Abstract A single-pixel ensemble correlation method was applied to the schlieren and shadowgraph image velocimetry (SIV) and a velocimetry method that can obtain the convection velocity distribution of high spatial resolution without an expensive pulsed laser system being achieved for a laboratory-scale supersonic jet flow. A cold axisymmetric supersonic jet was employed, and the basic characteristics of the convection velocity fields are measured by SIV as well as those of the velocity fields by the particle image velocimetry (PIV) in the single-pixel resolution. The Mach number of a supersonic jet was 2.0, and the Reynolds number based on the diameter of the nozzle exit was 1.0 × 10 6 . A pulsed light-emitting-diode light source was used for SIV as a less expensive light source. The single-pixel ensemble correlation method applied to PIV clearly visualizes the potential core and the shear layer development with the high spatial resolution. The axial velocity of SIV at the jet centerline is approximately 0.7–0.8 times of that of PIV which seems to relate to the convection velocity. The velocity calculated from the shadowgraph images agrees well with the convection velocity estimated from the Mach wave emission angle. The comparison between the scale of the visualized turbulent structure and the length scale of large eddies implied that the quantitative discussion of the SIV measurement requires careful consideration of the scale of the visualized turbulent structure on the SIV image. Graphic abstract

中文翻译：

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通过粒子/纹影图像测速法测量的超音速射流的单像素分辨率速度/对流速度场

摘要 将单像素系综相关方法应用于纹影图像测速 (SIV) 和测速方法，无需昂贵的脉冲激光系统即可获得高空间分辨率的对流速度分布，用于实验室规模的超音速喷流。流。采用冷轴对称超音速射流，对流速度场的基本特征由SIV测量，速度场的基本特征由粒子图像测速（PIV）以单像素分辨率测量。超音速射流的马赫数为2.0，基于喷嘴出口直径的雷诺数为1.0×10 6 。SIV 使用脉冲发光二极管光源作为较便宜的光源。应用于 PIV 的单像素集合相关方法以高空间分辨率清楚地显示了潜在的核心和剪切层的发展。SIV 在射流中心线的轴向速度大约是 PIV 的 0.7-0.8 倍，这似乎与对流速度有关。从阴影图图像计算出的速度与根据马赫波发射角估计的对流速度非常吻合。可视化湍流结构尺度与大涡流长度尺度之间的比较表明，对 SIV 测量的定量讨论需要仔细考虑 SIV 图像上可视化湍流结构的尺度。图形摘要 SIV 在射流中心线的轴向速度大约是 PIV 的 0.7-0.8 倍，这似乎与对流速度有关。从阴影图图像计算出的速度与根据马赫波发射角估计的对流速度非常吻合。可视化湍流结构尺度与大涡流长度尺度之间的比较表明，对 SIV 测量的定量讨论需要仔细考虑 SIV 图像上可视化湍流结构的尺度。图形摘要 SIV 在射流中心线的轴向速度大约是 PIV 的 0.7-0.8 倍，这似乎与对流速度有关。从阴影图图像计算出的速度与根据马赫波发射角估计的对流速度非常吻合。可视化湍流结构尺度与大涡流长度尺度之间的比较表明，对 SIV 测量的定量讨论需要仔细考虑 SIV 图像上可视化湍流结构的尺度。图形摘要 可视化湍流结构尺度与大涡流长度尺度之间的比较表明，对 SIV 测量的定量讨论需要仔细考虑 SIV 图像上可视化湍流结构的尺度。图形摘要 可视化湍流结构尺度与大涡流长度尺度之间的比较表明，对 SIV 测量的定量讨论需要仔细考虑 SIV 图像上可视化湍流结构的尺度。图形摘要