RIASSUNTO
ABSTRACT:
The RANS computations of a ship with sink and trim motion in head waves are presented. The added resistance, heave and pitch motions are investigated numerically. The computations are based on volume of fluid (VOF) and dynamic deformation mesh methods, discretized by finite volume method (FVM). A six-degrees-of-freedom (6DoF) module is implemented to predict the motions of ship. Four wave conditions with a wide range of wave steepness (0.025 ≤ ak ≤ 0.100) are considered. The wave length of all conditions is one ship length and the results show strong non-linear features, especially for ak = 0.100, where the phenomenon of green water on deck is observed. The comparison of added resistance between the presented computational results and measurements shows good agreements. All computations are performed by our solver naoe-Foam-SJTU developed under the framework of the open source code, OpenFOAM.
INTRODUCTION
The accurate prediction of wave loads, ship motions and added resistance in sea waves is of great importance for ship hydrodynamics. An accurate prediction of added resistance and ship motions can provide valuable information for the design of ship hull to achieve higher safety and better performance in a seaway. Therefore, it's essential to develop an efficient tool to evaluate the added resistance and motions of ship in a seaway. Many previous studies of seakeeping are mainly focused on the potential flow methods. However, the conventional methods still have limitations when handling large-amplitude motions, high-speed vessels and other strong nonlinear problems. With the development of computational techniques and numerical methods, computational fluid dynamics (CFD) has experienced unprecedented developments in the past decades. Since it is based on more realistic model and takes viscous effects into account, CFD can handle more nonlinear problems and obtain more accurate results than conventional methods did.