Visualization and Measuement of Rarefied Gas Flow using LIUFV

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Flow field of rarefied gas flow can be visualized by LIUVF(Laser-Induced Ultra Violet Fluorescence) of oxygen molecules using an image intensifier and a CCD camera. ArF excimer laser at 193 nm corresponds to the Schumen -Runge X*B system of transitions. Oxygen molecules radiate the UV fluorescence by irradiation of this laser beam. The LIUVF method is applied to the flow visualization of the rarefied gas flow; a supersonic free jet. Because of weakness of the fluorescence, however, an image of the flow field can not be obtained less clearly using the fluorescence of oxygen molecules than that of iodine molecules. For temperature measurement of the rarefied gas flow, the results also indicates low accuracy. We believe that it is necessary to improve a detection system of the fluorescence.Flow visualization and temperature measurement of the rarefied gas flow using laser-induced iodine fluorescence is also carried out. The flow visualization is applied to an analysis of the flow field structure of the opposed supersonic free jets. Characteristic structures of the flow field and an unstable flow in the interacting region is found. For temperature measurement, two lines PLIF method is developed. A method for selection of optimum combination of a two absorption lines is proposed theoretically and the propriety and effectiveness is verified by experiments