RIASSUNTO
Abstract
The objective of this study is to predict and analyze the viscous flow and the ship-ship interaction between two different tankers KVLCC2 and Aframax advancing in shallow water with same speed and with a fixed separation distance by solving the unsteady RANS equations in combination with the k-ω SST turbulence model. The computational results of the resistance, lateral force, yawing moment, as well as wave height measured by the wave gauge are validated against EFD conducted in Flanders Hydraulics Research (FHR) towing tank. Though the error for case A is not so satisfactory by up to 73%EFD, the tendency is agreed well with EFD data. Moreover, the error case B is much batter by less than 6.25% for both ships. For better understanding of the ship-ship interactions, the wave pattern of the free surface, surface pressure distribution of the ship hull, the asymmetric ship wake and vortex system are also given.
Introduction
With the birth of the very large crude carriers (VLCC) and ultra large crude carriers (ULCC), which have been proven to be one of the best solution to satisfy the demands of oil transportation, a new problem arose. Many ports, which may not be deep enough or have narrow entrances or small births, are not suited to receive ships of such big seizes. On the other hand, a commercial ship which is not under navigating is just a very expensive warehouse. Therefore, the time spent in the harbor, which is mainly determined by the time needed to unload and re-load the oil, must be as short as possible. Both the two problems can be solved by the lightering operation. However, manoeuvring such large vessels without the assistance of tugs at a precision of meters is highly difficult. On top of these difficulties, hydrodynamic interaction forces take place, which influence greatly the relative motion of the vessels. This can result in accidents with important consequences as oil spills or severe damage to the vessels.