Flow-structure interaction of the parachute in inflation process

降落伞有很强的灵活性，因为它是由织物制成的。由于降落伞的柔性，使得降落伞的流固耦合分析变得非常困难。即使我们将刚性降落伞作为一阶近似，我们碰巧遇到身体和尾流之间的强非线性。本文采用数值模拟和水洞实验相结合的方法，研究了降落伞的动态运动，着重研究了降落伞周围的流场波动。降落伞的运动表现为钟摆运动，其中由于加速运动，虚质量（附加质量）效应起着重要的作用。为了得到精确的数据，提出了高精度的简单近似方法，并进行了二维数值模拟，以捕捉其膨胀过程。其次，在讨论了虚拟质量和柔性壁模型的影响后，进行了三维仿真。数值计算结果与实验结果（流动显示）相结合，澄清了流动结构。它的振荡模式分为三类（直线，圆弧，圆周运动）。最后指出了降落伞研究的方向。

The parachute has a strong flexibility because it is made of a fabric. Therefore, the instantaneous shape is formed by the difference between within and outside it. It is so hard to analyze the fluid-structure interaction for the parachute because of the flexibility. Even if we would apply for the rigid parachute as a first order approximation, we happen to meet the strong non-linearity between the body and the wake. In this investigation, the dynamic motion of it is focused by using the numerical simulation and the water tunnel experiment, in which the flow fluctuations around the parachute are focused.First, the parachute is assumed as a rigid rounded hemisphere body, in which it is not deformed. The motion of the parachute shows the pendulum motion, in which the virtual mass (added mass) effect plays an important key because of the accelerating motion. In order to get data precisely, the high accuracy simple approximation method is proposed to apply for it.In order to catch the inflation process of it, the 2 dimensional numerical simulation has been carried out. When the folded parachute is inflated, the snatched force is caught in detail in our simulation.Second, after the effect of the virtual mass and the flexible wall model are discussed, the 3 dimensional simulation has been carried out. The flow structure is clarified by he numerical results together with the experimental results (flow visualization). The oscillation patterns of it are classified into three categories (lineal ; arc, circular motions). Furthermore, the guide of the parachute study into future is shown.