Numerical Simulation On The Influence Of Ice Bottom Morphology On Flow Field

In recent years, physical oceanographers and climatologists have paid more attention to sea ice which is an important factor affecting global climate change. Meanwhile, sea ice drift is an important part of the global water circulation, and it produces a major impact on the global climate change and human economic activities in ice-infested seas. Sea ice dynamics mainly focuses on the drift variations, momentum transfer, fracture, overlap and accumulation of sea ice under the actions of oceanic and atmospheric forcing. Wind and flow drag forces play key roles in the dynamic interactions between sea ice and atmosphere, ocean, so they have a direct relationship with the drag coefficient, a parameter that used to describe the sea ice dynamics model. As the wind and flow drag forces will directly affect the sea ice drift velocity, trajectory, even to the dynamic interaction and damage between sea ice, large numbers of researches about the sea ice drag coefficient have been taken since the1950s.According to the observations in-situ, we have got the sea ice drag experience coefficient value of specific sea area using eddy method, profiling method and momentum method, these drag experience coefficients are often taken as constant values and been more concentrated on the air-ice interface, therefore they are usually discrete. For improving the accuracy of the drag coefficient that used in the sea ice dynamics model, parameterization on ice-sea drag coefficient has been a focus of sea ice dynamics model. Numerical simulation about the flow field characteristic under ice have been carried on the basis of physical modeling tests in the thesis, thus some qualitative law of the flow field under ice and the relationship between friction drag and form drag coefficient of the isolated floe and ice geometrical parameters are obtained which will provide the basis support for the drag coefficient parameterization. Meanwhile, using numerical simulation method can further understand the details of ice-hydrodynamic interaction, which can not be directly observed in the physical modeling tests.The thesis has been divided into five chapters. Research background, progress in domestic and overseas and development trend are introduced in the first chapter, where it also points out the theoretical significance and application value of this study. In the second chapter, the main idea and concrete process of the sea ice drag coefficient parameterization method are discussed on the basis of a brief summary on the traditional methods obtaining the drag coefficient. Describe physical modeling tests scheme and process which involves the drag measuring devices and experimental conditions arrangements are explained. The third chapter is forced on the establishment of a two-dimensional mathematical model and the corresponding numerical simulation, such as control equations, turbulence models, mesh and boundary conditions and numerical computation methods, etc. The objective of the fourth chapter is the result verification comparison between numerical simulation and physical modeling tests. Based on the ice model with smooth bottom, Water drag and flow field distribution below ice under different conditions of ice draft and flow velocities were obtained. In addition, flow field dynamics characteristic under and behind the floe model are analyzed following. Comparison shows that the numerical simulation results agreed well with laboratory experimental data from the physical modeling tests, proving the capability of the numerical model as dealing with the dynamic interactions between sea ice and flow field. Numerical simulation about ice model with two different angles of the rough underside is carried in chapter five. Analyze the connection each other of the flow field characteristics under different conditions. Calculate the drag force values that ice suffered and make the comparison with experimental results. The results indicate that range of distortion into the flow field caused by ice became larger as the angles increased under the condition of the same depth into the water. Meanwhile, the vortex range caused in30°angle is larger than that in15°angle. The total drag will change little with the increasing shading angle under the same kind of depth and velocity condition.