Research on vortex-induced vibration of elliptic cylinder at different inclination angles

Numerical simulations of vortex-induced vibration (VIV) of an elliptic cylinder with two degrees of freedom were conducted based on the Force Element Analysis, with Reynolds number Re = 200, mass ratio m∗ = 10, damping ratio ξ = 0, and reduced velocity Ur ranges from 1 to 14. The influence of different inclination angle θ and Ur was identified. The force exerted on the elliptic cylinder was decomposed into potential, surface vorticity, and volume vorticity components. The maximum crossflow amplitude shows suppression of 44.6% compared to the circular cylinder only when the θ = 0°, with a noticeably narrower lock-in range of Ur. Within the lock-in range, the volume vorticity lift component Clv contributes negatively to the total lift coefficient Cl, which interpretates that the maximum crosswise amplitude does not match the maximum lift but matches the root mean square (RMS) value of total lift. For other θ (=30°, 45°, 60°, 90°), the maximum crossflow amplitude slightly decreases with increasing θ, with the lock-in range become broader. Changing in θ leads to inconsistencies in the negative contribution of Clv, besides, the phase difference between Clv and Cl slightly increases with decreasing θ, resulting in a greater negative contribution.