Investigation of planing vessels motion using nonlinear strip theory – an experimental and numerical study

ABSTRACT

This study is aimed to improve Zarnick’s (1978, A nonlinear mathematical model of motions of a planing boat in regular waves. David W. Taylor Naval Ship Research and Development Center, Bethesda, MD, USA) analytical model for motions of planing vessels. A nonlinear time domain mathematical model was developed for dynamic behaviour of longitudinal motion of high-speed planing crafts in regular waves. This model was based on two-dimensional strip theory method using expanding wedge theory and momentum. Due to the nonlinearity and complex dynamic behaviour of these vessels, the time-domain simulation was adopted. Total resistance, heave and pitch motions as well as acceleration were found very sensitive to hydrodynamic coefficients. Furthermore, a set of forced oscillation and seakeeping tests on a vessel were carried out for different conditions at the Marine Engineering Research Centre of Sharif University of Technology (MERC). The effect of velocity, wavelength, and hydrodynamic coefficients were investigated on vessel motions. According to the results, decreasing added mass coefficients, velocity of the model increases. The amplitude of heave and pitch motions declined due to an increase in velocity, within the tested speed range, or by reduction of λ/L ratio. Hydrodynamic coefficients of the mathematical model have been modified accordingly, and the model represented a better agreement with the experimental data obtained by Fridsma (1969. A systematic study of the rough-water performance of planing boats. Tech. Rep. Davidson Laboratory, Stevens Institute of Technology, Hoboken, NJ, USA). This model was applied to identify the nonlinear dynamics of these vessels in both semi-planing and planing phases that can be further expanded to hybrid vessels in the future.

KEYWORDS:

• High-speed planing crafts
• nonlinear strip theory
• forced oscillation and seakeeping tests
• regular wave
• experimental fluid Dynamics (EFD)