| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1988: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1987: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
In the fiscal year of 1987, the geology, physical property and developing system of the cobalt-enriched crust deposit were studied by the references which had been already published. Then, the pollowing optimum system for developing the deposit was proposed by pointing many advantages of the hydro-dredge method. This system was composed of a mining ship on the sea surface, a mining robot on the sea bottom and the pipe-string connecting the ship with the robot. In detail, the pipe-string had a pump-module in the middle part and a buffer in the lower end which was connected with the mining robot by a flexible pipe. Furthermore, in order to determine the fluid forces acting on the pump-module and buffer, the drag and added-mass coefficients for various pump-modules and buffers were analysed by the new method developed in this study.
In the fiscal year of 1988, based upon the results obtained in the previous year, the longitudinal vibration of the pipe-string in the above-proposed system was theoretically analysed when the mining ship was forced to vibrate vertically by the external forces due to the sea-state. Then, it was realized that the first resonance could occur and might not be avoided, but that the resonance amplitudes of the pump-module and buffer could be reduced by changing the distribution, mass-ratio and shape of the module and buffer. Furthermore, the maximum axial-stress produced at the top of the pipe-string could be reduced by selecting the proper distribution, mass-ratio and shape of the pump-module and the buffer.
Finally, it was found that the most effective method to reduce the above-mentioned amplitude and stress was to use the pump-module and buffer with larger drag-coefficient.
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