通过突扩管的三维涡流

2018/12/11   下载量： 4 次

方案摘要

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应用领域 其他
检测样本 其他
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参考标准 暂无

采用双腔Gemini型PIV Nd:YAG 激光器系统做照明光源。532nm波长，200毫焦/脉冲输出能量。脉冲宽度5纳秒。测量部分采用4台LaVision Imager sCMOS高灵敏度相机。相机像素5百50万.进行水流通过突扩管的3D3C层析PIV流场测量。

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The jet flow past an abrupt expansion under some conditions switches intermittently between two states: quasi-axisymmetric expansion and gyroscopic-like precessing motion. In this work an experimental analysis is carried out by means of Tomographic Particle Image Velocimetry (Tomo-PIV).The self-excited flow precession generated by a 5:1 expansion of a round jet in a coaxial cylindrical chamber is investigated. The experiments are performed at a Reynolds number equal to 150,000. Proper Orthogonal Decomposition (POD) is applied to extract information on the organization of the larger structures of the precessing motion. This technique highlights the dominance of three modes: the first two are associated to the jet precession; the third one is representative of the axial motion. Furthermore, an approach based on the modal energy for the evaluation of the precession probability is presented. The application of a stability criterion shows that the self-induced swirl flow results to be unstable within the jet shear layer. The instability is responsible for the generation of helical-shaped vortices in the near field, instead of the expected phenomenology of the ring-vortices generation of circular jets.

上一篇 在一个双稳湍流涡旋火焰中，对间歇性动态的时间-频率定位
下一篇 采用偏振激光片状光源照明，实现双体积四脉冲层析PIV测量

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北京欧兰科技发展有限公司
金牌会员 丨 第17年
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