Abstract
Three-dimensional density distribution can be reconstructed using tomography technique from interferogram images. Conventional tomography techniques have low accuracy with a few interferogram images and truncated images. To improve the accuracy of the reconstruction, a new tomography technique is proposed. In the present method, density distribution is assumed to be mainly effected by diffusion processes, and to be expressed as the summation of elementary density distributions. The tomography is carried out as the optimization of the arrangement of elementary density distributions. As optimization technique, genetic algorithm (GA) is introduced.
The GA usually needs lots of calculation time. In this study, the two-dimensional density distribution in cross sections are stacked, in order to construct the three-dimensional data. As an initial condition of one cross section, the converged data at previous cross section are used, resulting in the less calculation time.
The three-dimensional density distribution is reconstructed using the present method (GA) and conventional Filtered Back Projection method (FBP). The target flow field is density stratified field, which is caused by the downward helium jet into air. Both the GA and FBP can reconstruct the three-dimensional density distributions. The GA shows high effectiveness with reconstructing the three-dimensional data with a few images and truncated images.
