A comparison of experimental measurements of high-speed RIB motions with non-linear strip theory

Abstract

Accurate prediction of the motions of high-speed craft is an essential element in understanding the response of crew to a particular design configuration. The aim of this work is to evaluate the capability of a numerical method for use in the context of a procedure for designing high-speed craft. A numerical model is used to predict the motions of a planing craft in regular waves. The model is based on non-linear strip theory, through calculation of the forces occurring on wedge impact. This numerical model and its limitations are well understood for lower planing speeds (up to a length-based Froude number of around 1.2). This paper describes the limitations and accuracy for higher-speed craft (Froude number around 3). At present there is an inadequate knowledge of the model performance at these speeds. Validation of the model is achieved using experimental data obtained from testing two scale models: A wave piercing rigid inflatable boat (RIB) and an Atlantic 21 RIB. The experiments are conducted in a range of regular wave frequencies for three wave heights. Results are promising, with good correlation between the heave motion of the numerical model and the measured experimental data. Based on these results, a number of potential enhancements to the existing numerical model are discussed.

Keywords:

• High-speed planning craft
• motions prediction
• 2D strip theory

Additional information

Notes on contributors

S G Lewis

Simon Lewis is a research engineer at the University of Southampton, working towards a Doctorate of Engineering. He graduated from Southampton University in 2005 with a Masters in Aerospace Engineering. His research is based on predicting planing craft motions.

D A Hudson

Dr Dominic Hudson is a senior lecturer in the Fluid Structure Interactions Research Group within the School of Engineering Sciences at the University of Southampton. He received his PhD from the University of Southampton in 1999 and then become a research fellow before being appointed to his present position in 2005. He contributes to ship science degree programs and has research interests in hydrodynamics, seakeeping and manoeuvring, especially of high-speed craft.

S R Turnock

Dr Stephen Turnock is a senior lecturer in the Fluid Structure Interactions Research group. He received his PhD from the University of Southampton in 1993, before which he worked as a research assistant at MIT. His current research interests include computational fluid dynamics, marine renewable energy, autonomous underwater vehicles, and ship manoeuvring, propulsion and control systems. He is also secretary of the 25^th ITTC propulsion committee.

J I R Blake

Dr James Blake is a lecturer in the Fluid Structure Interactions (FSI) research group within the School of Engineering Sciences at the University of Southampton. He has a background in the hydrodynamics of highspeed marine vehicles and the use of composite materials in novel marine applications. He has been the leading investigator in the research of hybrid joints for naval applications at Southampton University, a project funded by the UK Ministry of Defence under the Euclid program. His academic duties involve teaching and supervision of Masters level and PhD students. He is the holder of two awards for research at undergraduate and postdoctorate level, and has published widely in refereed journals and international conference proceedings.

R A Shenoi

Professor R Ajit Shenoi is the Lloyd’s Register/Royal Academy of Engineering Research Professor in Lightweight Structures in the School of Engineering Sciences at the University of Southampton. He graduated in 1974 with a degree in naval architecture from the IIT Kharagpur and, after a brief spell in shipbuilding and shipping industries, returned to academe to obtain his doctorate from the University of Strathclyde, Glasgow, in 1981, after which he joined Southampton. His research interests are in the mechanics of lightweight composite structures and design of marine craft.