Affiliations: [a] Department of Mechanical Engineering, Kagoshima
University, 1-21-40, Korimoto, Kagoshima 890-0065, Japan. Tel.: +81 99 285
8252; Fax: +81 99 250 3181; E-mail: [email protected]
| [b] Department of Mechanical Engineering, The Hong Kong
Polytechnic University, Hung Hom, Kowloon, Hong Kong, China. Tel.: +852 2766
6662; Fax: +852 2365 4703; E-mail: [email protected]
| [c] Department of Mechanical Engineering, Nihon
University, 1-8-14, Kanda Surugadai, Chiyoda-ku, Tokyo 101, Japan. Tel.: +81 3
3259 0749; Fax: +81 3 3293 8254; E-mail: [email protected]
| [d] Department of Electrical & Electonic Engineering,
Hosei University, 3-7-2, Kajino, Koganei, Tokyo 184, Japan. Tel.: +81 42 387
6200; Fax: +81 42 387 6200; E-mail: [email protected]
| [e] Shirayuri Women's College 1-25, Modorigaoka,
Chofu-shi, Tokyo 182, Japan. Tel.: +81 3 3326 7604; Fax: +81 3 3793 7461;
E-mail: [email protected]
Abstract: The vector wavelet multi-resolution technique based on the
orthogonal wavelet transform was used to analyze the velocity vector data that
were simultaneously obtained by sixteen X-wires in the turbulent near-wake of a
circular cylinder at different streamwise positions. The instantaneous velocity
vector field is decomposed into the multi-scale structures, and its sectional
streamline of various scales is displayed. The large-scale structures in the
plane of mean shear are consistent with the well-known Kármán vortices. The
structures that correspond to the saddle region between Kármán vortices are
identified with the rib-like structures. Even smaller scale structures are also
observed. As increasing x/d, the decay of vortical structure
and rib-like structure are observed. The topologies of Reynolds stress and RMS
vorticity associated with the multi-scale structures are discussed at different
downstream positions. It is found that the most significant contribution to
Reynolds stress comes from the frequency components of f ≤
219 Hz at x/d = 20. However, the contribution to
Reynolds stress coming from the intermediate-scale structure becomes weak at
x/d = 40. The RMS vorticity components of f =
875 Hz is the largest among all components.
