Study on the Effect of Density Ratio of Gas and Liquid in Sloshing Experiment

Abstract

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper presents the results of sloshing experiments having different fluids in model tanks with various density ratios. The experimental model consisting water and air at ambient, which has been commonly used, is not consistent in density ratio with that of an actual LNG cargo tank. Therefore, an advanced experimental scheme is developed to consider the same density ratio of LNG and NG by using a mixed gas of sulfur hexafluoride (SF 6 ) and nitrogen (N 2 ). For experimental observation, a two-dimensional model tank of 1/40 scale and a three-dimensional model tank of 1/50 scale have been manufactured and tested at various conditions. Two different fillings with various excitation frequencies under regular motions have been considered for the two-dimensional model tank, and three different filling levels under irregular motions have been imposed for the three-dimensional model tank. The density ratio between gas and liquid varies from the ratio of the ambient air and water to that of the actual LNG cargo container, and the different composition of gas is used for this variation. Based on the present experimental results, it is found that the decrease of sloshing pressure is predicted when the density ratio increases.

Numerical Study of Density Ratio Influence on Global Wave Shapes Before Impact

“…From sloshing model tests performed with water and different ullage gases or vapor (Maillard and Brosset (2009), Ahn et al (2012)), it has been shown that, statistically and for all level of probability to be considered, the heavier the ullage gas, the smaller the pressures. Based on this result, sloshing model tests for any project of LNG floating tank are now performed with a heavy gas made of a mixture of SF 6 and N 2 tuned in order to match the DR in real LNG tanks (close to 0.004).…”

Study on tank shape for sloshing assessment of LNG vessels under unrestricted filling operation

“…Because the same liquid and gas were used for both the conventional and the modified tank, the influence of the density ratio was not relevant. There are several studies on the influence of liquid-gas density ratio in sloshing [14,15].…”

Outlier analysis of sloshing impact loads on liquid ship cargo

“…12 Furthermore, either short-term or long-term model test is suggested, according to our experiment, the recommended minimum time for model test seems significantly lower than the time for convergent pressure prediction. [13][14][15][16] This paper introduces an outlier analysis method, which can improve the convergence through the statistical analysis of experimental values lacking convergence, and is based on the doctoral thesis of Kim 17 and also extending the study of Kim and Kim. 18 In this study, a new method is proposed to detect and treat anomalies in the sloshing model experiment data.…”