Safe Tug Operations during Ship-Assist Manoeuvres

The hydrodynamic interaction effects on a tug operating in close proximity to a larger vessel can result in dangerous situations for the tug. To date most studies have focussed on the interaction effects between the vessels when they are operating in parallel, which represent only one of many practical ship-assist manoeuvres. It is therefore necessary to investigate a wide range of tug-ship combinations to obtain a detailed understanding of these effects. This paper discusses the hydrodynamic interaction effects on a tug operating at various relative positions and drift angles to a larger ship, both moving together at the same forward speed. The hydrodynamic effects were determined using Computational Fluid Dynamics (CFD) simulations that were validated using captive model test data. The range of manoeuvres discussed in this paper provides a comprehensive overview of the hydrodynamic interaction effects on a tug enabling tug operators to identify safe operating envelopes for their vessels.