Research On The Hydrodynamic Interaction Of The Thruster System Of DPS

Propulsion system of DPS is different to the ordinary vessel's, In the DPS, the propulsion system is used to keep vessels in the suitable position, but in the ordinary vessels is to achieve perfect speed. Taken a semisubmersible for example, hydrodynamic performance of DP propulsion system was studied in this thesis.At first, one simple design method of propulsion system is given out in order to carry out farther work, such as DP model test and numerical simulation. And then based on model test and numerical method, it has researched the hydrodynamic characteristics of DP, including thruster-thruster interaction and thruster-hull interaction, aiming for reducing thrust loss and improving efficiency and safety coefficient of the system, providing theory basis for the DP design. In the thruster-thruster interaction study, the hydrodynamic performance of thruster due to the change of distance between thrusters and the azimuth angle of thruster was studied buy CFD method and model test method respectively. The model test of thruster-thruster interaction was carried out in the towing tank,theλof 18 was chose for minimize the scale effect. In the thruster-hull interaction study, a semi deepwater drilling unit which equipped with 8 azimuth thrusters was used to research the thruster-hull interaction during change azimuth angles from 0 to 360 degree. It is proved that thrust loss could reach to 45% due to thrust-hull interaction, and 70% due to thruster-thruster interaction. The main factors causing thruster-hull interaction include Coanda Effect, fiction loss, pontoon effect (semi-platform) and so on. The main methods to reduce thrust loss are to tilt duct of thruster or tilt the whole thruster, and to arrange thrusters with reasonable and effective distance. Besides setting forbidden vector boundary in the optimal thrust allocation logic could greatly improve thruster-thruster interaction characteristics as well.This thesis provides a valuable reference for the practical engineering design of DPS, and an important analytical tool for thruster hydrodynamic interaction study.