Numerical study of U-tube passive anti-rolling tanks

The accurate prediction of the stabilizing effect of U-tube anti-roll tanks has long been of great interest to naval architects. Traditionally, there are two approaches in this area. The majority of the previous work done is limited to model testing only some investigations are performed using approximate mathematical models. In this paper, Computational Fluid Dynamics (CFD) techniques are applied to study U-tube tanks. The Finite Element Method (FEM) is used to formulate the problem and the segregated method is utilized to solve the discretized Navier-Stokes Equations [1] in a local coordinate system. Gauss numerical integration is used to evaluate complicated integrals resulting from the coordinate transformations. Also the moment calculation is based on the finite element concept. The application of the numerical technique herein are restricted to the study of U-tube anti-roll tanks when the ship roll motion is small, slow, and sinusoidal. Moreover, the results correspond to Reynolds numbers corresponding to scale model tests. The goal of this paper is to introduce the Computational Fluid Dynamics technique to the study of stabilizing effect of U-tube anti-roll tanks. It is found that Computational Fluid Dynamics is an effective approach to study the stabilizing effect of U-tube tanks. In order to get more accurate and general results from the CFD study, turbulence models should be used in the case of finite amplitude and finite frequency roll motion [30]. At the same time, numerical techniques to deal with the free surface can also be included in future investigations