Abstract
In this paper, the validation of the hybrid frequency–time domain method for the assessment of hard chine displacement hull from vertical motions is presented. Excitation and hydrodynamic coefficients in regular waves are obtained from the 3D panel method by Hydrostar® software, while coupled heave and pitch motions are calculated in the time domain by applying the Cummins equations. Experiments using a 1:15 scale model of a “low-drag” small craft are performed in irregular head and following waves at Froude numbers Fr: 0.2, 0.4, and 0.6 at University of Naples Federico II, Italy. Results obtained by hybrid frequency–time domain simulations for heave, pitch, and vertical accelerations at center of gravity and bow are compared with experimental data and showed high accuracy.
Highlights
The assessment of ship behavior in an irregular seaway is one of the most difficult hydrodynamic problems
A large variety of different computational methods have been presented in the past three decades and are discussed in Hirdais et al [1]. They proposed the subdivision into six levels, where each “level” introduces mathematical models closer to the physical models, generally moving from frequency domain calculations to time domain simulations, from linearized to nonlinear boundary conditions, and from small wave amplitudes to breaking waves, spray, and water flowing onto and off the ship’s deck
Frequency domain methods have been widely used as strip theories (2D) or as panel methods (3D) with different levels of nonlinearities considered in the mathematical model
Summary
The assessment of ship behavior in an irregular seaway is one of the most difficult hydrodynamic problems. A large variety of different computational methods have been presented in the past three decades and are discussed in Hirdais et al [1] They proposed the subdivision into six levels, where each “level” introduces mathematical models closer to the physical models, generally moving from frequency domain calculations to time domain simulations, from linearized to nonlinear boundary conditions, and from small wave amplitudes to breaking waves, spray, and water flowing onto and off the ship’s deck. Frequency domain methods have been widely used as strip theories (2D) or as panel methods (3D) with different levels of nonlinearities considered in the mathematical model They are valid under small wave amplitudes and small ship motions hypothesis, assuming linearized boundary conditions and the linear superposition principle. Simulations are performed with the time step equal to the frequency of sampling, and an identical analysis of the numerical and experimental time series is performed to obtain the fair comparison
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