Smoker B.,Robert Allan Ltd. |
Stockdill B.,Robert Allan Ltd. |
Oshkai P.,University of Victoria
Journal of Ship Research | Year: 2016
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° to 90° 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. © 2016, Society of Naval Architects and Marine Engineers. All rights reserved.
Allan R.G.,Robert Allan Ltd. |
Harford K.D.,Robert Allan Ltd. |
Noon D.,Robert Allan Ltd. |
Bjerkeset J.,Robert Allan Ltd. |
And 2 more authors.
Transactions - Society of Naval Architects and Marine Engineers | Year: 2010
The Three Forty-Three is the first of two new fireboats to this design built at Eastern Shipbuilding Inc. of Panama City, Florida and delivered in May 2010. The second vessel is due for completion later in the year. As the result of an international design competition, Robert Allan Ltd. was selected to provide complete engineering and design services for the new boats, from initial concept through detailed engineering design and a comprehensive value engineering process. The scope of services also included the support of FDNY through every stage of major component procurement and the shipbuilding contract award. Robert Allan Ltd. 's shipyard supervisory staff also acted in the capacity of Owner's Representatives on-site in the shipyard throughout the entire construction process. These major, fast response fireboats were designed to specifically address the fire-fighting and rescue needs of the greater New York harbour, including the New Jersey shore. This includes the capability within the vessel to respond to any Chemical, Biological, Radiological, and Nuclear (CBRN) incident. Thefireboats are designed for a response speed of 17.4 knots, with a low-wake, 12-knot cruising/patrol speed. The powering seakeeping and wake-generation characteristics of the semi-displacement hull form were all verified in an extensive model-testing program. The resulting propulsion system is a unique quadruple screw, CPP configuration. This paper focuses on the various initial studies performed to establish the basic design configuration, the model testing and performance verification process, the value engineering studies performed, the many unique design features of the fire-fighting and emergency response capability of these vessels, and the performance trials results. Finally, the challenges of managing a major shipbuilding project for a major civic government client, such as the FDNY, concludes the paper.