时变正交光偏折投影场定量视频测量及其三维重建

It is suitable to measure the time-series data of orthogonal projected ray deflection fields by background oriented Schlieren techniques for the high-speed and hypersonic wind tunnel testing, but the 3D reconstruction with this sort of data is ill-posed mathematically. Therefore, a new method and novel ideas for ray trace and complex flow field visualization with time-varying in wind tunnel testing, is explored by this project: ①to reveal the mechanism of measuring errors for the orthogonal projected ray deflection fields under the multi-scale flow field structures with time-varying, the calibration methods of the projected ray deflection fields are researched, the multiple-parameter(including the background design parameters, optical path parameters, the time/space resolution of camera, multi-scale flow structural parameters) measuring error control and its sensitivity analysis models are created to minimize the measuring error of orthogonal projected ray deflection fields; ②a mining model for association features between multi-scale flow structural and orthogonal projected deflection fields are studied, the construction method of spatial basis functions and the methods to extract the prior knowledge are established, a new method of 3D reconstruction of orthogonal projected ray deflection fields with the additional non-feature structures model is presented, the 3D reconstruction results from non-feature structures affect model, is overlaid to 3D reconstruction of feature structures achieving by the spatial basis functions of the large-scale flow structure, then, the problems of underdetermined systems and high computational complexity faced by 3D reconstruction of orthogonal projected ray deflection fields, are solved. The experiments are carried out to evaluate and improve the method and the model established in this project.

背景纹影技术适于在高速与高超风洞试验中测得正交光偏折投影场时序数据，但这类数据的三维重建在数学上属不适定问题，故，本项目探索风洞试验中的光传输轨迹测量与时变复杂流场显示新方法、新观念：①揭示多尺度时变流场结构下正交光偏折投影场测量误差的产生机理，研究光偏折投影场定量测量的标定方法，创建多参数（包括背景设计参数、光路参数、相机时间/空间分辨参数、多尺度流动结构参数）的正交光偏折投影场测量误差控制及其敏度分析模型，最小化测量误差；②研究流动结构与正交光偏折投影场结构的时空关联特征挖掘模型，建立先验知识提取方法和空间基函数构造方法，提出附加正交光偏折投影场非特征结构影响模型的流动结构三维重建新方法，即利用大尺度流动结构空间基函数重建流动特征结构，再叠加非特征结构影响模型重建的流动结构，解决正交光偏折投影场三维重建面临的欠定与高计算复杂度问题。开展实验研究，分析、评价和完善所建立的方法与模型。

背景纹影技术适于在高速与高超风洞试验中测得正交光偏折投影场时序数据， 但这类数据的三维重建在数学上属不适定问题，故，本项目探索风洞试验中的光传输轨迹测量与时变复杂流场显示新方法、新观念：. 1）为了定量显示空腔高速复杂流动结构，本文采用均布的小圆点作为背景纹影（BOS）的背景点，利用视频测量(VM)成熟的小圆点图像定位与匹配技术，克服了现有图像互相关技术对BOS的限制；另一方面，推导非平行光穿过流场的偏折位移/角计算公式，基于VM的共线方程，准确计算从背景点到相机摄影中心的光束穿过流场产生的偏折位移场和光程差场。FL-21风洞的某空腔高速（0.6≤Ma≤2.0）复杂流动结构的视频测量结果表明：本方法可清楚分辨出亚微米量级的光程差差异与微弧度量级的偏折角差异，定量显示空腔高速流动产生的波/涡/剪切层的位置、强弱及其相互关系，为复杂流动结构与气动光学效应的测量与显示提供新的途径，其光路简单、无需价格昂贵的相干光源，因此，具有巨大应用前景。. 2）建立了光偏折位移场视频测量的灵敏度计算公式,在微弱压缩波测量中得到应用，其中测得的10度锥头部微弱压缩波马赫角与理论值吻合。. 3）提出联合目标特征的光学偏折场的代数迭代重建方法，以及约束添加方法和求解方法等。最后，通过喷射气流的模拟实验，实现了约束条件下流场的近似重建，验证了本文方法的可行性和正确性。. 4）建立的光偏折位移场视频测量技术，已应用到国防973（613240）项目“大尺度空腔高速复杂流动/振动/噪声耦合机理及控制方法研究”，直接作为在研军机型号弹舱及内埋武器系统研制的空腔流动/振动/噪声集成观测，为流动/振动/噪声耦合特性提供观测手段，评估验证流动/振动/噪声特性。