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首页> 外文期刊>Aerospace science and technology >A comparison of PIV and interferometric Rayleigh scattering measurements in the near field of underexpanded sonic jets
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A comparison of PIV and interferometric Rayleigh scattering measurements in the near field of underexpanded sonic jets

机译：欠扩张声速射流近场中PIV和干涉瑞利散射测量的比较

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Velocity measurements were made in the near field of underexpanded sonic air jets using particle image velocimetry (Ply), interferometric Rayleigh scattering and total pressure tubes. Shadowgraph technique was also used to visualize the shock waves generated due to underexpansion in the near field of the jets. The two main objectives were to study the effect of underexpansion ratio on the flow structure and to determine the suitability of the PIV technique in high-speed flows with shock waves. The jets were produced by a convergent nozzle connected to a settling chamber. Different underexpansion conditions were obtained by changing the chamber (jet total) pressure against the atmospheric ambient. Jet exit-to ambient pressure ratios ranged between 1 and 20.32 corresponding to fully-expanded jet Mach numbers between 1 and 3.03, respectively. The PIV measurements of the streamwise and transverse velocities in the near field up to ten nozzle diameters were made, from which distributions of mean velocities, turbulence intensities and turbulent shear stress were obtained. In order to check the accuracy of the PIV measurements (particularly, the particle lag effects) an interferometric Rayleigh scattering technique was also used to obtain the streamwise velocity for certain jet conditions. Additionally, some pressure measurements were made using a total pressure tube to provide a comparison with the two optical techniques. In general, the PIV method provided good velocity data in the jet near field and allowed the identification of flow structures and their respective locations such as shock waves, expansion regions, slip lines and shear layers. However, when compared to the Rayleigh scattering data, the effect of particle inertia was evident in certain locations in the jets. This effect was most dramatic just downstream of the Mach disk (barrel shock) in the case of highly underexpanded jets. (C) 2017 Elsevier Masson SAS. All rights reserved.
机译：使用粒子图像测速仪（Ply），干涉瑞利散射和总压管在膨胀不足的声速喷气机的近场中进行速度测量。阴影图技术还用于可视化由于射流近场扩展不足而产生的冲击波。两个主要目标是研究膨胀率不足对流动结构的影响，并确定PIV技术在具有冲击波的高速流动中的适用性。射流由连接到沉降室的收敛喷嘴产生。通过相对于大气环境改变腔室（喷射总压力）来获得不同的膨胀不足条件。射流出口与环境压力之比在1和20.32之间，分别对应于在1和3.03之间的完全膨胀射流马赫数。进行了近场中至十个喷嘴直径的流向和横向速度的PIV测量，由此获得了平均速度，湍流强度和湍流剪切应力的分布。为了检查PIV测量的准确性（特别是颗粒滞后效应），还使用干涉瑞利散射技术来获得某些喷射条件下的流向速度。另外，使用总压力管进行了一些压力测量，以与两种光学技术进行比较。通常，PIV方法在射流近场中提供了良好的速度数据，并允许识别流动结构及其各自的位置，例如冲击波，膨胀区域，滑移线和剪切层。但是，当与瑞利散射数据进行比较时，粒子惯性的影响在射流中的某些位置很明显。在喷头高度不足的情况下，这种影响在马赫盘的下游（桶形冲击）最为明显。 （C）2017 Elsevier Masson SAS。版权所有。

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