In order to investigate the effect of the entrapped air on liquid impact, a series of experiments are designed and performed in an elastic rectangular tank under nearly 2D shallow-water condition. The evolution of free surface and the development of entrapped air near the vertical wall are recorded by the high-speed camera. Furthermore, the impact pressure and the wall deformation during slamming are measured. The results show that the presence of entrapped air can change the impact mode. Furthermore, the impact pressure and wall deformation induced by liquid slamming decreases due to the entrapped air, which shows the air cavity plays a cushion effect during liquid slamming. It is suggested to consider air compressibility during liquid slamming with entrapped air.
The challenges to design Floating Liquefied Natural Gas facilities have attracted enough attention from industry and academia. The FLNG is used for production, liquidation, storage and unloading offshore gas. Therefore, the FLNG system needs lager volume tanks and has no restrictions of filling condition. Liquid tends to slosh in a partially tank during shipping. Sloshing-induced slamming in a tank at low filling depth resulting in the structural local damage during FLNG shipping is one of the main loads in the design of super-large storage tanks (Gavory and De Seze, 2009). Thus, it is important to determine the slamming load and investigate the physical evolution of a wave impact during the sloshing process in a partially field tank. But during liquid impact, the physical phenomena with gas-liquid, gas-solid and gas-liquid-solid are complicated for researchers to predict the evolution of free surface and slamming load with theoretical and numerical methods (Abramson et al., 1974; Lee and Choi, 1999; Faltinsen and Timokha, 2009). For example, Delorme et al. (2008) numerically found that the maximum pressure calculated by their numerical method is greater than the experimentally measured values due to the presence of air. Therefore, from physical mechanics point of view, it is necessary to use experimental methods to study the liquid impact with entrapped air in the tank.