Tomographic particle image velocimetry and its application to turbulent boundary layers
Tomographic particle image velocimetry and its application to turbulent boundary layers
复制标题
DOI：
--
复制
发表时间：
2008-06
期刊：
影响因子：
--
通讯作者：
G. Elsinga
中科院分区：
文献类型：
--
作者：
G. Elsinga
层析粒子图像测速技术是近年来发展起来的一种研究湍流三维运动的新的实验方法。该技术是标准PIV的扩展，并利用照明示踪粒子的几个同时视图和它们的三维重建作为光强度分布通过层析成像。然后通过3D互相关返回测量体积上的三分量速度矢量分布来分析重建的断层图像对。的层析成像算法的原理和细节进行了讨论，并进行了参数研究，以确定最重要的参数管理的实验设置，并显示其对重建精度的影响。在真实的实验条件下的技术的能力进行了评估与测量的湍流在近尾迹的圆柱。其次，将这种新技术应用于湍流边界层三维相干结构的研究。在低速湍流边界层和高雷诺数超声速边界层中，已经获得了单个（发夹）涡以及大尺度结构的定量可视化。高雷诺数数据还表明，一个非常大规模的流动组织不仅存在于流向，而且在展向方向。这些非常大尺度的运动似乎由大尺度的发夹状结构组成，它们在流向和展向方向上沿相对于流向的45度对角线沿着优先排列。此外，流场结构的时间演化是可视化的实验中，其中的Tomographic-PIV技术被施加到近时间分辨的图像序列记录在1.5 kHz。
Tomographic Particle Image Velocimetry is a new experimental method developed to study three-dimensional motion in turbulent flows. The technique is an extension of standard PIV and makes use of several simultaneous views of illuminated tracer particles and their three-dimensional reconstruction as a light intensity distribution by means of tomography. The reconstructed tomogram pair is then analyzed by means of 3D cross-correlation returning the three-component velocity vector distribution over the measurement volume. The principles and details of the tomographic algorithm are discussed and a parametric study is carried out by to identify the most important parameters governing the experimental setup and to show their effect on the reconstruction accuracy. The capability of the technique in real experimental conditions is assessed with the measurement of the turbulent flow in the near wake of a circular cylinder. Next, this new technique has been applied to study the three-dimensional coherent structures in turbulent boundary layers. Quantitative visualizations of the individual (hairpin) vortices as well as the large-scale structures in both a low speed turbulent boundary layer and a high Reynolds number supersonic boundary layer have been obtained. The high Reynolds number data also suggests a very-large-scale flow organization exists not only in streamwise direction but also in spanwise direction. These very-large scale motions appear to consist of large-scale hairpins, which display a preferential alignment in streamwise direction and in the spanwise direction along the 45 degrees diagonal with the respect to the streamwise direction. Moreover, the time evolution of the flow structures is visualized in an experiment, in which the Tomographic-PIV technique is applied to nearly time-resolved image sequences recorded at 1.5 kHz.