Abstract
This paper describes the computer-aided image processing of a moiré pattern of vortices behind cylinders in steady flow.
Moiré topography has been paid attention as an effective way to visualize fluid phenomena, because three dimensional objects are recognized by this method.
But, in general, moiré fringes on fluid phenomena include many noises and the contrast of the image is weak because of the faint reflection of light on the surface of fluid.
Besides, when the moiré fringes are overlaped or tore off, it is necessary to modify these fringes.
For these reasons, it is difficult to get necessary informations in the moiré fringes on fluid phenomena by applying the usual image processing algorithm.
In order to solve these problems, we have developed a new algorithm for the computeraided automatic image processing of the moiré pattern.
This algorithm consists of a filter part and an analysis part.
In the filter part, the image contrast is emphasized, the noises are excluded, and the lack of fringes is corrected.
In the analysis part, the center lines of fringes and the center points of vortices are picked out and the fringe numbers are determined.
In this paper, we explain the principle of this algorithm and show the results of its application to some moiré patterns of vortices behind cylinders in steady flow.
