Research on Complex Turbulent Structure by Smart Visualized Information Processing Technique

本研究将智能可视化图像处理和小波技术应用于湍流图像和PIV （Particle image velocity metry）技术，以提高图像的时间分辨率和分析多尺度湍流结构。众所周知，流场图像在时域上是由一组顺序离散的图像组成的。智能可视化图像处理是一种基于亥姆霍兹方程将离散图像转换为连续图像的方法，在图像处理中具有较好的应用效果。本文采用湍流射流图像和标准PIV图像对智能可视化信息处理进行了评价。生成了具有较高时间分辨率的湍流尾迹图像，用于分析射流机理，生成的PIV图像得到的PIV结果与精确解吻合。可以说，智能可视化图像处理技术在流量分析和PIV系统中都是有效的。另一方面，应用矢量小波多分辨率技术对高分辨率双平面立体PIV系统的三维测量结果进行分析，揭示了湍流叶状射流近场多尺度涡旋结构的基本认识，将瞬时三维速度矢量分解为大、小尺度速度场。在叶状喷管的边缘位置周围可以清晰地观察到瞬时的大尺度流向涡对，并沿叶状喷管向外扩散。在叶片区域发现了较强的小尺度流向涡，它们首先沿叶片向外扩散，然后发展到整个测量流场。这些小尺度的流向涡在增强混合过程中也起着重要的作用。大尺度方位Kelvin-Helmholtz涡的强度大于流向涡的强度。下游较强的大尺度方位角涡集中在射流核心区域。少

This study developed an application of the smart visualized image processing and wavelet technique to turbulent flow images and PIV (Particle Image Velocimetry) technique in order to improve the temporal resolution of images and to analyze multi-scale turbulent structures. It is well-known fact that flow images consist of a set of sequentially discretized images in time domain. The smart visualized image processing can convert the discretized images into continuous images based on Helmholtz equation and is effective when it is used in image processing. In this study the turbulent jet images and standard PIV images were used to evaluate the smart visualized information processing. Images of a turbulent wake with higher temporal resolution were generated, which were used to analyze the mechanism of jet flow The PIV results obtained from the generated PIV images agreed with the accurate solution. It can say that the smart visualized image processing technique is effective in both flow ima … More ge analysis and PIV system. On the other hand, the vector wavelet multi-resolution technique was apply to analyzing the three-dimensional measurement results of a high-resolution dual-plane stereoscopic PIV system for revealing a fundamental understanding of the multi-scale vortical structures in the near field of turbulent lobed jet The instantaneous three-dimensional velocity vectors were decomposed into large-and small-scale velocity fields. The instantaneous pairs of large-scale streamwise vortices can be clearly observed around the edge position of the lobed nozzle and spread outward along the lobes. The stronger small-scale streamwise vortices were found in the lobe regions, which first spread outward along the lobes and then develop to the whole measured flow field. These small-scale streamwise vortices also play an important role in enhancing mixing process. It is also found that the strength of the large-scale azimuthal Kelvin-Helmholtz vortices is higher than that of the streamwise vortices. At the downstream the stronger large-scale azimuthal vortices are concentrated in the region of jet core. Less