Lock-in behavior in simulated vortex-induced vibration

Results are presented for a two-dimensional numerical simulation of vortex-induced vibration of a circular cylinder at a Reynolds number of 250. A spectral element spatial discretization and a stiffly stable time integration scheme were employed to solve the Navier-Stokes equations in an accelerating frame of reference attached to the cylinder. The response envelope of the vibrating cylinder was similar to those previously obtained in experiments, and lock-in (coalescence of cross-flow oscillation and vortex-shedding frequencies at a frequency close to the cylinder natural frequency) was observed. Chaotic cylinder responses were observed over a range of cylinder natural frequencies. Simulations of flows past a cylinder in forced cross-flow oscillation are also discussed, and a result showing an asymmetric P + S vortex shedding mode is presented.