| With the vigorous development of laser technology,atmospheric turbulence,which restricts its application quality,has attracted widespread attention.As a mechanical wave,sound waves are accompanied by energy transfer during the propagation process,which disturb the temporal and spatial distribution characteristics of the local atmosphere.Based on this characteristic,this article provides a new idea to change the turbulence structure.Establish different sound source models,starting from the wave equation of sound waves,and according to the principle of sound wave interference superposition,numerically calculate the distribution of "artificial inhomogeneities"excited by different array sound source models;"2" based on atmospheric turbulence refractive index structure constant/3" law,combined with the random process analysis method,solves the refractive index structure constant of "artificial turbulence";performs "acousto-optic combination"to calculate the change of the transmission characteristics of light waves in turbulence under the interference of sound waves.The main content of the thesis includes:1.Explains the physical properties of atmospheric refractive index,summarizes the atmospheric refractive index measurement methods commonly used in engineering,and analyzes several different empirical formulas for calculating atmospheric refractive index based on the physical properties of the atmosphere.The definition of the atmospheric refractive index structure constant is given,and the characteristics and empirical calculation formulas of the atmospheric refractive index structure constant in the boundary layer and free atmosphere are analyzed.2.Starting from the wave equation of sound waves,analyze the disturbance characteristics of sound waves to the physical properties of the atmosphere in the process of motion.Based on the principle of interference and superposition of coherent sound waves,the calculation method of array coherent sound waves is given.Establish a "point array coherent sound source" model,and numerically calculate the spatial distribution of "artificial atmospheric pressure" and "artificial atmospheric refractive index inhomogeneity" excited by it.On the basis of a single point array sound source model,a variety of "combined array sound source" models were established,and the3.distribution of artificial refractive index inhomogeneities excited by different "combined array sound source models" in local space was numerically calculated and compared.4.Based on the "2/3 law" of the atmospheric refractive index structure constant,combined with the analytical method of the random process,on the basis of the original atmospheric refractive index structure constant,the "artificial refractive index inhomogeneity" is introduced,and the two random processes The superposition analysis is carried out,and the refractive index structure constant of "artificial turbulence" is obtained.Introduce light waves into the atmosphere disturbed by sound waves.Based on the calculation results of Fante,the long-term beam expansion radius in the "artificial turbulence" is solved.The influence of the parameter changes of the point array coherent sound source on the beam expansion radius is numerically analyzed.Above,the beam drift variance under the kolmogorov spectrum is calculated,and the influence of the sound source parameter changes on the beam drift variance is analyzed.Based on the Rytov approximation,taking the plane wave as an example,the effect of the point array coherent sound source parameter change on the light wave scintillation index is calculated and numerically analyzed.Through theoretical analysis and numerical calculations,the feasibility of coherent sound sources to change turbulence characteristics is verified,and certain theoretical support is provided for the later experiments and engineering applications of sound waves to control turbulence. |
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