Abstract
Vorticity structures and flow field around a rotating circular cylinder at Reynolds numbers between 102 and 104 was numerically visualized. Velocity ratio of the uniform velocity and the rotational velocity of the cylinder was changed from 0 to 3. At low velocity ratio, the wake has anti-symmetric vorticity structure and lift-drag ratio is rapidly increasing. However, when the velocity ratio exceeds about 2, an absolute value of lift-drag ratio becomes small and alternative vorticity structure disappears. As a result, fluctuation of the aerodynamic forces turn weakness and the resulting aerodynamic sound becomes small. Source term of aerodynamic sound was also visualized by using results of CFD analysis. Sound source term generated large scale eddies disappeared at high velocity ratio. It reveals that rotating cylinders are effective for reduction of aerodynamic sound.
