The Research For Three-dimensional Reconstruction Of Fluid Field Based On Infrared Schlieren Tomography Technique

At present, schlieren technique is a classical optical method to the display andmeasurement of plume flow field, which is widely used for observing the airflowboundary layer, shock wave, combustion, the gas within the hot and cold convection,the heat and mass transfer, wind tunnel experiment and so on, this method is a opticaltesting technology of plume flow field.In this paper, basic principles and methods of infrared schlieren techniques andtraditional schlieren technology are first introduced. Then, this paper summarizessynthetically the applications of infrared schlieren techniques and traditional schlierentechnology in the combustion, heat and mass transfer, shock wave and wind tunneltests field etc. The advantages and disadvantages of infrared schlieren are analyzed too.Using infrared schlieren chromatography technique to analyze three-dimensionalreconstruction of the fluid field is put forward.In order to achieve the reconstructions of the refractive index and temperaturefields, there were nonexistent image of the distribution of fluid field and existent imageof the distribution of fluid field obtained through the experiment shooting. The imageswhich were not in the same time but the same position were carried outcross-correlation analysis by Matlab image processing software to obtain the matchingposition and offset of two images and the deflection angle of light on infrared CCD.The deflection angles of light passing over fluid field were used to reconstruct index ofrefraction from inverse Radon transform. Then the Gladstone-Dale relation and theIdea-Gas Equation were used to solve, and using algebraic reconstruction techniqueobtain the distribution of temperature field to the section. The experiment resultsshowed that using infrared schlieren technology improved greatly the accuracy of theirreconstructions. Comparing with the previous experimental results inferred thedistributions of refractive index and temperature field in line with the actual situation.Finally, in this paper, using fluent software conducted numerical simulation aboutplume fluid field of rocket engine nozzle. Fluid field was analyzed to the distributionsof temperature，pressure，density and mass fraction of various gases. According tonumerical simulation, obtained the distributions of density and mass fraction of variousgases and Gladstone-Dale relation calculated the distribution of index of refraction. At last, comparing simulation results with experiment results and simultaneously dataerror was analyzed and the reason why error happened.