Development of measurement method for investigating three dimensional turbulence structures in liquid-slid flow

本研究的目的是发展一种测量技术，以了解液固流动中的三维湍流结构。本研究由两个过程组成；一个是对武原研发的超分辨率PIV在时间分辨率上的改进，另一个是对渡边研发的三维立体PIV在空间分辨率上的改进。超分辨率PIV虽然可以通过使用多种粒子示踪剂实现高空间分辨率的流场测量，但由于没有足够的捕获系统，其时间分辨率不够。在该科研基金的大力帮助下，购买了高分辨率、宽范围的高速视频系统，解决了这一问题。利用该高速视频系统，采集了多孔体内部及附近流场的图像。详细研究了多孔体内部及下游区域湍流的产生和衰减机理。虽然三维立体PIV可以测量流体的三维流动结构，但如果在流体中添加了许多粒子示踪剂，则需要投入大量的时间来分析。通过改进计算算法，克服了这一问题。将三维立体PIV重构为具有高空间分辨率的PIV系统。将改进的3- d立体PIV应用于破碎区下的多相流。研究表明，改进的三维立体PIV是测量破碎波作用下复杂流体流动和泥沙运动的有效工具。此外，还提出了一种新的图像测速方法，即“路径线连接测速法”，用于测量具有高速流体运动和强湍流的三维结构的液固流动。将“路径线连接测速法”应用于粒子运动引起的流场测量。结果表明，连接速度计的路径线是测量含高浓度颗粒和水面的多相流的一种非常有用的工具。少

The aim of this study is to develop a measurement technique for understanding three dimensional turbulence structures in liquid-solid flows. This study is composed of two processes ; one is for improvement of Super Resolution PIV developed by Takehara on time resolution and the other is for improvement of 3-D stereo PIV developed by Watanabe on space resolution.Although the super resolution PIV can measure the flow field with high space resolution by using many particle tracers for visualization, it did not have enough time resolution because we did not have enough capturing system. This problem was overcome by purchasing a high-speed video system with high resolution and wide range with great help of this scientific research fund. By using this high-speed video system the images of flow fields inside and in the vicinity of a porous body were captured. And generation and decay mechanisms of turbulence flow inside the porous body and in the downstream region have been studied in detail. … More Although the 3-D stereo PIV can measure the three dimensional flow structures, it needed a great investment of time to analyze if many particle tracers were seeded in fluid. This problem was overcome by improving calculation algorism. As a result the 3-D stereo PIV was reconstructed as a PIV system with high space resolution. The improved 3-Dstereo PIV was applied to a multi-phase flow under the breaking zone. It has been found that the improved 3-D stereo PIV is a useful tool for measurement of complex fluid flow and sediment motion under breaking waves.Furthermore, a new image velocimetry, called "path line connecting velocimetry", has been developed for measurement of the liquid-solid flows with high speed fluid motion and strong turbulence with three dimensional structure. The "path line connecting velocimetry" has been applied to the measurement of the flow field induced by particle motion. As a result, it was shown that the path line connecting velocimetry is a very useful tool for measurement of multi-phase flows including particles with high concentration and water surface. Less