Theories And Application Research Of Computational Flow Imaging

Computational flow imaging (CFI) uses theoretical predictions of the interaction and transmission of optical waves through theoretical flowfield to generate digital pictures that simulate real observations. It was used to construct flow visualization corresponding to shadowgraph, schlieren, interferometric and Planar Laser Induced Fluorescence (PLIF) images. By providing a better insight into the flow physics and CFD code behavior, CFI is proving to be extremely useful to experimentally validate CFD codes. In essence it is the art and science of generating digital images of theoretical fluid dynamic phenomena in formats that mimic optical observations of real flowfield.This dissertation is about theories and applications research of CFI, includes four main parts:First, the theoretical modeling of Computational Flow Imaging corresponding to shadowgraph, schlieren, interferometric and Planar Laser Induced Fluorescence (PLIF) is developed.Second, a parallel adaptive ray-casting algorithm for graphic rendering of CFI is developed. In the computational model of CFI, the line-of-sight integration is difficult to obtain for 3D complicated flow field, because curvilinear grids, multizone curvilinear grids, and other irregular grids that are commonly used in computational fluid dynamics (CFD) present interesting challenges, such as the complex shapes of cell regions defined by grid points; the wide variation in the sizes of cells in different regions of the grid; and the intersecting or overlapping nature of multi-grids. The parallel adaptive ray-casting algorithm is extremely efficient to solve these problems.Third, a very useful colored CFI-Interferometry is developed. As the result of the presence of Shockwaves, or because of the spots of light, scattering, diffraction and other phenomena hiding the information searched in the experiment, discontinuities of the fringes are found in the interferogram of high-velocity gas flows. Colored CFI-Interferometry is a powerful tool to overcome these problems.Last, a new idea of using CFI to fuse numerical simulating results into Optical Computerized Tomography(OCT) reconstruction is proposed to make up the lack of information in the case of incomplete data.