FSI기법을 이용한 수중 낙하 구조물의 충격력 추정에 관한 연구

Abstract

There are many methods for crushing seabed rock such as using a free-falling crusher, blasting, and chemical liquid expansion. Blasting and chemical liquid expansion can lead to environmental destruction, noise pollution, and civil complaints. Therefore, a free-falling crusher is recommended for use for seabed breaking. Understanding the characteristics of a crusher in water and the impact force on the ground helps design a crusher and dredge work. In this study, drop tests of 50 and 70-ton crusher models that were scaled down by 15 times were investigated. The tests were conducted in a water basin by the Research Institute of Medium and Small Shipbuilding (RIMS) in Korea. Four water depths were considered with different falling locations: water surface and air. Furthermore, a numerical study on Fluid-Structure Interaction (FSI) analysis for a free-falling crusher was conducted by employing the Arbitrary Lagrangian-Eulerian (ALE) element and the Grüneisen Equation of State (EoS) to fluid models. The crusher and ground were modeled as Lagrangian elements to estimate the impact force on the ground. For FSI approach, ANSYS/LS-DYNA was used to build the model of fluid and structure. A sphere shaped object was dropped in numerical and experimental methods to compare impact force for validation. To enhance numerical efficiency and accuracy, convergence test was carried out to determine appropriate fluid element size and fluid domain dimension. Observed impact force on the ground is similar behavior between numerical and experimental results. It is shown that the angle between the crusher and the ground is a main factor to reduce the impact force during the crusher experiment.