Free surface anti-roll tank simulations with a VOF based Navier Stokes solver

Ship roll stabilization has received attention for more than a century. From a wide variety of anti-roll devices, the anti-roll tank (ART) is considered for its simplicity, low cost and action at low or even zero speed. In the past several types of ARTs have been proposed and tried in practice. The simplest type of ART is the free surface ART (FSART).
The physical phenomenon in a FS-ART must be classed in the group of wave problems in shallow water. The main stabilizing action is created by a bore travelling up and down the tank, which is a strongly non-linear phenomenon. Therefore it is unlikely that any linear or weakly non-linear theory will produce reliable approximations for the FS-ART action. For this reason an experimental procedure was foUowed by Van den Bosch and Vugts (1966) to collect information about the performance of the FS-ART. It was forced to execute sinusoidal oscillations about a fixed axis while amplitude and phase of the moment about this axis were measured. Systematic measurements were done for a wide range of tank and motion parameters. This experimental data set is used at MARIN to account for the effect of a FS-ART on the rolling motion of a ship. Since these frequency domain results are useful in regular wave conditions only, there is a need for a numerical time domain method to predict the tank forces and moments for a ship sailing in irregular waves. The computer program ComFlo solves the Navier-Stokes equations for unsteady incompressible fluid flow in complex geometries. The method is based on the Volume Of Fluid (VOF) method - see Hirt and Nichols (1981). ComFlo has found many applications in a variety of flow problems, ranging from sloshing in fuel containers onboard satellites to green water loading on the fore deck of a ship. The program has proven to be robust and accurate. All experiments of Van den Bosch and Vugts were simulated with ComFlo as a first step in an extensive validation program. The results are presented in this abstract. For a description of the mathematical model and the numerical implementation in ComFlo we refer to Gerrits (1996) or Loots (1997).