レーザ誘起蛍光法とシュリーレン法による超音速キャビティ振動流れの可視化

概要

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The oscillatory behaviors in a supersonic cavity flow are visualized by LIF (Laser-Induced Fluorescence) and schlieren methods. In the LIF method, an argon-ion laser is used as a light source to excite the iodine molecules seeded into the working gas. The iodine fluorescence, whose intensity is known to be a function of temperature, is detected by the photomultiplier. The pressure oscillation on the bottom wall of the cavity is also measured simultaneously with the fluorescence detection. The phase of fluorescence-intensity oscillation is corrected on the basis of the cavity-bottom pressure oscillation and the correction is performed at every fluorescence detection point. As a result, the temperature oscillations inside and outside the cavity are qualitatively visualized in two-dimensional sense. In the schlieren method, the light source is controlled so as to flash responding to a specific phase of the periodic pressure signal and the oscillatory motion of the shear layer developing along the cavity span is captured. By carefully observing both of the visualization results, the relation between the temperature oscillation and shear-layer motion is clarified.