Numerical investigations on seakeeping and added resistance in head waves based on nonlinear potential flow methods

• Published in: Ocean engineering Vol. 276; p. 114043
• Main Authors: Zhang, Xinshu, Song, Xingyu, Beck, Robert F.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.05.2023
• Subjects: Added resistance; Body-exact method; Desingularized source; Fully nonlinear potential flow method; Seakeeping; Fully nonlinear potential flow method; Body-exact method; Added resistance; Seakeeping; Desingularized source
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2023.114043

A fully nonlinear potential flow (FNPF) method and a body-exact (BE) method based on the time-domain desingularized-Rankine panel (DRP) method have been developed to compute the motion responses and added resistance for ships traveling in regular head waves. In the present methods, the disturbed wave potential is separated from the incident potential, and the boundary value problem (BVP) for the disturbed potential is established in each method. To validate the present FNPF and BE methods, different hull forms are adopted, including two Wigley hulls and the S-175 containership. The results of radiation, diffraction, and free motion simulations are presented and systematically compared with the experimental data and linear solutions using the double-body (DB) and Neumann–Kelvin (NK) methods. Through comparison, we demonstrate that the present FNPF method can accurately predict the motion responses and added resistance of ships. For the ships with large flare angles, the FNPF and BE methods give better predictions of peak motion responses than those using DB and NK. In addition, the FNPF method can well predict the added resistance, and has significant advantages over the other numerical methods at high forward speed (Fn=0.3). The analyses also confirm that, compared with the heave and pitch motions, the added resistance and the total wave elevations are more sensitive to the incident wave amplitude. The dimensionless added resistance decreases with the increase of incident wave amplitude, which is mainly driven by the total wave elevations along the waterline in the bow region. As the incident wave amplitude increases, the 1st harmonic amplitudes of the heave and pitch motions and the total wave elevations in the bow region decrease, while the 2nd harmonic amplitudes increase. •A fully nonlinear potential flow method is developed for added resistance computations.•A body-exact method is developed for added resistance computations.•The NURBS curves are adopted for the updating of mesh discretization.•The nonlinear effects of the incident wave amplitude on added resistance are analyzed.