On high-speed craft acceleration statistics

Abstract

Design and operation of high-speed planing craft is ruled by the hydrodynamic impact loads and the related craft responses occurring at violent wave encounters. Simulation, measurement and characterization of these loads and responses is however far from trivial. Hereby the general knowledge about these processes is actually rather limited and it is common to rely on simple semi-empirical formulas when designing and analyzing high-speed craft. This paper presents a unique set of impact acceleration data for a high-speed craft in waves, generated based on non-linear strip simulations. Methods and measures for statistical characterization of the acceleration process are established and evaluated, and by application of these methods on the simulation data a number of issues are clarified, for example: slamming time scales and selection of appropriate sampling rates and filtering levels; identification of peak values in acceleration signals; statistical distributions and convergence; and the relation between the statistical peak fraction averages that are commonly used as design parameters and the actual extreme values. The established methods and generated results form a valuable basis for setting up and analyzing high-speed craft experiments and simulations, and for validating and updating the prevailing semi-empirical methods.