Escort Tug Performance Prediction Using Computational Fluid Dynamics

In this paper, we outline and validate a computational fluid dynamics (CFD) method for determining the hydrodynamic forces of an escort tug in indirect towing mode. We consider a range of yaw angles from 0 degrees to 90 degrees and a travel speed of 8 knots. We discuss the effects of scaling on prediction of flow separation and hydrodynamic forces acting on the vessel by carrying out CFD studies on both model and full-scale escort tugs performing indirect escort maneuvers. As the escort performance in terms of maximum steering forces is strongly dependent on the onset of flow separation from the hull and skeg of the tug, the model-scale simulations under-predict the maximum steering force by 12% relative to the full-scale simulations. In addition, we provide a method for converting the hydrodynamic forces of the CFD escort study into towline and thrust forces.