下端にバッファをもつ揚鉱管の動力学的挙動

マンガン団塊の採鉱に伴う揚鉱管の挙動 (第2報)

抄録

In this paper, the dynamic behavior of a submerged pipe string, which was hanging from a ship and equipped with a buffer at its lower end, was theoretically analysed for the design of a mining system in the deep ocean.
The main results obtained are as follows:
(1) The relative displacement of the pipe string to the ship continues to increase just as a pendulum even in the towing period of a constant velocity, which follows the period of acceleration, and then it approaches to the steady-state value after a considerably long time.
(2) The bending stress induced in the pipe string is much smaller than the tensile stress at the top of the string. Hence, the bending stress does not play an important role in designing the above-mentioned mining system.
(3) When the maximum towing velocity is constant, the variations of acceleration and deceleration times in towing have a little effect on the relative displacement of the pipe string. However, both the relative displacement and the time required for it to reach the steady-state value increase remarkably as the maximum towing velocity increases.
(4) From the practical sense, it can be said that the flow velocity of fluid in the string does not affect the displacement of the string for the mining system considered here.
(5) When the other quantities are constant, both the relative displacement of the string and the time required for it to reach the steady-state value increase remarkably as the mass of the buffer decreases or as its projected area to the vertical plane increases. Furthermore, a larger ratio of height to diameter of the cylindrical buffer leads to a smaller displacement of the string.