Induced vibrations of an hydrodynamic pendulum

We numerically study the movements of a cylinder subjected to the actions o f a hydrodynamic flow. The system mechanism simple by the low number of par ameters which characterize it, has only one degree of freedom. It can be an alysed like an oscillator undergoing a return force related to the vortex s hedding. The dominant frequency of oscillation of the pendulum is close to the frequency of emission, of the Von Karman street in the case of the moti onless cylinder The pendulum's oscillation amplitude, whatever the length l (b), is always close to the radius of the cylinder (A/D approximate to 0.5 for 3 < l(b) = 7). However; the vortex shedding patterns observed in the wa ke are very frequently different and related to the length l(b) for the Rey nolds number of 2000 imposed here. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.