ABSTRACT:

The movement of the lifting pipe influences not only its stability but also its flow efficiency. In order to investigate the effects, we developed a finite element model considering liquid and structural transients in a deep ocean mining pipe. Two examples are presented for the validation of the developed model by comparing internal fluid pressure and structural displacement. Dynamic responses of fluid and pipe were almost identical compared to the results of literatures cited. Then the model was also used to perform studies on the vibration of a 5,000 m deep ocean mining pipe and its effects on flow efficiency. The maximum pipe displacement caused by only internal flow in a deep sea lifting pipe was estimated at 0.123 m. Also, the displacement in case of considering internal flow and deep ocean currents showed almost the similar results. Then for the analysis of the effect of pipe behaviors on internal flow, we compared the fluid pressure of the model with that of the case in which pipe was supported rigidly. From the results, the effect of pipe movement on inflow efficiency was found to be negligible. However, we need to analyze the influence caused by additional external forces as the motion of mining ship/buffer in the future work.

INTRODUCTION

For the development of deep-sea manganese nodules, it is essential to acquire the integrated mining technology including collecting and lifting technologies. The lifting system, as the main factor determining the commercial success, consists of pumping (hydraulic and air lifting), buffer and flexible hose systems (Yoon et al., 1998; Yoon et al., 1999). The vertical lifting pipe is the component composing mostly of the mass production line that is connected from the seabed to the surface for the development of deep-sea manganese nodules.

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