Abstract
One-degree-of-freedom (1-dof) and two-degrees-of-freedom (2-dof) flow-induced vibrations (FIVs) of square and rectangular cylinders at a mass ratio of 10 and a low Reynolds number of 200 are studied numerically by solving the two-dimensional incompressible Navier-Stokes equations. The aim of the study is to identify the effects of the aspect ratio α, defined to be the ratio of the cylinder dimension in the cross-flow direction to that in the inline direction, on the vortex-induced vibration (VIV) and galloping responses. Simulations are conducted for aspect ratios of 0.3, 0.5, 0.7, 1 and 1.25 and reduced velocities ranging from 1 to 30. Distinct VIV lock-in and galloping regimes are found for all the aspect ratios except α = 0.3, for which only VIV lock-in is found. The VIV lock-in regime and the galloping regime are separated by a reduced velocity range, where the response amplitude is very small and the response frequency is a linear function of the reduced velocity. It is found that the maximum amplitude in the VIV lock-in regime decreases with increasing aspect ratio. Galloping does not start until the reduced velocity exceeds a critical value. The critical reduced velocity for galloping increases with increasing aspect ratio. For α = 0.5, galloping starts at Vr = 7 and 6 for 1-dof and 2-dof vibrations, respectively. The critical reduced velocity for galloping is increased to 17 at α = 1.25 for both 1-dof and 2-dof vibrations. Because the response amplitude in the inline direction is much smaller than that in the cross-flow direction, the response amplitude and frequency in 2-dof vibration are very similar to their counterparts in 1-dof vibration. However, the response amplitude in 2-dof galloping is greater than that in 1-dof galloping. A 2T vortex shedding mode is observed in the VIV lock-in regime for α = 0.3 and 0.5.
Original language | English |
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Article number | 25502 |
Number of pages | 24 |
Journal | Fluid Dynamics Research |
Volume | 47 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2015 |
Keywords
- Reynolds number
- circular cylinders
- vibration