Model tests of ocean nutrient enhancer "TAKUMI" in deep-sea basin

Abstract

Ocean nutrient enhancer "TAKUMI" is a SPAR type floating structure with a riser pipe with a diameter of 1m, and a length of 175m. By pumping up the deep ocean water containing rich nutrient salt, and sprinkling near the sea surface, plankton is made to increase and it aims at forming a good fishing ground. "TAKUMI" was installed in the Sagami Bay in May 2003 and is also working now. Previous to set up, two kinds of model tests were carried out in the deep-sea basin of National Maritime Research Institute for the performance check. One of the model tests is the enforced oscillation test of a riser model and the other is a test that investigates the response of the whole floating structure in regular waves, irregular waves and current. In this paper, the results of both tests are shown. With the frequency of oscillation, a riser pipe exercises at circular motion or for the form of the figure of 8. Although both results show good coincidence, the position of a node of the enforced oscillation test moves upper a little. About a hull motion and the occurrence frequency of strain, comparison between the result in the actual floating structure and model test was performed.