Numerical Simulation of Two-Phase Sloshing Flow in LNG Tank Using Finite-Analytic Level-Set Method

Abstract

Impact pressure due to sloshing is of great concern for the ship owners, designers and builders of the LNG carriers regarding the safety of LNG containment system and hull structure. Sloshing of LNG in a partially filled tank has been an active area of research with numerous experimental and numerical investigations over the past decade. In order to accurately predict the sloshing impact load, it is necessary to develop advanced numerical simulation tools which can provide accurate resolution of local flow phenomena including wave breaking, jet formation, gas entrapping and liquid-gas interactions. In the present study, a new numerical method is developed for the simulation of violent sloshing flow inside a three-dimensional LNG tank considering wave breaking and liquid-gas interaction. The sloshing flow inside a membrane-type LNG tank is simulated numerically using the Finite-Analytic Navier-Stokes (FANS) method. The governing equations for two-phase air and water flows are formulated in curvilinear coordinate system and discretized using the finite-analytic method on a non-staggered grid. Simulations were performed for LNG tank in transverse and longitudinal motions including horizontal, vertical, and rotational motions. The predicted impact pressures were compared with the corresponding experimental data. The validation results clearly illustrate the capability of the present two-phase FANS method for accurate prediction of impact pressure in sloshing LNG tank including violent free surface motion, three-dimensional instability and air trapping effects.

CFD simulations of wave–current-body interactions including greenwater and wet deck slamming

“…The level-set FANS method was employed recently by Chen and Yu [2] and Yu et al [15] for time-domain simulations of greenwater on 2D offshore platforms and 3D sloshing flows in a liquefied natural gas (LNG) tank. In the present study, the method is further extended for the simulation of complex 3D free surface flows including dam-breaking, free jet, greenwater on offshore structures and ship decks, and wet deck slamming.…”

Numerical simulation of 3D sloshing flow in partially filled LNG tank using a coupled level-set and volume-of-fluid method

“…As noted earlier, the level set method is an efficient numerical method to capture sharp and smooth interface, but it is unable to preserve mass conservation. Yu et al (2007) proposed a level set with global mass conservation (LSGMC) method for LNG sloshing flow problem. In the LSGMC method, besides the regular re-distance algorithm, the LS function is also adjusted to compensate for the mass loss.…”

“…The simulations are performed in the grid of dimensions 85 Â 101 Â 85 with a constant time increment of 0.001 T, where T is the motion period. The present grid is identical to that used by Yu et al (2007) and Chen (2011). A systematic grid and time step size refinement study was performed earlier in Yu (2007) using the pure level-set method with satisfactory numerical convergence.…”

“…Wemmenhove et al (2005) extended iVOF method to incorporate two-phase flow and improved the method to simulate the effect of gas bubbles of different sizes. Yu et al (2007) performed the Level-Set Reynolds-Averaged Navier-Stokes (RANS) method for the simulation of liquid sloshing in 2D and 3D LNG tanks.…”

Numerical Investigation of Sloshing in a Tank: Statistical Description of Experiments and CFD Calculations

“…Various methods are in use for computational estimations of fluid pressures due to sloshing [1][2][3][4][5][6], and that list is by no means exhaustive. It can be also mentioned that during the 1 st ISOPE SDD Symposium [7] a number of interesting, currently stateof-art, approaches have been presented, including the approach employing the ComFLOW code used by authors.…”