Study On Unsteady Flow Field Deflectometric Tomography Based On The Reconstruction Of Compressed Sensing

The measurements of unsteady flow field is become a new hotspot with thedeveloping of engineering thermophysics and dynamics. Optical deflectiontomography has become a powerful tool in the measurement of complex flow fieldbecause of its advantages, such as low sensitivity, non-contact measurement andanti-interference ability. Existing optical deflection tomography technology cannotachieve synchronous sampling and reconstruction under few view-angles projections.Thus the application of optical deflection CT technology is subject to the developmentof its sampling technique and reconstruction algorithm.Based on the principle of digital micromirror device, a moire tomographyprojection sampling system is presented for obtaining the chronological arrays ofmultidirectional deflectograms. Deflection projections in different angles of view canbe captured synchronously in same optical path condition by high speed camerasystem. A new iterative reconstruction algorithm with deflection angle compressedsensing revision is developed to improve the quality of reconstruction distributionfrom incomplete projection data. The algorithm, which combines the sparsity of theobject field gradientl1-norm, is adjusted by total variation with the steepest descentmethod. A compressed sensing weighting factor is employed in every iteration step tooptimize the reconstruction. In numerical simulation, the new approach producedreliable reconstruction for asymmetrical temperature distribution from6view-anglesprojections. The error analysis provided a good indication of the precision andconvergence of the algorithm. Compared with our previous algorithm for deflectiontomography, the new algorithm turned out to be more accurate. The maximum value error was reduced by27.03%and the normalized distance error was reduced by33.33%when the new reconstruction algorithm was employed.6view-anglesprojections of unsteady flow field is obtained by optical deflection tomographysampling system. In the experimental，the distribution of density and temperature forunsteady combustionare are reconstructed by the new reconstruction algorithm. Thenew reconstruction algorithm showed good performance in reconstruction of unsteadyflow field.