ABSTRACT

Recently, the authors proposed a numerical treatment of impact boundary condition to assure more stable and accurate computation of the sloshing impact loads. This method was incorporated and validated in a 2D sloshing computations. In the present work, this numerical treatment is adopted in the development of a 3D method for simulation of sloshing. The description of the 3D method is given herein with the results of the validation by using four model tanks with both 2D and 3D excitation. The results show the effectiveness of the numerical method for the assessment of sloshing impact pressure in 3D computations.

INTRODUCTION

Assessment of hydrodynamic loads due to sloshing is one of the main concerns in the design of liquid cargo ships such as LNG carriers and VLCC because sloshing loads may cause structural damage.

Since the phenomenon is strongly nonlinear, analytical approaches are difficult to apply and numerical approaches have been widely attempted using FEM, FDM, BEM, etc. Nowadays, both 2D and 3D numerical methods are available for predicting sloshing flows inside a partially filled tank. For the analysis of cases with more complex tank shape or excitation, as in the real ones, 3D methods are required. However, compared to 2D methods, the 3D ones are not so practical for design purpose. One of the main reasons for this is the time consuming computation. On the other hand, while non-impulsive sloshing loads can be correctly predicted by the existing numerical methods, the assessment of the hydrodynamic impact loads is still one of main bottlenecks. According to the reported results (ISSC, 1997), liquid motion and dynamically fluctuating pressure due to a water surface's vertical motion can be calculated with sufficient accuracy by these methods. However, a method for precisely computing impulsive pressure has not yet been established.

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