傾斜した円管に満たされた粘性流体中を降下する鋼球の挙動に関する研究

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It is well known that the falling velocity of a sphere in bounded flow field is much slower than that in open flow field. These studies are of importance as a base for applications, such as falling ball viscosimeter, packed bed, particle fluidization and hindered settling. A series of experiments, where falling velocities and angular velocities of the sphere in a circular tube filled with glycerin were measured, were conducted at various inclination angles in order to investigate their dependence on the inclination angle. When the tube stands vertically, the sphere falls along off-center of the tube axis and rotates in a direction opposite to the direction for contact-type rolling along the side of the cylinder wall to which it was the closest. Present observation is different from the observation by Iwaoka et al. This is because the location of the sphere is hydrodynamically unstable, and the difference between the two observations is thought to be caused by disturbances at initial stage. In inclined tube, the sphere falls along the lowest side of the tube. But a slip was observed between the sphere and the tube wall, and there must be a thin liquid film between the sphere and the tube wall. Even when gravity is modified by cosθ, the falling velocity shows a little dependence on the inclination angle and is well correlated with the following three parameters; the ratio between sphere radius and tube radius, the particle Reynolds number and the ratio between gravity and viscosity. The angular velocity shows general tendency that it decreases with the inclination angle, and the sphere finally rolls down along the tube wall without slip. However, the dependence of the angular velocity on the sphere radius is so complicated that the empirical function can't be derived only by the present data.
独立行政法人海上技術安全研究所の論文
1991-09-30

著者

村田裕幸
原子力技術部

傾斜した円管に満たされた粘性流体中を降下する鋼球の挙動に関する研究

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