摘要:
本文提出了基于光纤湍流传感器阵列的大气光学湍流空间相关函数测量原理,并确定了具体的测量方案和数据统计方法.利用光纤湍流传感器阵列在近地面开展了大气光学湍流空间相关特性的实验测量研究,尽可能全面地展示光学湍流空间相关函数的各种形式.结果表明,大气光学湍流的一维空间相关函数主要表现为两种结构形态,其一,58.7%基本符合各向同性湍流空间相关函数模型,其相关函数在一定尺度范围内呈现随尺度的增大而减小的趋势,当超过该尺度时,相关系数接近于0；其二,另有37.9%表现为与尺度无关,相关系数维持在0附近小幅度随机振荡.不难发现：光学湍流的空间相关特性主要取决于湍流的强弱和湍流是否得以充分发展,同时,湍流的相干结构将引起空间相关函数的小幅度振荡.以空间布点探测直接获取光学湍流空间相关函数的方法,不仅为分析湍流空间结构奠定了实验基础,同时,也为进一步建立非K湍流模型提供了理论开端.
Abstract:
Atmospheric optical turbulence means refractive index random fluctuation of atmosphere. In this article, according to the concept of correlation function, the measurement principle, measurement schemes, and data processing method of spatial correlation function are given based on a high-quality fiber optical turbulence sensing array. Determining the statistical time and the calculation principle of the spatial correlation is the main point of current research. Emphasis is put on demonstrating the kinds of structural forms and analyzing the impact elements of spatial correlation function in turbulence as clear as possible. Using the sensing array, experimental measurement is promoted in the near ground layer and many forms of correlation functions are revealed. Results show that there are two main structural forms of the spatial correlation function: the first one shows an isotropy-model form, which tends to decrease with the increase of spatial displacement, and then tends to zero after outer scale, the coincidence rate is about 58.7%. The other one tends to oscillate around zero, and the coincidence rate is about 37.9%. By analyzing the probability and impact elements, it is not di?cult to know that the spatial correlation of an optical turbulence mainly depends on the intensity and development degree of the optical turbulence; and the coherent structure is an important factor of oscillation in the correlation functions. On the one hand, the value of correlation coe?cient is mainly determined by the intensity of the optical turbulence; and on a certain scale, the stronger the turbulence, the bigger the value of correlation coe?cient becomes. On the other hand, the variation tendency of correlation function is not only determined by the intensity of turbulence, but also by the development degree of the optical turbulence. When the atmosphere is in advection or anisotropy, its spatial correlation coe?cient will oscillate around zero and be unrelated to the spatial displacement. The spatial correlation function obtained by the sensor array set is not only the foundation of analyzing the spatial structure, but also the beginning of giving non-Kolmogorov model of turbulence.
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