Vortex shedding from a circular cylinder in oscillatory flow

Vortex shedding from a cylinder in oscillatory flows has been investigated by measuring the skin friction on the cylinder surface, the lift and drag forces, and the wake velocity and then deducing the power spectrum of these fluctuating quantities. Lift and drag variations below and in the locking-on regime are discussed. In particular, it is shown that the lift oscillates, both in stationary and oscillatory flows, at the frequency of vortex shedding with high amplitude in steady flow and in the locking-on regime. The drag oscillates at a frequency that is twice the shedding frequency in stationary flows; it oscillates at the frequency of oscillatory flow even in the locking-on regime where a strong second harmonic appears.