Abstract
A new technique of the frequency measurement, which is based on the digital image processing, has been developed for shedding vortices from a circular cylinder. The vortex motion behind a circular cylinder and the main flow motion in front of a circular cylinder are visualized by a dye injection method of fluorescent and a direct injection method of tracer particles. In the present technique, the shedding frequency of vortex and main flow velocity are both measured on the digital images. Visualized vortices in consecutive TV images are analyzed by Correlation Method and/or Density Averaging Method. The shedding frequency can be determined as the density pattern change caused by the, dyed vortices through a measurement region behind a circular cylinder. Using the present technique, St numbers at range of Re number 50 to 200 are measured automatically and quantitatively.
