Affiliations: School of Mechanical and Aerospace Engineering, Seoul
National University, Seoul 151-742, Korea. E-mail: jyyoo@plaza.snu.ac.kr | School of Mechanical and Automotive Engineering,
Sunchon National University, Jeonnam 540-742, Korea | Department of Mechanical Engineering, Seoul National
University of Technology, Seoul 139-743, Korea
Abstract: A high-definition analysis based on flow topology is made on the
vortex motions under natural and lock-on conditions in the near-wake region of
a circular cylinder, where two-dimensional flow fields in the wake-transition
regime are measured by a time-resolved PIV system. The Reynolds stress
distributions are examined in view of the mean separation streamline and the
trajectory of the vortex center. It is shown that, by the lock-on, the Reynolds
stresses become stronger and their dispositions match well with the shortened
wake bubble, indicating perfect synchronization of shedding to the oscillatory
forcing flow in the near field, which causes increased lift and drag
forces.
Keywords: Time-Resolved PIV, Trajectory of Vortex Center, Wake Bubble, Lock-on
