Abstract
A tuft in the air flow was observed by three CCD video cameras which were installed in the directions nearly perpendicular to each other. In this procedure, a tufted woolen yarn of the diameter of about 1 mm and of the length of 35 mm was attached on the top of a thin post pin.
Principle of this shape modelling is that the intersected zone which is constructed from multiple polygonal pyramids, every of which is bounded by the digitized cross sectional area in the picture image of the target and its lens center as a vertex results a polyhedron and becomes a good approximation to that shape if it is convex. This polyhedron is designed to construct a so-called solid model and is described with spatially fixed co-ordinates, so that not only its spatical shape, but also the position, direction, deformation or fluttering at the every moment are able to be estimated.
From the reconstructed shape modelling, influence of rigidness due to adhesives near the fixed end and a few millimeters of three dimensional displacement at the free end are observed. Free end moves like a cone of which vertex locates at the middle of the tuft.
This method is capable to serve for measurement and analysis of a single tuft characteristics depending on its material, kind of fluid or flow range. And also this has the posibility of quantitative analysis of three dimensional unsteady flow visualization.
