Numerical study on the flow-induced vibrations of two elastically mounted side-by-side cylinders at subcritical Reynolds numbers

Abstract

Two-degree-of-freedom (2DOF) flow-induced vibrations (FIV) of an elastically mounted circular cylinder pair arranged in parallel are numerically investigated in a subcritical Reynolds number range of 1470–10320. The two cylinders are identical with mass ratios of m⁎ = 2.6 and mass-damping parameters of (m⁎ + Ca)ζ = 0.013. The transverse centre-to-centre spacing ratio (Sy/D) between them is varied from 4.0 to 10.0 with an increment of 2.0. The effect of Sy/D on the FIV responses, hydrodynamic features and wake patterns is evaluated. It is found that the response amplitudes of the two cylinders show similar variation trends and both drop to smaller values earlier than an isolated cylinder when Sy/D = 4.0, 6.0 and 10.0. Whereas, their response characteristics are different at Sy/D = 8.0. Cylinder #1 reaches its peak in-line (IL) and cross-flow (CF) amplitudes equivalent to those of the single cylinder, while the vibration amplitudes of Cylinder #2 experience decreases at Vr = 8.0. Moreover, the results suggest that the interference between the two cylinders is nonnegligible for all the Sy/D values considered in the present study. Six wake patterns are identified including the asymmetric long period flip-flopping (ALFF), asymmetric shear layer (ASL), biased in-phase synchronised (BIS), asymmetric shedding (A-Shed), in-phase synchronised (IS) and anti-phase synchronised (AS) patterns. The asymmetric wake patterns give rise to the distinct vibration modes of the two cylinders.