A Technique to Measure the Flow Velocity by an Analysis of Tracer Pathline Images : 3rd Report : Three-dimensional Velocity Measurement by Use of the Correlation Method

Abstract

Tracer pathline images of flow field give us a great deal of information about the flow field, and several methods were developed to obtain the velocity vectors from these pictures. However, the techniques mainly give us 2-dimensional velocity components because they use a 2-dimensional slit light sheet to observe the flow field. In this paper, a new technique is proposed to obtain the 3-dimensional velocity components from a pair of stereoscopic photographs of the flow field which is lighted by slightly thick slit light sheet. The summary is as follows. 1) The new technique was formed by combining the stereoscopic photograph with the correlation method. 2) The technique makes it easy to analyse the stereoscopic photograph which contains highly dense particles. 3) The technique is applied to measure the 3-dimensional velocity components of the flow field around a circular cylinder in the uniform flow and reasonable results are obtained.