Abstract In this paper, the drag forces on a rigid segment of a twin-tube submerged floating tunnel (SFT) under various Re number and submergence are experimentally investigated with a simplified rigidly connected tandem twin-cylinder model towed in a tank. The effects of the spacing distance between two cylinders and vortex-induced vibration (VIV) on the drag forces are investigated through stationary and self-oscillation towing tests. It is found that, in the stationary cases, the drag forces on the cylinders act in opposing directions when the spacing ratio is 2 and 3, which leads them attracting each other. Under VIV conditions, the drag forces are significantly amplified. The maximum mean drag coefficients of the up- and downstream cylinders increase from 1.27 to 4.1 and 0.43 to 1.7, respectively. As for the submergence effect, it is found that both the VIV response amplitude and mean drag coefficient decrease with the decreasing of the submerged depth, especially when the depth ratio is below 3.7.

中文翻译：

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双管水下浮式隧道管片模型拖曳力试验研究

摘要 在本文中，用一个简单的刚性连接串联双缸拖入坦克模型，实验研究了在不同Re数和淹没度下双管沉没浮式隧道（SFT）刚性段的阻力。通过静止和自振荡牵引试验研究了两个圆柱体之间的间距和涡激振动 (VIV) 对阻力的影响。发现在静止情况下，当间距比为2和3时，作用在圆柱体上的阻力作用在相反的方向，导致它们相互吸引。在 VIV 条件下，阻力显着放大。上游和下游气缸的最大平均阻力系数分别从 1.27 增加到 4.1 和 0.43 到 1.7。至于淹没效果，