Underwater structure is a special kind of marine equipment, which mainly works underwater, and sometimes it needs to rise freely. So making research on its rising motion and assessing its safety are an important part in the development and design of underwater structure. In the research, development and design of underwater structure, model experiment is often used to study its rising motion. However, whether the model experiment result can fully reflect the free rising motion of prototype is still inconclusive. In this paper, spheres are chosen as research objects to study the influence of scale on their rising motions by means of CFD method, and explore the relationship between the rising motions of model and prototype. Finally, a prediction method is proposed, which can be used to predict the stable rising velocity of prototype through model experiment result.

For a ship sailed in seawater, it is only a matter of time before its immersed surface is covered by marine fouling. Fouling expands the outer dimensions of the ship, alters the flow regime around the ship and changes the hydrodynamic forces acting on it. The aim of this study is to investigate the effect of biofouling on a oceangoing ship by taking into consideration the resistance components using a Computational Fluid Dynamics (CFD) solver. The geometric model of the ship and fouling organisms around the hull are first established. Following that, the validation study is performed for the numerical simulation method in smooth condition with the available experimental data. Finally, the effects of biofouling on the individual ship resistance components are investigated.

In the design of the offshore nuclear power platform, the main engine compartment discharges warm drainage. It will make the seawater at the water inlet of the cooling water system have a certain degree of temperature rise, thus affecting the cooling effect. In this study, the CFD method is used to simulate the diffusion of warm drainage under a typical working condition firstly. After obtaining good consistency with the experimental results, the diffusion law of the warm drainage with the change of the environmental flow velocity was obtained by changing the ocean current velocity. Finally, a partial design was carried out at the bottom of the ship: a baffle was added between the water outlet and the water inlet. Two parameters of the baffle are determined: position and height. The result shows that reasonable addition of baffles can effectively reduce the temperature rise at the water inlets, and will not cause too much effect on the ship resistance.