Study Of Characteristic Of Transient Fluid-structure Interaction Of Structures With Airbags Slamming

In recent years, ocean structure water-entry issues have been pay more and more attention.To forecast the structures trajectories and calculate the impact loads has become a key technique. The large impact loads caused by the structures enter into water can damage themselves and change the structures trajectories. This paper uses coupled CEL method to study the above issues. By using numerical simulation method, the paper also presents the changing laws of the impact loads and under water trajectories of cylinders water entry as well as cylinders with air bags. It can be a technical support for the structures design and optimization for ships and ocean structures.Firstly, this paper builds numerical model to simulate the water entry process for cylinders and spheres. Based on coupled CEL method, the paper studies the impact loads and cavitation performance. By comparing the results with experimental data, the accuracy of the model is verified.Secondly, this paper presents how the difference of the speed influences the impact loads in the process of the vertical water entry of cylinders. we also analyzes impact of pitching angles on the water entry loads. A appropriate pitching angle will reduce the impact loads. In the end,the paper studies how the head shapes of the cylinders influence the water entry impact loads by getting different heads shape’s acceleration time history curves. and gives reasonable suggestion for reducing the peak of acceleration.Thirdly, the paper established theoretical calculation model for cylinders with air bags water entry. It analyzes the effects of the volumes and numbers of airbags and the falling speed to the impact loads. This paper also compares the water entry process which the cylinder with or without a air bag, then points out how the air bags influence it. Finally, it analyzes the influences laws of the dropping speed and pitching angle on the impact loads and under water trajectories of cylinders with air bags. It also shows how the impact loads work on the air bags.Finally, by using numerical simulation method, the paper studies the influence laws of shapes, connection locations, internal pressures and material parameters of the air bags on the impact loads as well as underwater trajectories in the process of structure water entry, and finds out the best water entry location and shape of the air bag. The value provides reference for with air bag water entry involves issues.