Investigation of wake-induced vibration interference between two staggered wave-cone cylinders at subcritical Reynolds number

The wake induced vibration (WIV) of a one- and two-degree-of-freedom (1DOF, 2DOF) downstream wave-cone cylinder (WCC) behind a stationary equal-size upstream wave-cone cylinder in the staggered arrangement is numerically investigated at subcritical Reynolds number of 3 900 by using shear stressed transfer (SST) k - ω turbulence model. The streamwise pitch ratios (P / D_m) vary from 4 to 6 with a fixed incident angle α = 8°. Experimental measurements were also performed for the validation of the present numerical models. It is found that the largest vibration amplitude in crossflow direction occurred at P / D_m = 4, U_r =8 with small difference of streamwise vibration at P / D_m = 4, 6. Different from single wavy-cone cylinder (SWCC), the downstream flexible one of a pair staggered WCCs got larger vibration amplitude during phase switching stage instead of in-phase stage. The upstream wake will suppress the triple frequency of main frequency in the power spectra density (PSD) functions of Cl but stimulate the double one of that. An intriguing vibration mechanism happened in all 2DOF cases where the trajectory of downstream WCC is a significant ellipse rather than a figure of 8. The transformation of phase switching and the variation of the main frequency of drag coefficient (Cd) can be explained by the vortex-shedding modes of downstream WCC.