Part I. 3DPTV: Advances and error analysis. Part II. Extension of Guderley's solution for converging shock waves
Part I. 3DPTV: Advances and error analysis. Part II. Extension of Guderley's solution for converging shock waves
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第一部分：3DPTV：进展和错误分析。
DOI：
10.7907/09zh-9m66
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
N. Ponchaut
中科院分区：
文献类型：
--
作者：
N. Ponchaut
这项工作分为两个不相关的部分。在第一部分中，开发并测试了一个完整的三维粒子跟踪系统。三个图像，从三个独立的CCD放置在一个等边三角形的顶点，允许通过三角测量来确定粒子的三维位置。在两个不同时间测量的颗粒位置然后可以用于创建三分量三维速度场。关键的发展是准确处理重叠颗粒图像的能力、偏移CCD以显着提高有效分辨率的能力、暗淡颗粒图像的处理以及在只有两组图像存在时非常适合三维流动的混合颗粒跟踪技术。进行了深入的理论误差分析，给出了误差的重要来源及其对整个系统的影响。通过一系列实验验证了误差分析，并进行了涡流测量。
在第二部分中，研究了初始静止流中圆柱形或球形内爆和反射激波的问题。Guderley在原点附近的强激波解通过在入射激波和反射激波的级数展开解中增加两项而得到改进。对于激波离原点还很远的情况，我们也构造了一个级数展开式。此外，还编写了基于特征线法的程序。由于变量的适当变化，激波运动可以从几乎无穷大到非常接近反射点计算。级数展开，特征程序，并使用欧拉求解器得到的结果之间进行了比较。这些比较表明，在Guderley解中加入两项显著提高了级数展开的精度。
This work is divided into two unrelated parts. In the first part, a full three-dimensional particle tracking system was developed and tested. Three images, from three separate CCDs placed at the vertices of an equilateral triangle, permit the three-dimensional location of particles to be determined by triangulation. Particle locations measured at two different times can then be used to create a three-component, three-dimensional velocity field. Key developments are the ability to accurately process overlapping particle images, offset CCDs to significantly improve effective resolution, treatment of dim particle images, and a hybrid particle tracking technique ideal for three-dimensional flows when only two sets of images exist. An in-depth theoretical error analysis was performed, which gives the important sources of error and their effect on the overall system. This error analysis was verified through a series of experiments, and a vortex flow measurement was performed.
In the second part, the problem of a cylindrically or spherically imploding and reflecting shock wave in a flow initially at rest was examined. Guderley's strong shock solution around the origin was improved by adding two more terms in the series expansion solution for both the incoming and the reflected shock waves. A series expansion was also constructed for the case where the shock is still very far from the origin. In addition, a program based on the characteristics method was written. Thanks to an appropriate change of variables, the shock motion could be computed from virtually infinity to very close to the reflection point. Comparisons were made between the series expansions, the characteristics program, and the results obtained using an Euler solver. These comparisons showed that the addition of two terms to the Guderley solution significantly increases the accuracy of the series expansion.