AN ANALYTICAL MODEL FOR THE PREDICTION OF LIFT ON ROTATIONALLY OSCILLATING CYLINDER UNDER NO RESONANCE CONDITION WITH SOFT EXCITATION

An analytical model under the no resonance condition with soft excitation is developed to determine the lift on the rotationally oscillating circular cylinder in the lock-on regime. From numerical simulations of the flow field, lift coefficient data are obtained over a rotationally oscillating circular cylinder. Spectral analysis is applied to the data to characterize the non-linear coupling between the vortex shedding frequency and its third harmonic. From this analysis it is concluded that the forced Von der Pol equation should be used to model the lift coefficient on rotationally oscillating circular cylinder in the lock-on regime. Different forcing conditions have been shown to significantly affect the wake pattern and associated forces on the cylinder.