Physics-based analysis of accelerating turning maneuver of ships via high-fidelity numerical simulations

The accelerating turning maneuver represents a critical transition where a vessel must simultaneously overcome its longitudinal inertia and establish a stable yaw rate, a high-load state that triggers significantly more complex hull-propeller-rudder interactions than those found in the quasi-steady phase of a standard turning circle. This paper presents a physics-based assessment of naval ship turning performance under both steady and transient conditions by means of fully free-running, six-degrees-of-freedom computational fluid dynamics simulations of a surface combatant. Turning Circle and Accelerating Turning (turning from rest) maneuvers are analyzed within the same numerical framework, including twin rotating propellers, active rudders, free-surface effects, and full hull–propeller–rudder interaction. The results show that, although the two maneuvers converge to similar steady yaw rates, their transient evolution differs substantially, leading to pronounced discrepancies in advance, roll response, and, most notably, the time required to achieve a prescribed heading change. These differences directly affect compliance with NATO STANAG (North Atlantic Treaty Organization Standardization Agreement) 4721 requirements, demonstrating that maneuvering performance governed by transient acceleration effects cannot be reliably inferred from conventional steady-speed turning circle tests. By resolving the full transient dynamics from rest to steady turning and quantifying the associated numerical uncertainty, the study highlights the necessity of transient-resolved CFD for standards-based maneuvering assessment and for the development and validation of predictive and control-oriented maneuvering models.