Forma, Vol. 7 (No. 3), pp. 235-247, 1992
Original Paper

Can we educe vortices from a single dye picture?

Takayuki Sato, Yoshitaka Kakizaki and Ryuji Takaki

Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183, Japan

(Received July 24, 1990; Accepted January 19, 1993)

Keywords: Vortex, Mixing layer, Streakline, Image processing, Dye picture

Abstract. Vortex streets in the two-dimensional mixing layer were visualized by dye injection at the splitter plate, and their photographs were analysed by the use of an image processing system in order to examine a possibility to educe vortices based upon certain algorithm. Each dye lump in the photographs were examined to judge whether it was a vortex or not according to criterions based on past studies on the mixing layer. The results of judgement were compared with those of velocity measurement by laser velocimeter and spectrum analyser. They showed good agreement especially for the case where the mixing layer was excited artificially (a regular vortex street is known to appear in this case).