Three-dimensional sloshing in a scaled membrane LNG tank under combined roll and pitch excitations

Abstract

This paper experimentally investigates the three-dimensional sloshing in a membrane-type LNG (liquefied natural gas) tank under combined roll and pitch excitations. Seven groups of roll and pitch amplitudes are studied. For each group, the roll and pitch have the same frequency, and around ten frequencies are tested in a frequency band that ranges from 0.5 times of the resonance frequency in the length direction of the tank to 1.4 times of the resonance frequency in the tank breadth. The characteristics of the sloshing waves and impact pressures are analysed in detail. It is found that the steady-state sloshing waves can be classified into four patterns: the length-dominant wave, swirling wave, diagonal wave, and breadth-dominant wave. Highlighted is the swirling wave that is observed in most of the cases where the roll and pitch amplitudes are significant and the excitation frequency locates between the resonant frequencies in the two directions. It is hypothesized that the rotational motion of the tank imposes necessary initial conditions to trigger the swirling wave. The swirling wave is always associated with wave impingements at tank corners and induce violent impact pressures. The practical implementation is that reinforcements of the membrane layer should be added or the sloshing wave should be suppressed near the tank corner to mitigate the damages to the interior layer of the membranetype LNG tank.

Numerical Modeling of Coupled Surge‐Heave Sloshing in a Rectangular Tank with Baffles

“…More complex sloshing excited by two-or three-degree-of-freedom excitations (surge + pitch and surge + pitch + heave) was illustrated by Chen and Nokes [21]. e sloshing waves under other combing forms of external excitations, such as surge + heave + roll and surge + pitch have also been shown by Bai et al [22] and Luo et al [23], respectively. ey concluded that the most violent case could be aroused when the excitation frequencies of all degrees of freedom were close to the system's natural frequencies.…”

Experimental Study on the Sloshing of a Rectangular Tank under Pitch Excitations

“…Understanding the features of sloshing waveforms has been a focal point in sloshing studies [11]. Olsen and Johnsen [12] identified five distinct wave patterns exhibited by free liquid surfaces as excitation frequencies varied, offering comprehensive insights into wave behavior.…”

Research on temperature distribution in container ship with Type-B LNG fuel tank based on CFD and analytical method

“…Over the years, the presence of ultra-large container ships on major liner routes worldwide has been steadily and significant growing. Simultaneously, in the response to the International Maritime Organization's (IMO) stringent regulations regarding nitrogen oxide and sulfur oxides emissions from ships [1], the adoption of liquefied natural gas (LNG) as fuel has emerged as a trend that benefits for emissions reduction and cost-efficiency [2][3]. For the ships which use LNG as fuel, the LNG tank is the main feature which stores the LNG at an ultralow temperature.…”