Simulation study of approach manoeuvre in lightering and reverse lightering operations

Abstract

Generally, there exists a case wherein a laden service ship approaches a partially loaded very large crude carrier (VLCC) for cargo transfer. This process is called ‘reverse lightering operation’. The manoeuvrability of these nearly fully loaded ships under interaction loads should be understood for the operation safety. In this study, we presented at first a practical method to simulate the approach manoeuvre, taking the interaction loads estimated by a 3D panel method and other hydrodynamic loads based on experiments into consideration. A standard approach manoeuvre of an Aframax tanker to a VLCC was simulated, and the difference in the behaviour of conventional lightering operation and reverse lightering operation was discussed. One result indicated that the service ship might experience difficulty in keeping the heading angle in parallel with the VLCC at the final phase of the approach manoeuvre in the reverse lightering operation. This would be caused by the increase of interaction loads. • A standard approach manoeuvre of an Aframax tanker to a VLCC was studied. • Both lightering and reverse lightering operations were simulated. • Interaction loads between hulls were estimated by a 3D panel method. • The difference in the behaviour between different operations was discussed.