DEVELOPMENT OF PIV MEASUREMENT SYSTEM FOR ELUCIDATING MICRO-MECHANISM OF FLOW

流场微观机理的研究在环境污染、化学反应、微重力装置、半导体、生物技术等研究中具有重要意义。我们小组一直致力于粒子图像测速仪(PIV)的发展，以阐明各种类型流动的详细结构。在本项目期间，取得了以下三个主要进展：Yamamoto提出了一种全新的PIV算法，该算法使用DelLaunay细分粒子跟踪方法、速度梯度张量粒子跟踪方法和基于模糊逻辑的粒子跟踪方法。通过对大变形流场的跟踪性修正，大大提高了计算速度。Ohta成功地测量了表面张力、湍流射流和颗粒流驱动的流动中的微尺度流动结构。通过与激光多普勒测速仪、同轴全息PIV的数据比较，评价了PIV的分辨率。Murai发展了PIV在多相流中的应用方法，并提出了高精度的粒子跟踪测速的后处理算法。PIV与后处理技术相结合，可以捕捉到泡状流中湍流的微观结构。

Investigation of micro-mechanism of flow fields becomes important in the research of environmental pollution, chemical reaction, micro-gravity devices, semiconductors, and biotechnology. Our group has been focussing on development of Particle Image Velocimetry (PIV) in order to elucidate the detailed structure of various type flows. In the period of the present project, three main advances have been achieved as follows.Yamamoto developed brand new algorithm for PIV using Dellaunay tesselation particle tracking method, velocity gradient tensor particle tracking method, and Fuzzy logic based particle tracking method. Computation speed is much improved with revision of trackability in highly deformed flow field. Ohta succeeded in measuring micro-scale flow structure in the flow driven by surface tension, turbulent jet flow, and particulate flow. Resolution of PIV is evaluated by comparing the data with Laser Doppler Velocimeter, In-line Holographic PIV.Murai developed the application method of PIV to multiphase flows, and highly accurate post-processing algorithm for Particle Tracking Velocimetry. Microscopic structure of turbulence in bubbly flow could be captured by combination of PIV and the post-processing.