Escort tug performance prediction: a CFD method

Date

2012-12-20

Authors

Smoker, Brendan

Journal Title

Journal ISSN

Volume Title

Publisher

Abstract

As the demand for energy continues to increase around the world, more vessels used in the transport of energy, such as Liquid Natural Gas (LNG) and crude oil tankers are being built to transport energy to market overseas. The escort tug has been developed in order to assist in the safe transit of such vessels in confined waterways. Designed to apply emergency braking and steering forces to the stern of a tanker while underway, an escort tug features a hull shape that generates large hydrodynamic lift and drag forces when operating at high angles of attack, this is known as indirect mode. This escorting mode is highly effective at speeds 8 knots and above, often generating towline forces well in excess of bollard pull. Escort performance prediction is a vital aspect of the design of escort tugs. It is important to know a priori if a design will meet the necessary performance criteria. In the past, performance predictions have relied heavily on model testing and empirical methods. With the recent emergence of Computational Fluid Dynamics (CFD) as a commercially viable design tool for naval architects, extensive escort performance predictions can now be carried out more accurately in less time and at less cost than was previously possible. This thesis describes the methodology of a CFD based escort performance prediction method that is accurate and cost effective.

Description

Keywords

marine, scaling effects, turbulence, ITTC, indirect mode, indirect escort, indirect steering, indirect braking, transverse arrest, ASD, tanker, oil safety, staple, skeg, Z-drive, bollard pull, escort butterfly plot, STAR-CCM+, NSERC

Citation