We investigate bag and floater motions of a scaled fabric membrane cage model. Model tests with an assumed model scale of 1:27 were performed at SINTEF Ocean’s towing tank, where the cage model consisted of an enclosing fabric (or a bag), an elastic floater, a mooring system, and an internal water mass. The model was moored in a towing tank and subjected to regular waves with different periods and steepnesses. The first harmonic component of the floater and bag motions time series were analyzed, and image analysis was performed for the latter. Several interesting responses of the fabric membrane cage are discussed: cage set-down, wavelike bag motion, and floater motions. The magnitude of the cage set-down is dependent on the incident wave period and steepness; the magnitude increases in response to a longer and steeper wave. The bag also exhibits a wavelike motion that propagates from the floater to the bottom part of the cage and has apparent implications for the dynamics of the bag bottom and the snap loads on the fabric material. Simplified numerical simulations were performed using WAMIT, which assumed a rigid cage model. A floater motions comparison between model tests and WAMIT results shows the importance of taking the bag and floater flexible modes into account when performing hydrodynamic analysis of a fabric membrane cage.

我们研究了缩放织物膜笼模型的袋子和漂浮物运动。在 SINTEF Ocean 的拖船舱中进行了假设模型比例为 1:27 的模型测试，其中笼子模型由封闭织物（或袋子）、弹性浮子、系泊系统和内部水团组成。该模型系泊在拖曳水箱中，并受到不同周期和陡度的规则波浪的影响。分析了漂浮物和袋子运动时间序列的一次谐波分量，并对后者进行了图像分析。讨论了织物膜笼的几个有趣的反应：笼子放下、波浪状袋子运动和漂浮物运动。笼子下沉的幅度取决于入射波周期和陡度；幅度随着更长更陡峭的波而增加。袋子还表现出从漂浮物传播到笼子底部的波浪状运动，并且对袋子底部的动力学和织物材料上的卡扣载荷具有明显的影响。使用 WAMIT 进行了简化的数值模拟，它假设了一个刚性笼模型。模型测试和 WAMIT 结果之间的浮子运动比较表明，在对织物膜笼进行流体动力学分析时，考虑袋子和浮子柔性模式的重要性。