Abstract This paper reports on an extensive numerical investigation of the effects of pivot location and mass ratio ( m ∗ = solid/fluid mass) on flow-induced vibration (FIV) of a foil undergoing fully passive two-degree-of-freedom (2-DOF) plunging and pitching motion in a two-dimensional free-stream flow. Here, the normalised pivot location is defined by x = x p ∕ c , with c the foil length and x p the distance to the foil leading edge. A comprehensive set of numerical simulations were conducted employing an Immersed Boundary Method at a Reynolds number of 400. By analysing the FIV dynamics for three selected mass ratios, m ∗ = 5 , 20 and 200, at two pivot locations, x = 0 . 35 and 0.50, it is found that there are two types (type-I and type-II) of FIV responses, one is primarily a driven static instability while the other is strongly associated with vortex shedding. Interestingly, for x = 0 . 50 , which is close to the mass centre, increasing the mass ratio can favour suppression of the chaotic response. Importantly, it is shown that there exists a critical mass ratio, above which the foil oscillations are suddenly suppressed. The findings indicate that the combined effects of eccentricity and mass ratio on the foil dynamics can be profound.

中文翻译：

---

枢轴位置和质量比对完全被动扑翼的流动诱导振动的影响

摘要 本文报告了枢轴位置和质量比（ m * = 固体/流体质量）对经历完全被动二自由度的箔的流动诱导振动（FIV）影响的广泛数值研究（2 -DOF) 二维自由流中的俯冲和俯仰运动。在这里，归一化的枢轴位置由 x = xp ∕ c 定义，其中 c 是箔片长度，xp 是到箔片前缘的距离。在雷诺数为 400 时，采用浸入边界法进行了一组全面的数值模拟。通过分析三个选定质量比的 FIV 动力学，m * = 5、20 和 200，在两个枢轴位置，x = 0。35 和 0.50，发现 FIV 反应有两种类型（I 型和 II 型），一个主要是驱动的静态不稳定性，而另一个与涡旋脱落密切相关。有趣的是，对于 x = 0 。50 靠近质心，增加质量比有利于抑制混沌响应。重要的是，它表明存在一个临界质量比，高于该临界质量比时，箔片振荡会突然被抑制。研究结果表明，偏心率和质量比对箔动力学的综合影响可能是深远的。