Measurement of Three Dimensional Velocity Vectors in a Flow Field Based on a Spatio-Temporal Correlation Method

点击翻译按钮获取中文摘要

A measurement system of 3-D velocity vectors is essential in analyzing a highly complex flow field.In this study, a new measurement method of 3-D velocity vectors in a flow field using spatio-temporal correlation method was developed. It is an advanced method for 2-D velocity vector measurement using correlation. The method needs two travel particle images observed at a short distance in the flow direction. Each of the two images consists of frame time series. The 2-D information on a 3-D velocity vector can be obtained using spatial correlation. In addition, the temporal correlation gives information on the third dimension. A 3-D velocity vector is consequently obtained by calculating the spatio-temporal correlation between the two images. This system was actually applied to a simple 2-D flow and a 3-D flow with reverse flow to confirm the appropriateness of this technique and its measurement uncertainty was evaluated.In comparison with a conventional stereoscopic measurement method, in which each tracer is tracked in a 3-D space, the following advantages were clarified.1) The method has wide applications to visualized flow images because the images of tracer particles are observed as a spatial pattern.2) A spatially high-density vector distribution is obtained in a flow cross section.3) In principle, the method does not need any known information on the flow characteristics.The disadvantage, however, is that only a velocity vector distribution on a slit plane is obtained. To solve the problem, an improved optical system including slits will have to be devised to obtain many 3-D velocity vectors over the entire 3-D flow field.