Three dimensional and temporal measurement of temperature field in a heating jet by tomographic laser interferometry

The paper describes a three dimensional and time resolved temperature measurement technique for a gaseous flow and its application to a heating jet. For the whole field investigation, computed tomography is one of the significant techniques to make an internal structure clear and to understand the distribution of physical properties of flow fields. Conventional CT method, however, has difficulty in measuring the unsteady flow or turbulence due to the time consuming rotation of the projecting equipment. The objective of the present study is to develop the optical tomography technique with quad Twyman-Green interferometer in order to obtain the multiple finite fringe images from different directions simultaneously. In spite of the smaller number of projections, three dimensional temperature distribution of a heating gaseous jet from a rectangle nozzle was successfully reconstructed by the iterative calculation technique with a physical constraint for temperature. The technique was compared with the reliable thermocouple method on the steady jet and both measured results agreed quite well. The technique was further applied to the measurement of a periodic forced jet and obtained the instantaneous temperature field and their temporal fluctuation successfully.