In the present study, the vortex-induced force was investigated for an oscillating rectangular cylinder with the side ratio of 5 (B/D ​= ​5, B: breadth of the cylinder, D: depth of the cylinder) encountering a sinusoidal streamwise gust by wind tunnel tests and computational fluids dynamics (CFD) simulations. For the experiments part, a multiple-fan active-controlled wind tunnel was used to generate the sinusoidal streamwise gust and the vortex-induced force was measured. The results show that the component of total vortex-induced force caused by Karman vortex shedding (denoted as Karman-vortex-induced force) almost disappeared in the sinusoidal streamwise gust, while another component caused by motion-induced vortices (denoted as motion-induced force) remained almost unchanged, regardless of the gust frequency and amplitude. The CFD simulations were performed to shed light on the flow mechanism of vortex-induced force variation. It was found that the flow structure around rectangular cylinder is sensitive to the oncoming flow condition. The alternative vortex shedding in the near wake was suppressed due to the unsteady effects of sinusoidal streamwise gust, which is responsible for the disappearance of Karman-vortex-induced force. However, the vortices induced by the rectangular cylinder motion still exist and lead to the Karman vortex street in the far wake.

在本研究中，研究了边长为5（B / D  = 5，B：圆柱的宽度，D：圆柱体的深度）通过风洞测试和计算流体力学（CFD）模拟遇到正弦流向阵风。对于实验部分，使用多风扇主动控制的风洞产生正弦流向阵风，并测量涡流诱发的力。结果表明，由卡尔曼涡旋脱落引起的总涡旋感分量（称为卡尔曼涡旋诱导力）在正弦流阵风中几乎消失了，而由运动诱发涡旋引起的另一分量（称为运动诱发涡流）则消失了。无论阵风频率和振幅如何，力都几乎保持不变。进行了CFD模拟以阐明涡流引起的力变化的流动机理。发现矩形圆柱体周围的流动结构对即将来临的流动条件敏感。由于正弦流向阵风的不稳定影响，抑制了近尾流中的替代涡流脱落，这是造成Karman涡流感应力消失的原因。但是，由矩形圆柱运动引起的涡流仍然存在，并导致远方的卡尔曼涡街。