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Journal of Flow Visualization and Image Processing
SJR: 0.161 SNIP: 0.312 CiteScore™: 0.1

ISSN Imprimir: 1065-3090
ISSN En Línea: 1940-4336

Journal of Flow Visualization and Image Processing

DOI: 10.1615/JFlowVisImageProc.v5.i2.20
pages 105-113

MEASUREMENT OF THE EVOLVING LARGE EDDIES IN AXISYMMETRIC JETS FROM TRAVERSING CAMERA BY USING THE CROSS-CORRELATION TECHNIQUE

Kenichi Kobayashi
Meiji University, Higashimita 1-1-1, Tama-ku, Kawasaki 214-8571, Japan
Kazuyuki Morishita
Department of Mechanical Engineering and Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
Yuzo Kato
Department of Mechanical Engineering, Kobe University, Kobe, Hyogo, Japan
Hideo Yoshida
Dept. of Aeronautics and Astronautics, Kyoto University, Nishikyo-ku, Kyoto, 615-8540, Japan
Ryozo Echigo
Department of Mechanical Engineering and Science, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan

SINOPSIS

To investigate the evolving process of the large structures in turbulence, an image-processing technique with a camera traversing at mean axial flow velocity was developed and applied to vortex rings and axisymmetric jets. In order to obtain the complete velocity profiles in one run, the traversing unit for a CCD camera was controlled by a personal computer to synchronize the traversing rate and the eddy motion. Video signals from the CCD camera were recorded continuously by a VCR with two binary bar codes: one to identify the video field, and the other to specify the camera position and the traversing rate. The cross-correlation technique was employed to obtain two-dimensional velocity distributions from the recorded images. From successive maps of instantaneous velocity and vorticity distributions, the motion of large eddies (vortex pairing, entrainment) that cannot be measured quantitatively by conventional techniques can be dynamically revealed using a traversing camera.