Potential well escape via vortex-induced vibrations: A single-degree-of-freedom analysis

This paper presents approximate criteria that can be used to predict potential-well escape for a body undergoing vortex-induced vibrations. To this end, the method of harmonic balance is used to obtain an approximate analytical solution of the response assuming that the dynamics can be well described by adopting a single-degree-of-freedom reduced-order model. The escape phenomenon is investigated considering two flow conditions that are often encountered in engineering problems. The first occurs when the flow approaches the oscillator instantaneously at a set speed such that the transient dynamics of the oscillator are significant and can play an important role in determining the escape conditions. The second occurs when the speed of the flow approaching the body is quasi-statically increased such that the transient dynamics has a very little influence on the escape trajectories. In both scenarios, the dependence of the flow escape speed on the Strouhal number, the mass ratio between the flow and the oscillating body, and the shape of the potential well is resolved. The approximate analytical escape conditions are shown to be in good agreement with those obtained by numerically integrating the equations of motion.