto-optic diffraction method.Since the sound propagation is attenuating,the attenuation of the underwater acoustic wave is obtained by studying the wave amplitude of the liquid surface.In the experiment,the waveform converter is sequentially moved along the X axis on the water surface to obtain the diffraction pattern at different positions.After the data processing,the variation of the liquid surface wave amplitude is obtained.Since the underwater low frequency acoustic signal is associated with the liquid surface wave,the water is obtained.The attenuation law of the lower sound wave propagation process:when the output power of the underwater sound source is constant,observe the image of the surface wave amplitude of the liquid source at different output frequencies,and obtain the attenuation law of the underwater sound wave with the output frequency;Timing,observe the image of the surface wave amplitude of the liquid at different output voltages,and obtain the attenuation law of the underwater sound wave with the output voltage.(4)The attenuation law of underwater sound waves in the parallel direction of the liquid surface.The moving path of the wavefonn converter moves horizontally,and the position of the waveform converter changes accordingly.The diffraction pattern with clear,stable and high contrast is observed.After the data processing,the variation of the amplitude of the liquid surface wave is obtained,and then the attenuation of the underwater acoustic wave is obtained.The rate is independent of the path in which the parallel moving waveform converter moves. |
