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.