Abstract
For all design phases of naval vessels, the fidelity of seakeeping calculations in extreme seas is open to discussion due to the inadequacy of the linear theory of ship motions. Currently the computer-generated time series of ship responses and wave height (the real time computer experiments) are utilized to calculate the distribution of the vertical distortion, shear force and bending moment by means of “ship hydroelasticity theory”. Inspired by these studies a simulation based calculation of symmetric ship motions is performed in long crested irregular head seas, in addition with a body-exact strip theory approach. The scope of this study is limited to the ship motions only. Verification is achieved utilizing the spectral analysis procedure which contains the discrete Fourier transform (DFT) and the smoothing algorithms. The results are compared with the experimental data, and the ANSYS AQWA software results. The simulation results provide adequate data for the extreme responses. This state-of-the-art method in addition with a “body-exact strip theory approach” ensures the consistent assessment of the seakeeping performance in extreme sea condition. As a result, it is evaluated that this calculation method can be used in the design stages of naval platforms.
Highlights
Ship designers aware of that the linear theory is not sufficient for ship motion calculations in extreme seas
Reliability of the ship motion calculations is important for the design and verification of the ship itself and the systems on board
The spectral density functions and the corresponding Response Amplitude Operators (RAOs) derived from the “body-linear” and “body-exact” time series data with spectral analysis procedure were compared with the calculated spectra and RAOs by the linear theory in frequency domain
Summary
Ship designers aware of that the linear theory is not sufficient for ship motion calculations in extreme seas. It is aimed to use a similar approach to the non-linear strip theory extensions, which are faster than the 3D solution In this context, as cited in STANAG 4154 [1], studies carried out by Kaplan and Sargent [5], Mansour and d’Oliveira [6] (The computer program ADMASS for the frequency-dependent added mass calculation), Meyerhoff and Schlachter [7], Schlachter [8]&[9] (The computer program DYNBEL) and Guedes Soares [10] on the vertical plane; studies carried out by De Kat [11]&[12] and De Kat and Paulling [13] on the six degrees of freedom are first coming to the forefront. As clarified by Belik [21] and Newland [28], the discrete Fourier transform (DFT) and smoothing algorithms are utilized for the verification and comparison of the simulated data with the experimental data [29], and the ANSYS AQWA software results of Çekirdekçi [30]
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