Research On Iterative Reconstruction Method Of 3D Density Distribution Of Tomo-PIV

Tomographic Particle Image Velocimetry(Tomographic PIV)is an advanced optical measurement technology,which can quantitatively obtain the structure of three-dimensional stereoscopic flow field.It can be used as an effective measurement method for turbulence,multi-vortex interference and other three-dimensional complex flow field,solve the measurement problems of traditional PIV system such as particle overlap,complex flow field structure and large measurement error,and obtain the corresponding pressure field,sound field and other physical field information.It is of great significance for the study of unsteady flow phenomena.Based on the real wind tunnel measurement background,this paper studies the key technologies in tomography PIV,and derives a more accurate mathematical model of 3D particle field imaging.Based on the model,the 3D particle field is accurately reconstructed,and the factors affecting the reconstruction are detailed.After analyzing,the reconstructed 3D particle field is transformed into a 3D velocity field,and the reconstruction velocity field error is analyzed.Finally,the tomographic PIV numerical simulation test platform is built based on the above research.Specific research includes three-dimensional particle field imaging,three-dimensional particle field reconstruction,and three-dimensional velocity field motion analysis.In three-dimensional particle field imaging,two laser illumination systems are designed to illuminate the flow field.The selection and distribution of tracer particles in the flow field are discussed.The light scattering characteristics of tracer particles are analyzed.Based on the imaging principle of CCD camera and the scattering principle of tracer particles,the imaging model of three-dimensional particle field is established,and simulation results show that the model is effective.Then,in the three-dimensional particle field reconstruction,the three-dimensional particle field reconstruction model is deduced based on the particle imaging model,and various three-dimensional reconstruction algorithms are analyzed and compared.The applicability of MART three-dimensional particle field reconstruction algorithm is expounded.The algorithm is simulated,and the results of three-dimensional particle field reconstruction and the influencing factors and three-dimensional reconstruction are analyzed and compared.The speed and memory of the reconstruction algorithm are discussed.In the motion analysis of three-dimensional velocity field,the theory of motion analysis is introduced.The key FFT fast cross-correlationalgorithm is discussed and simulated.The program is written to realize the three-dimensional reconstruction of velocity field,and the results are analyzed quantitatively.Finally,a graphical user interface program is written,and the above software modules are integrated into the software of the numerical simulation test platform of the tomographic PIV.The input and running results of the mathematical model and reconstruction algorithm in the tomographic PIV are visualized.Building the PIV numerical simulation test platform has no expensive equipment cost and is easy to implement.The key algorithm of tomography PIV can be simulated and verified,and the effectiveness of the algorithm is quantitatively analyzed.Tomographic PIV numerical simulation test platform can be used to guide experimental design,planning and error analysis,among which three-dimensional reconstruction software and motion analysis software can be directly used in the experiment.At the same time,this paper proposes a more effective tracer particle imaging model on the original tomographic PIV algorithm,which plays an important role in the accurate reconstruction of the 3D particle field.Based on the improvement of the 3D reconstruction algorithm of the model,the guaranteed particle field is further improved.The applicability of reconstruction.Through the research in this paper,it is beneficial to promote the development of domestic three-dimensional tomography PIV technology,and provide a great help to the application of the technology in the actual wind tunnel.