The Study Of The Wave Interaction With Floating Structure

The development of the fish cage has become more and more important for human beings, and a lot of achievements have been obtained in the field of aquacultural engineering. However, moving marine aquaculture from near-shore region into deep-sea has become imperative mainly due to the environmental protection and the coastal utilization problems. Generally speaking, the advantages of developing the deep-sea aquaculture outweigh the disadvantages. However, some troubles have become more serious, such as the heavier waves and/or current forces on the whole system of the fish cage, and the systematic and thorough research into the fish cage system in deep water is a task of top priority. As a result, a national 863 high technology project has been initiated to develop basic research on the hydrodynamics of deep-sea cages. Two kinds of floating structures involved in the project are studied experimentally and numerically. One is the circle float collar of the gravity fish cage, and the other one is the floating breakwater.Having chosen a typical gravity fish cage with the fold-line or the straight-line mooring system, the experiment focuses on the research into movement of the generalized float collar and the tension of the mooring ropes. The numerical simulation is conducted in the time domain. Considering the size of the collar, the wave forces are calculated by the Morison equation, but in the equation the drag coefficient which is affected by many factors is difficult to determine, so in this dissertation the effect of the drag coefficient on the collar displacement is studied. The dynamic response of the mooring rope is considered in the mooring force calculation at every moment. The movement equation of the rigid body is solved to obtain the acceleration, the velocity and the displacement by the fourth order Runge-Kutta method. The comparison of the experimental data and the computational results has testified that the computational method can correctly predict the movement of the float collar and the tension of the mooring ropes.In order to find simple, cheap and effective type of floating breakwaters for open ocean aquaculture engineering, this dissertation introduces three types of structures: the Single-box, the Double-box , the Board and the Board-net. Two-dimensional physical model tests were conducted in a wave-current flume in laboratory to measure the transmission coefficient of these floating breakwaters under regular waves with or without currents. Based on an initial comparison of the wave transmission coefficients, the Board-net floating breakwater was proposed for the project, and detailed experiments were then conducted to examine the effects of several factors on wave transmission coefficient of this type of breakwater including the width of the board, the rows of net, the rigidity of the board, the current velocity, etc. The experimental results show that the Board-net floating breakwater, which is a simple and cheap...