The purpose of this study is to observe effects of the gas-liquid density ratio on the sloshing experiment. Due to the recent significant demands of LNG fuel, a size of LNG container vessel has been increased, and the volume of its cargo containers has been also increased. This increase leads the natural frequency of sloshing inside of the cargo to that of the vessel; problems caused by sloshing needs to be considered, and classification societies recommend experimental approach by using a model tank rather than computational approach or analytical approach.
Being carried out, sloshing experiments produce their results which need appropriate scaling for considering parent ship design. Identifying the nondimensional parameters has been generally conducted, and a few researches have concluded that Froude number may represent sloshing pressure. However, Froude number has many limitations such as ignoring the local phenomena or chances of thermodynamic effects. Therefore, several nondimensional parameters have been suggested, and one of the numbers is the gas-liquid density ratio.
The presents study focuses on this density ratio, and observe its influence on the sloshing phenomena. Three tests have been set up. Conditions of the first test are harmonic and regular. Two-dimensional model tank has been mounted, and the density ratio varies for each condition. Its influence on the sloshing impact peak pressure is measured and compared. Next, the purpose of the second test is similar with the first one, but conditions are irregular, and 160K LNG cargo container has been selected as a model tank. For the last test, Particle Image Velocimetry (PIV) experiment has been applied for the sloshing experiment under the regular conditions. Several technical problems exist for this application, and solved in the present study. PIV experiments give the kinematic and dynamic results of flow, and they are compared with the experiments which have the different density ratio.
The first and the second test insist that the increase of the density ratio generally lead decrease of the sloshing peak pressure, and the third test, variation of the density ratio changes the kinematics and dynamics of flow.