Laminar flow past a rotating circular cylinder

The present study numerically investigates two-dimensional laminar flow pas t a circular cylinder rotating with a constant angular velocity, for the pu rpose of controlling vortex shedding and understanding the underlying flow mechanism. Numerical simulations are performed for flows with Re=60, 100, a nd 160 in the range of 0 less than or equal to alpha less than or equal to 2.5, where alpha is the circumferential speed at the cylinder surface norma lized by the free-stream velocity. Results show that the rotation of a cyli nder can suppress vortex shedding effectively. Vortex shedding exists at lo w rotational speeds and completely disappears at alpha >alpha(L), where alp ha(L) is the critical rotational speed which shows a logarithmic dependence on Re. The Strouhal number remains nearly constant regardless of alpha whi le vortex shedding exists. With increasing alpha, the mean lift increases l inearly and the mean drag decreases, which differ significantly from those predicted by the potential flow theory. On the other hand, the amplitude of lift fluctuation stays nearly constant with increasing alpha (<alpha(L)), while that of drag fluctuation increases. Further studies from the instanta neous flow fields demonstrate again that the rotation of a cylinder makes a substantial effect on the flow pattern. (C) 1999 American Institute of Phy sics. [S1070-6631(99)01211-8].