A-245 回転円柱後流の渦構造

概要

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Vorticity structures and flow field around a rotating circular cylinder at Reynolds numbers between (10)^2 and (10)^4 was numerically investigated. Velocity rate of the uniform velocity and the rotational velocity of the cylinder was changed from 0 to 3. In case of the potential flow around a rotating circular cylinder, upstream and downstream stagnation points come close with increase of the velocity ratio of α. Moreover, two stagnation points become a single point at α=2. In case of turbulent viscous flows, stagnation points also move and vorticity structures are dramatically change at high velocity ratio. At low velocity ratio, the wake has anti-symmetric vorticity structure and lift-drag ratio is rapidly increasing. However, when the velocity ratio exceeds 2,an absolute value of lift-drag ratio becomes small and alternative vorticity structure disappear. As a result, fluctuation of the aerodynamic forces turn weakness and the resulting aerodynamic sound becomes small. It reveals that moving surface or surface jet is effective for reduction of aerodynamic sound.
2003-07-28