Numerical Simulation Of Ship Roll Motion In Viscous Flow

It is well known that, as ship roll motion is the most important reason which leads to ship capsizes, it is the most dangerous threat to the safety of ship. As there are some viscous phenomenon in the ship roll motion, such as flow separation and vortex escape from ship's bilge, and there are also some nonlinear nature in the roll motion, such as jump and bifurcation, so in order to accurately predict the roll characteristics in waves, the most critical problem is to accurately determine the roll damping. But so far, the theoretical calculation for roll damping can't be used in engineering. In this paper, numerical simulation study on the ship roll motion is carried out through the CFD software FLUENT.(1) Base on the numerical simulation theories, two-dimensional finite volume models of ship roll motions are established by using the volume of fluid (VOF) and unstructured dynamic mesh technique in FLUENT.(2) Base on the models, a numerical simulation of free roll decay motion for a barge section (blunt ship) without forward speed in still water is carried out. The obtained numerical results are agreed well with the corresponding experimental ones. At the same time, the effect of viscosity is analyzed, and the cause of eddy damping is discussed.(3) A numerical simulation of free roll decay motion for a ship with rounded-corner bilge in still water is carried out. In comparison with blunt ship, the effects of eddy damping on the roll hydrodynamic coefficients are analyzed.(4) A series of numerical simulations of large roll decay motion for a blunt ship in still water are carried out, and the nonlinear characteristics of roll motion are investigated. The initial roll angles areΦo=10o,15o,20o,25o,30o respectively.(5) A series of numerical simulations of large roll decay motion for ships with different rounded-corner bilge in still water are carried out, and the statistical characteristics of nonlinear roll motion are investigated.(6) A series of numerical simulations of prescribed roll motion for a blunt ship in still water are carried out. Series variations are presented to study the effects of frequency, amplitude, and the presence of viscosity.