Extension and Application of ZARNICK: A Nonlinear Simulation Program for High Speed Planing Hulls

Abstract

A nonlinear mathematical model (Zarnick, 1978) has been extended to calculate the motions of a variable deadrise planing boat in waves, using Zamick's low aspect ratio strip theory. It is assumed that the wavelengths are large relative to boat length and that the wave slope is small. The acceleration in the x-direction is assumed small and therefore set to zero enabling the program to solve for the required thrust. A third order polynomial may be used to vary the deadrise of a hull from bow to stern. Several post processors have been written to analyze the motions and accelerations. &&Planing dynamics in a seaway is a complex, nonlinear problem. The Zarnick paper (1978) was the first to formulate the time domain approach for planing hull seakeeping though several authors have duplicated and extended the approach since then (e.g. Payne, 1990 and Keunung, 1992). An extensive bibliography and comparison with experimental data can be found in Payne (1995). &&This report describes the validation of the program and a preliminary variable deadrise study. In the deadrise variation comparison, hull forms are evaluated for reduced drag and operability (i.e. rideability) enhancement.