Study On Pipelay Derrick Vessel Hydrodynamics

To meet the need of exploitation of the South China's sea oil, the CNOOC is building China's first deepwater pipelay derrick vessel,which can pipe to 3000 metres deep. Seakeeping and the design of pipeline are very important for the vessel's safe piping, so time domain numerical simulations and model tests are carried out in order to analyze the hydrodynamic performance of China's first deepwater derrick lay vessel.Model tests had been carried out both with and without pipe and stinger. It is necessary to test the performance of hydrodynamic and pipe in 3000 metres deep, but it's impossible to do this in the current marine engineering basin. In this dissertation, a new project was proposed in 2000 metres deep, which was to use the discreted pipe instead of the consecutive pipe. If the results between the two methods are equal, then we can get the model test results using discreted pipe in 3000 metres deep.At the same time, according to time domain numerical simulations, three results have been calculated, which are the ship's hydrodynamic performance, hydrodynamic performance of ship with discreted pipe and pipe tention, and hydrodynamic performance of ship with consecutive pipe and pipe tention.The researcher then analyzed both the theoretical results and the test results. The main conclusions have been reached as follows:1. The stinger and pipe can play important roles in improving the seakeeping of pipelay vessel.2. The results between ship with discreted pipeline and consecutive pipeline are close, but we can get preciser results using consecutive pipeline in model test.3. The dissertation shows the performances of hydrodynamic and pipe in 3000 and 2000 metres deep.4. The roll can hardly affect the pipe tension, while the heave and pitch are the main factors of affecting the pipe tension.5. In deepwater, the change of sea depth and the weight or motion of pipe have little influence on the motion of ship. The percentage of dynamic stress will change: the percentage of 2000 metres deep is 20%-30%, while 3000 metres deep 10%-20%.