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CHARACTERISTICS OF FLOW OVER A CIRCULAR CYLINDER AT Red=140,000

Hyunsik Kim
School of Mechanical and Aerospace Engineering, Seoul National University Seoul 151-744, Korea

Jungil Lee
School of Mechanical and Aerospace Engineering, Seoul National University Seoul 151-744, Korea

Jooha Kim
School of Mechanical and Aerospace Engineering, Seoul National University Seoul 151-744, Korea

Haecheon Choi
Department of Mechanical & Aerospace Engineering Seoul National University 1, Gwanak-ro, Gwanak-gu, Seoul 08826, Korea

Résumé

In the present study, we conduct both numerical and experimental studies to investigate the characteristics of flow over a circular cylinder at Red = 140,000, where Red is the Reynolds number based on the cylinder diameter d and free-stream velocity. Large eddy simulation (LES) is conducted for numerical investigation, and direct force and particle image velocimetry (PIV) measurements are conducted for experimental investigation. The drag and base pressure coefficients from present numerical and experimental studies agree well with each other. The instantaneous flow over a circular cylinder exhibits various flow structures such as laminar separation at the cylinder surface, shear-layer after the separation, vivid small-scale vortices and vortex shedding in the wake. In the near wake of circular cylinder, it is observed that a vortical structure distorted in spanwise direction and weak vortex shedding intermittently occurs, inducing relatively low drag and lift fluctuations.