基于正向投影面积法的层析粒子图像测速权重系数计算方法  

Calculation Method of Weight Coefficient for Tomographic PIV Based on FPA

作　　者：封明军 周骛[1,3] 黄浩钦 张大鹏 高丽敏 蔡小舒 Feng Mingjun;Zhou Wu;Huang Haoqin;Zhang Dapeng;Gao Limin;Cai Xiaoshu(School of Energy and Power Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China;National Key Laboratory of Aerodynamic Design and Research,Xi'an 710129,Shaanxi,China;Key Laboratory of Multiphase Flow and Heat Transfer for Power Engineering,Shanghai 200093,China)

机构地区：[1]上海理工大学能源与动力工程学院,上海200093 [2]翼型叶栅空气动力学国家级重点实验室,陕西西安710129 [3]上海市动力工程多相流动与传热重点实验室,上海200093

出　　处：《光学学报》2023年第11期17-30,共14页Acta Optica Sinica

基　　金：国家科技重大专项(2017-V-0016-0069);翼型、叶栅空气动力学重点实验室基金(614220121050327)。

摘　　要：三维重建是层析粒子图像测速(PIV)中重要的一步,重建过程中的权重系数计算通常较为繁琐。基于此,提出一种层析PIV快速权重计算方法——正向投影面积(FPA)法,即将离散体素投影在相应像元上的面积作为权重系数计算的方法。首先,基于针孔相机模型构建三维空间内粒子多视角投影成像仿真程序,生成仿真图片用于方法分析与验证;其次,将FPA方法结合目前主流重建算法开展三维重建精度和耗时分析。结果表明,当用于本研究所述测量区域重建时,相比于传统后向方法与亚网格法权重系数计算方法,FPA法的权重矩阵元素个数分别降低了大约3个和1个数量级,计算时间分别减少了97%与85%,相应地降低了计算机的内存占用,且FPA法与传统后向方法所计算的权重矩阵的平均相似度高于0.9974。在常用实验粒子数分数(pppp=0.05)下,该方法结合目前主流重建算法的重建精度可达0.8以上。同时基于仿真图片分析了相机最佳采集角度以及实验相机噪声对重建结果的影响,结果表明,在实验噪声条件下重建结果仍然满足三维流场重建的要求。Objective Recently,tomographic particle image velocimetry(TPIV)has been widely employed in the measurement of the flow field around a cylinder,turbulent boundary layer,flame field,and other flow fields since it is highly accurate,multipoint,threedimensional,and instantaneous.The principle of TPIV is to reconstruct the threedimensional scattering intensity distribution of particles in the flow field at the adjacent time and combine the threedimensional crosscorrelation algorithm to obtain its instantaneous flow field.3D particle field reconstruction is the basis of TPIV and the premise of obtaining an accurate 3D flow field.Therefore,it is necessary to develop fast and highprecision 3D particle field reconstruction algorithms.The improvement of the reconstruction algorithm includes two aspects.The first is to improve the reconstruction accuracy,which is the similarity between the reconstructed particle field and the actual particle field,thus affecting the accuracy of the flow field.The second is to shorten the reconstruction time,since the reconstruction process needs to calculate the weight coefficient that is the intensity contribution value of spatial voxels to pixels,and iteration is adopted to update the intensity value of voxels.Thus,the reconstruction process often takes a lot of time,which is the biggest bottleneck in the TPIV application.Therefore,the calculation method of the weight coefficient plays an important role in reconstruction accuracy and reconstruction time.Methods According to the imaging principle,the line of sight received by a pixel is a spatial volume,so only some of the voxels that contribute to the intensity of a certain pixel can be fully projected into the pixel.The partially projected voxels involve the weight coefficient calculation,which is related to the setting of the camera's internal and external parameters and the spatial volume.The traditional method often employs back projection to calculate the weight coefficient.However,due to a large number of divided spatial voxels and

关 键 词：图像处理 层析粒子图像测速 三维重建 权重系数计算 正向投影面积法 

分 类 号：O359[理学—流体力学]