光传输中的湍流结构、成因、及表征研究

Around the basic problems of turbulence and the important application requirements related to optical transmission, this project is mainly concerned on the structure , origin and characterization of non Kolmogorov turbulence in turbulent effects to study.For this purpose,the triaxial sonic anemometer velocity and temperature time series measurements are carried out within the ASL above the land in Hefei, sea in Maoming, and snow in Antarctic for a wide range of atmospheric stability conditions.Our specific objectives are to investigate the large-scale eddy spectral characteristics. The spatial and temporal distribution of turbulence scale is studied by using the cascade and multifractal dimensional analysis method, and the existing cascade model are modified according to the experimental data. On the basis of this, the human-computer interaction interface software is developed to analyze the structure of non-kolmogorov turbulence. By measuring the temperature structure function of different spatial distance with micro temperature sensor arrays, the spatial spectrum of temperature fluctuation is constructed without the assumption of Taylor. By establishing the outer scale parameterized formula of the troposphere and stratospheric according the regional climatic characteristics of our country, the prediction accuracy of optical turbulence is improved. The ultimate goal is to build a more perfect the atmosphere turbulence model, to meet the application requirements of numerical simulation of optical transmission and turbulent effect calculation, and to provide better service for laser transmission, free-space communications, optical imaging and observatory site selection, etc.

本项目围绕湍流基本问题和光传输相关的重大应用需求，针对湍流效应中的非Kolmogorov湍流结构、成因及表征开展研究。通过三维超声风速计获取合肥陆地、茂名海面、南极雪面不同稳定度条件下的温度、风速脉动数据，研究大尺度含能区风速和温度谱特征；通过采用级串和多分形的唯相描述方法研究湍流尺度的时空分布规律，并依据实验数据对现有级串模型进行修正。在此基础上，研制出分析非Kolmogorov湍流结构的人机交互界面软件；通过不同空间距离微温传感器阵列的温度结构函数探空测量，在不涉及泰勒假定下，构造出空间温度起伏谱；通过构建符合我国地域气候特征的对流层、平流层光学湍流外尺度的参数化公式，提高光学湍流预报精度；最终目标是建立更加完善的波在大气中传输的湍流模型，进行可靠的光传输的数值模拟和湍流效应计算，为激光传输、自由空间光通讯、光学成像和天文台选址等服务。

本项目将ERA5数据、神经网络法、Thorpe尺度、Ellison尺度等用来估算和预报近地面湍流和高空湍流廓线，并将湍流参数化研究成果应用到南极天文选址中。成果发表在Applied Optics、Optics express、Optical Society A、Monthly Notices of Royal Astronomical Society等有影响的期刊上；针对临近空间湍流测量空间分辨率要达到1cm的技术挑战,，研制了可测量毫米尺度的湍流原位测量仪；2019年7月、8月和2020年8月圆满完成了由中科院天空信息研究院牵头的临近空间科学实验战略性先导专项（鸿鹄专项）在青海省大柴旦地区3次平流层长航时大气湍流原位测量综合性试验。获取了浮空器在21- 22km平飞阶段UTLS（Upper Tropospere and Lower Stratosphere 湍流强度数据和湍流谱数据。分别用5um和1um微温探头测量的温度脉动时间序列数据，首次观察到大气本底噪声和强湍流信号交替出现，处于本底噪声的大气有时几乎没有温度起伏。风速湍流廓线数据中出现此类现象已有文献报道，平飞温度湍流数据出现这样的现象未见报道；提出了定量识别UTLS温度湍流结构如湍流层个数、湍流层水平尺度、湍流层水平间距、水平尺度内的湍流占比等参量来描述湍流结构的2种方法。该方法用来识别温度湍流结构尚未见报道；开展了UTLS湍流标度律初步研究。UTLS水平方向湍流中观测到大气温度湍流遵从Kolmogorov标度律存在的比例很小。这些成果对天文、光传输、光通信等领域具有十分重要的意义。. 本项目按照计划书在规定时间内完成了各项研究内容，达到了预期目标。课题共发表论文12篇(SCI 6篇，EI 2篇，核心4篇)，6篇SCI待发表，国内学术会议做学术报告12人次，提交发明专利2项。培养1名博士毕业，2名硕士毕业。在读博士生5名，硕士生2名，1名博士生获2020年度博士研究生国家级奖学金 。