Analysis Methods for Evaluating Motions and Accelerations of Planning Boats in Waves

Abstract

For some time, the experimental testing or model planing hulls in rough water has been done by towing tanks throughout the world. The common goal or all these efforts is to provide designers with information that will give them a better understanding or the effects of hull form on the response to waves -in terms of motions, accelerations, added resistance, loads, and operating conditions. It has become increasingly common to analyze the time series data from these experiments using a peak-trough identification. technique (PKT). Once peaks and troughs are identified, they are sorted and averaged over subsets to obtain averages of the 1/m-th highest statistics - which are the statistics currently used by planing boat designers. There are two problems involved with the current approach, one is conceptual and the other is operational: 1) 1 /m-th highest statistics involve the construction of averages based on the number or oscillations observed, however there are no rules for determining the number or small oscillations to be rejected, consequently, 2) the PKT Method requires subjective input from the user that can affect the statistics. This presentation is a joint effort between the Davidson Laboratory and Naval Academy Hydromechanics Laboratory to inform both designers and other experimentalists about the care that must taken in using the average or the 1/m-th highest statistics and to suggest alternative measures or motion and acceleration response that are objective and easy to understand. It is also hoped that this paper will start a discussion with designers about the specific nature of the hydrodynamic data needed to enable more mission and cost effective boat designs to be produced.