The settling dynamics of a non-spherical particle in fluids are ubiquitous in both natural and industrial processes, and the underlying mechanisms are considerably more complex than those of a traditional spherical particle. This study employs high-fidelity numerical simulations to systematically investigate the coupled effects of aspect ratio (γ = 1.00–2.00) and initial inclination angle (0°–90°) on the settling behavior of an ellipsoidal particle within an intermediate Galileo (Ga: 120–220) regime. The results reveal the existence of a critical Ga (Gacrit) that marks the transition of the flow regime from a steady state to a periodic unsteady state. Furthermore, the particle aspect ratio is identified as the key parameter governing the modes of stability and instability. Spherical and near-spherical particles destabilize first, leading to regular two-dimensional vortex shedding. In contrast, elongated particles, benefiting from shape-induced drag, demonstrate superior stability and a significantly higher Gacrit. Within the investigated Ga range, pressure drag accounts for more than 85% of the total drag during particle settling, and its dominance becomes more pronounced with increasing Ga. More importantly, in the chaotic regime, the initial inclination angle acts as a critical bifurcation parameter that can trigger distinctly different final states, including steady settling, two-dimensional oscillation, or three-dimensional tumbling.

Sloshing poses significant risks to the structural integrity, stability, and maneuverability of marine vessels. This study employs an enhanced moving particle semi-implicit method to investigate sloshing in a partially filled tank equipped with a constrained floating baffle. The baffle length ratio Lb/L is varied from 0 to 0.6, and the free-surface elevation, wall pressure, and tank lateral force are examined from the initial transient to the quasi-steady regime. Power spectral density, phase-resolved vorticity fields, and energy histories are further analyzed to characterize the dominant-mode response and the underlying dissipation mechanisms. The results reveal a nonlinear saturation with increasing baffle length: the primary resonant response decreases markedly as Lb/L increases. However, under the present excitation and filling conditions, when Lb/L reaches a certain range of approximately 0.45–0.55, the marginal suppression becomes limited, indicating a threshold-like behavior in the mitigation effect of the constrained floating baffle. The mechanistic evidence indicates that the baffle enhances localized shear and vortex activity in its vicinity, causing vortex interaction and breakup during flow reversal and thereby weakening the phase-coherent momentum feedback that sustains the primary sloshing mode. Consequently, both the dominant spectral component and the impact-related pressure fluctuations are reduced, leading to lower hydrodynamic loads. These findings clarify the dissipation mechanism of constrained floating baffles and provide useful guidance for anti-sloshing design in partially filled tanks.

The lift force of a T-foil, which varies with ship motion, can counteract the wave exciting force during wave encounters. The phase difference between the periodic lift force and the wave exciting force significantly impacts the T-foil’s effectiveness. This study investigates the phase difference between lift force and motion to optimize the control equation for the T-foil’s angle, thereby reducing negative feedback. The T-foil’s hydrodynamic performance is first calculated using computational fluid dynamics. Time-domain calculations of the phase lag between lift force and motion under open-loop control in still water are then used to determine the dimensionless phase lag of the T-foil’s angle at various frequencies, facilitating further optimization of the control method. Finally, calculations of trimaran heave and pitch in regular waves are conducted. The results demonstrate that, under phase lag control, the T-foil’s lift force phase precedes ship motion by approximately 0.2 s, reducing hysteresis in the anti-vertical motion effect. Comparisons of vertical hull motions between different control methods reveal a 20% reduction in vertical motion with phase lag control compared to pitch control. This study concludes that phase lag is a crucial factor in T-foil control optimization.