Research On Heaving Damping Characteristics Of Deepwater Spar Platform With Moon Pool

The centerwell of Spar throughout the entire body from bottom to top, and there are riser and important drilling facilities to be lay out. They are make up the moon pool of Spar. The moon pool of the spar platform is semi-closed sometimes according to the design requirements, which allows water to flow freely in and out of the moon pool through the guide plate. The mass of water inside the moon pool is comparable to the platform mass itself if the top tension riser system is used. Then the effect of the moon pool water on the hydrodynamics of the platform should not be ignored. Based on CFD method, the added mass and viscous damping of Spar platform have been studied in this paper, we also compare and analyze the influence of the opening area of the pool on the platform hydrodynamic parameters, calculate the platform’s attenuation movement in static water, and obtain viscous damping of the Spar platform heaving motion considering fluid in the moon pool.This paper establish a platform which is a cylinder structure model, and analyze the effects of mesh quantity and time step, therefore get the options which meet the requirements of precision. It calculated added mass coefficient, viscous damping coefficient and dynamic pressure of the platform with different openings, flow velocity and KC number. It established structure with platform main body-the moon pool fluidheaving plate-soft tank, and calculated dynamic pressure, mass flow rate, viscous damping force of guide plate, viscous damping force of heaving plate, and viscous damping force of the whole Spar. It studied the viscous damping coefficient in static water with considering fluid-structure interaction. Step by step, get the damping force from Fluent, and import it to heaving motion dynamic equations, and then calculate. By analyzing the heave curve histories, get viscous damping coefficient which compare to experimental results.Results show that natural period and added mass increase with opening. This makes heaving modal frequency away from the frequency of wave energy concentration, and reduce heaving motion. There are different heaving damping with different opening. In practice, we can design the opening of guide plate to maximize reduce the heaving motion of the whole Spar. In this paper, guide plate with 30% opening have the minimum dynamic and the maximum heaving damping. Comparing with model experimental results, this paper verified the correctness and rationality of numerical method.