Instantaneous pressure and material acceleration measurements using a four-exposure PIV system
Instantaneous pressure and material acceleration measurements using a four-exposure PIV system
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DOI：
10.1007/s00348-006-0152-7
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发表时间：
2006-08-01
影响因子：
2.4
通讯作者：
Katz, Joseph
中科院分区：
文献类型：
--
作者：
Liu, Xiaofeng;Katz, Joseph
本文介绍了一种非侵入式技术，用于测量流场中一个样本区域上的瞬时空间压力分布。采用四曝光粒子图像测速（PIV）系统，通过比较同一组粒子在不同时刻的速度来测量物质加速度的分布，然后对其进行积分以获得压力分布。同时将两个相机暴露于相同的粒子场，并对图像进行互相关处理，能够使两个视场精确匹配。对两个相机所测速度矢量应用局部图像变形校正，可将合成图像中因相对错位和图像失真导致的误差降低至约0.01像素。引入一种全方位虚拟边界积分方案来对加速度进行积分，同时将加速度局部随机误差的影响降至最低。通过迭代沿边界校正压力可实现进一步的改进。通常3 - 5次迭代足以将每次迭代中平均压力增量的变化降低至小于动压的0.1%。利用旋转流和驻点流的合成图像对该技术原理进行的验证测试表明，测量压力与精确值的标准偏差约为1.0%。该系统用于测量二维空腔湍流场的瞬时压力和加速度分布，并给出了示例结果。
This paper describes a non-intrusive technique for measuring the instantaneous spatial pressure distribution over a sample area in a flow field. A four-exposure PIV system is used for measuring the distribution of material acceleration by comparing the velocity of the same group of particles at different times and then integrating it to obtain the pressure distribution. Exposing both cameras to the same particle field at the same time and cross-correlating the images enables precision matching of the two fields of view. Application of local image deformation correction to velocity vectors measured by the two cameras reduces the error due to relative misalignment and image distortion to about 0.01 pixels in synthetic images. An omni-directional virtual boundary integration scheme is introduced to integrate the acceleration while minimizing the effect of the local random errors in acceleration. Further improvements are achieved by iterations to correct the pressure along the boundary. Typically 3-5 iterations are sufficient for reducing the incremental mean pressure change in each iteration to less than 0.1% of the dynamic pressure. Validation tests of the principles of the technique using synthetic images of rotating and stagnation point flows show that the standard deviation of the measured pressure from the exact value is about 1.0%. This system is used to measure the instantaneous pressure and acceleration distributions of a 2D cavity turbulent flow field and sample results are presented.