This paper reports the numerical results of the flow-induced vibration (FIV) of a trapezoidal cylinder with base length ratio of 0.3 placed at various flow orientations. Three typical attack angles ($\theta$) of 0° (shorter base facing flow), 90° and 180° are examined in the computations that carried out for a reduced velocity range of ${\mathit{U}}_{\mathrm{r}}=2\text{–}20$ at a low Reynolds number of 150. The vortex-induced vibration (VIV)-desynchronization regime is observed in the trapezoidal cylinders with $\theta =0°$ and $\theta =90°$. In contrast, instead of the VIV lower and desynchronization branches, galloping emerges at ${\mathit{U}}_{\mathrm{r}}$ > 4 for the trapezoidal cylinder at $\theta =180°$ with a continuous growth of response amplitude, presenting the full interaction between VIV and galloping. The response regime is associated with the energy transferred and the vortex shedding mode as well as the added mass coefficient and the phase lag between the cross-flow displacement and the lift coefficient. In the VIV branch, more energy is extracted from the ambient flow by the trapezoidal cylinder in comparison with the square cylinder, and it grows with the attack angle. The transferred energy is further increased when the cylinder undergoes galloping response, while it is significantly reduced when the response enters into the desynchronization branch. Although the typical 2S vortex shedding mode is observed at $\theta =0°$, the transition from the primary vortex street to the secondary vortex street emerges in the wake. The P* and P*+S modes occur in the VIV branch of 90°-and 180°-oriented trapezoidal cylinders, respectively, where P* denotes the reborn pair of vortices that is merged from a single vortex and a pair of ones. In the galloping branch, P*+S, 2P+2S, 4P+2S and 6P+2S modes successively occur with increasing ${\mathit{U}}_{\mathrm{r}}$, due mainly to the elongation of oscillation journey.

本文报道了基长比为0.3的梯形圆柱体在各种流动方向上的流动引起的振动（FIV）的数值结果。三种典型的迎角（$\theta$）的0°（较短的基本面流量），90°和180°的计算在减小的速度范围为 ${\mathit{ü}}_{\mathrm{[R}}=\mathrm{2个}\text{–}20$ 在150的低雷诺数下。在具有以下特征的梯形圆柱体中观察到了涡激振动（VIV）失步状态 $\theta =0°$ 和 $\theta =90°$。相比之下，代替VIV较低和取消同步分支，则在${\mathit{ü}}_{\mathrm{[R}}$ > 4的梯形圆柱 $\theta =180°$响应幅度的连续增长，呈现了VIV和舞动之间的完全相互作用。响应方式与传递的能量和涡旋脱落模式，附加的质量系数以及错流位移和升力系数之间的相位滞后有关。在VIV分支中，与方形圆柱体相比，梯形圆柱体从环境流中提取了更多的能量，并且能量随迎角而增长。当气缸经历驰豫响应时，传递的能量会进一步增加，而当响应进入去同步分支时，传递的能量将显着降低。尽管观察到典型的2S涡流脱落模式$\theta =0°$随之而来的是从主要涡街到次要涡街的过渡。P *和P * + S模式分别出现在90°和180°梯形圆柱体的VIV分支中，其中P *表示从单个涡旋和一对涡旋合并而来的复生涡旋对。在奔腾的分支中，P * + S，2P + 2S，4P + 2S和6P + 2S模式随着增加而连续发生。${\mathit{ü}}_{\mathrm{[R}}$，主要是由于振荡行程的延长。