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To investigate the parametric rolling motion of container ships navigating in head seas, this study utilizes the unsteady RANS approach combined with dynamic overlapping grid technology to simulate parametric roll in a container ship under the coupled motions of roll, pitch, and heave. Initially, the model was validated against experimental results, demonstrating good agreement and thus confirming the reliability of the computational method. Furthermore, the paper investigates the impacts of the initial roll angle, encounter frequency, and the addition of bilge keels on parametric rolling. The research findings indicate that the initial angles of rolling impact the duration needed to attain a steady roll condition, yet they have minimal effect on the amplitude post-stabilization. The likelihood of parametric rolling arises when the frequency of encounters doubles that of the ship’s inherent roll frequency. Furthermore, the likelihood of parametric rolling escalates when the wavelengths approach the length of the ship. Installing bilge keels markedly reduces the parametric rolling movement in vessels, and the occurrence of parametric rolling is also delayed.

Gong, J.; Li, Y.; Jiang, F.; Hong, Z., and Yu, D., 2020. Maneuvering simulation and study on the effect of hull attitude on maneuverability of trimarans by OpenFOAM. Journal of Coastal Research, 36(1), 157–173. Coconut Creek (Florida), ISSN 0749-0208. Based on open-source code OpenFOAM, the turn and zigzag maneuvers of the trimaran with hull attitude free and fixed are simulated at different Froude numbers in calm water. By the simulation results, the effect of hull attitude on the maneuver characteristics of the trimaran is analyzed and discussed. Two trimaran models are used in this paper for simulation. First, the grid uncertainty test about the turn and zigzag maneuver in calm water is carried out, and the computed results of turn and zigzag maneuvers in calm water are compared with the experimental results to validate the numerical method. Then, the simulation result with free hull attitude is compared with that with fixed hull attitude. The result demonstrates that the hull attitude has significant effect on the maneuverability of the trimaran, especially when the Froude number gets larger and the longitudinal position of the side hulls is in the middle of the center hull. [ABSTRACT FROM AUTHOR]

Torsional motion is an important motion state to Trimaran caused by the significant coupled motion between pitch and roll. Based on viscous flow theory, the present research predicts the motion of Trimaran in oblique wave conditions by the open-sourced CFD code OpenFOAM. The torsional motion states of Trimaran are analyzed based on the numerical results. Three kinds of coupled motion have been classed, and the motion characteristic of each motion state is studied. On this basis, the most dangerous reciprocated coupled motion has been studied emphatically. Furthermore, the coupled motion states of Trimaran are analyzed in oblique head wave s and oblique stern wave, respectively. The results of the research shows that torsional motion states is more easily to occur in oblique head seas. Especially in high frequency wave conditions, the motion state is prone to dangerous reciprocating coupled motion. The analysis of motion characteristics is significant to trimaran's hydrodynamic research and the vessel's navigation safety. • New analysis methods have been used to find out the real navigation states about trimaran's torsional motion. • Different kinds of coupled motion have been classed. The characteristics of different motion states have been analyzed. • Some dangerous trosional states of trimaran in different wave heading conditions are analyzed respectively. [ABSTRACT FROM AUTHOR]

Trimaran added resistance and seakeeping performance in oblique waves with strong nonlinearity are rarely investigated. This paper presents the numerical investigations on them by applying a hybrid method, called the QaleFOAM. This method can simulate a trimaran moving in a large wave field, considering viscous effects and dealing with violent wave-structure interaction (WSI). The numerical method is validated by experimental data for a trimaran moving in waves. Various cases are investigated with different wave steepness, different wavelengths, different forward speeds and different wave incident angles to study the properties and characteristics of the added resistance and seakeeping performance of a trimaran. The results demonstrate that the variational trend of the added resistance and motion amplitudes of the trimaran in waves is significantly affected by the wave steepness and wave incident angles and different from those of traditional mono-hull ships. • A systematic study on the added resistance/seakeeping performance of trimarans in oblique waves of different parameters. • Directly modelling the advancing of the trimaran in waves by using a robust hybrid model, QaleFOAM. • The added resistance and motion amplitudes of the trimaran are significantly affected by the wave steepness and wave incident angles. • Two approaches (directly modelling or inputting ship speed and waves at inlet) for forward ship in waves leading to considerable difference. [ABSTRACT FROM AUTHOR]

Coupled motion is an important factor that affects the safety and stability of ships sailing in waves, especially for rolling coupled with pitch motion. This paper simulates the motions of trimaran in waves and analyzes the motion characters. The open sourced CFD code OpenFOAM is used to predict the trimaran's motions in oblique head waves, oblique stern waves and beam waves. The grid convergence analysis and the comparison with experimental results are carried out to verify the numerical method. Focusing on the coupled motion characteristics and the stability of trimaran under different waves, a comparative analysis of the trimaran's motion state is made. The changing laws of coupled motion characteristics with different forward speed, wave steepness, wavelength and wave headings are studied. The results show that the trimaran has the largest coupled motion of rolling and pitch in the oblique head waves, but the motion is relatively regular and stable; the trimaran has a relatively poor performance in several wave conditions of oblique stern waves and beam waves. Some wave conditions are easily to cause the unstable rolling motion, especially in small wavelength conditions. 1. The research studies trimarans' coupled motion characteristics based on CFD method, which is different with the study method used by other researchers before, such as multi scale perturbation analysis or Taylor expansion method of the coupled factor in motion equations. The CFD results can describe the motion states more intuitively than the frequency domain methods. 2. The research studies the important roll-pitch coupled motion states of trimaran which is important to the vessel because of the existence of side hulls. While the phenomenon has not been studied by the previous researches. 3. The rolling stability of trimaran is compared at different wave headings based on the CFD results. At this point, some good sailing navigation strategies have been given. [ABSTRACT FROM AUTHOR]