The Development of a Multi-dimensional Image Processing System for Complex Flow Field Diagnostics

本文对高精度复杂流场诊断的多维图像处理技术的发展进行了广泛的研究。同时测量流体流动中的矢量（速度）场和标量（香料浓度和/或温度）场的先进技术也得到了发展。利用这些先进的技术，构建了高精度复杂流场诊断的多维图像处理系统——开发了多维图像处理系统的专用软件，从采集的图像中高精度地提取复杂的多维信息。利用人工可视化图像，对各种粒子图像测速（PIV）和粒子跟踪测速（PTV）图像处理算法进行了评价，并提出了提高湍流测量精度的优化方法。多维图像处理系统的硬件包括高功率双脉冲Nd: YAG激光器、高分辨率互相关CCD相机、高性能的主机和超大容量的全场、时变和高空间分辨率数字图像采集和处理。PIV和激光诱导荧光（LIF）技术可同时进行矢量（速度）和标量（温度和/或香料浓度）场的流体流动测量。利用多维图像处理系统，研究了矩形槽内的自激晃动现象。通过将本系统的测量结果与LDV（激光多普勒速度）测量数据进行比较，评价了多维图像处理系统的整体系统性能和精度水平，认为具有很高的精度水平。基于本系统对叶状射流混合流和圆形射流混合流的测量结果，定量地可视化了射流混合流中各种湍流和垂直结构的演变过程。分析了叶状喷嘴较常规圆形喷嘴增强混合的机理。这也证明了该系统在复杂流体诊断中的广泛可行性。在与计算流体动力学（CFD）方法的配合下，本系统还可以进一步发展为用于复杂流动诊断的混合系统，这被认为是未来流体动力学诊断系统的发展方向。少

Extensive investigations about multi-dimensional image processing technique development for complex flow field diagnostics with high accuracy had been conducted in the pres8nt study. Advanced techniques for the simultaneous measurement of the vector (velocity) fields and scalar (spices concentration and/or temperature) fields in fluid flows had also been developed. Taking the advantage of these advanced techniques, a multi-dimensional image processing system for complex flow field diagnostics with high accuracy had been constructed- The specialized software for the multi-dimensional image processing system to do complicated multi-dimensional information extraction with high accuracy from the acquiring images had been developed. By using the artificial visualization images, various Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) image processing algorithms had been evaluated, and optimized methods for turbulence flow measurement accuracy improved had also been 1 … More 3uggested. The hardware of the multi-dimensional image processing system includes high-power double-pulsed Nd : YAG Lasers, high resolution cross-correlation CCD cameras, excellent-performanced host computer arid colossal memory for the whole-field, time-dependent and high spatial-resolved digital image acquiring and processing. Both PIV and Laser Induced Fluorescence (LIF) techniques were used to conduct simultaneous vector (velocity) and scalar (temperature and/or spices concentration) fields measurement of fluid flows.By using the multi-dimensional image processing system, a self-induced sloshing phenomena in a rectangular tank was investigated. The whole system performance and accuracy level of the multi-dimensional image processing system was evaluated through the comparison of the measurement results of the present system with the LDV (Laser Doppler Velocimenty) measurement data, which Were considered to have very high accuracy level. Based oh the measurement results of the present system to a lobed jet mixing flow and a circular jet flow, the evolution processes of various turbulent and vertical structures in the jet mixing flows were visualized quantitatively. The mechanism of the mixing enhancement of lobed nozzles over conventional circular nozzles was also analyzed. Which also demonstrated the versatile feasibility of the present system for complex flow diagnostics.In cooperation with computational Fluid Dynamics (CFD) methods, the present system may also be further developed into a hybrid system for complex flow diagnostics, which is considered to be the fashion of future fluid dynamics diagnostic system. Less