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Ship maneuvering in waves is analyzed by using a unified seakeeping and maneuvering two-time scale model in irregular sea that has been applied by Skejic and Faltinsen [1] for regular waves. The irregular wave effects are accounted for by Newman’s [2] approximation of the slow-drift 2nd order wave loads valid for deep water (Faltinsen [3], Pinkster [29]). The modular type maneuvering model (MMG model) based on Söding’s [4] nonlinear slender-body theory is used for the maneuvering analysis. Forces and moments due to rudder, propeller, and viscous cross-flow are accounted for as presented by Skejic and Faltinsen [1] and Yasukawa [5, 6]. In particular, the behavior of the propulsive coefficients (the thrust deduction and wake fraction) in waves (Faltinsen et al. [7], Faltinsen and Minsaas [8]) are discussed from the perspective of ship maneuvering characteristics in both regular and irregular wave environments. The unified model of seakeeping and maneuvering for deep-water irregular waves is validated for the ‘S7-175’ (‘SR 108’) container ship in calm water and regular deep-water wave scenarios by comparison with experimental results by Yasukawa [5, 6]. The maneuvering model is applied to a ‘MARINER’ ship performing turning maneuver in irregular waves. The obtained results of the ships main maneuvering parameters are discussed from a statistical point of view.

Hydrodynamic interaction effects between two ships going ahead in regular deepwater waves were numerically studied during typical maneuvers for ship-to-ship (STS) operations, such as lightering, replenishment, etc. Such maneuvers are usually classified as potentially hazardous situations, due to the possibility of collision between the two vessels when they are operating in close proximity. Since the collision hazard is usually even greater in bad weather conditions, knowledge of the maneuvering capabilities of two ships in a seaway must be available in order to ensure safe and efficient STS operation. In this study, a combined seakeeping and maneuvering analysis of two ships involved in typical lightering operation was performed using a unified seakeeping and maneuvering theory developed by Skejic and Faltinsen [1, 2]. The unified theory integrates seakeeping and maneuvering analysis by using a two time scale assumption and modular concept. This approach allows the maneuvering behavior of the two ships involved in lightering operation in waves to be successfully described. The seakeeping analysis for both vessels uses Salvesen-Tuck-Faltinsen [3] (STF) strip theory for deep water by assuming that there are no hydrodynamic interaction in waves between the two ships. The regular wave field effects upon the involved vessels are described by the mean second-order wave loads. They can be estimated by using one of the available near/far field theories (Salvesen [4] and Faltinsen et al. [5]) that take the complete wave length range of interest for a considered STS maneuver into account. When the incident wave length is short relative to the ship length, the asymptotic theory by Faltinsen et al. [5] is used. The predicted mean second-order wave loads according to these theories are shown in the case of turning maneuver of a ‘MARINER’ type of a ship in specific wave conditions. The maneuvering module of the unified theory model is based on generalized slender-body theory, while calm-water interaction forces and moments between the two ships are estimated using Newman and Tuck [6] theory. Automatic steering- and speed-control algorithms for both ships (Skejic et al. [7]) are employed to achieve high-precision and collision-free lightering maneuvers in waves. This is illustrated by a numerical simulation involving ‘Aframax’ and ‘KVLCC’ (type 2 – Moeri tanker [16]) types of ships. Finally, from the perspective of marine safety and reliability, the future requirements and recommendations for typical lightering operations in a seaway are discussed.

The present study is focused on performance issues of underwater vehicles near the free surface and gives insight into the analysis of a speed loss in regular deep water waves. Predictions of the speed loss are based on the evaluation of the total resistance and effective power in calm water and preselected regular wave fields w.r.t. the non-dimensional wave to body length ratio. It has been assumed that the water is sufficiently deep and that the vehicle is operating in a range of small to moderate Froude numbers by moving forward on a straight-line course with a defined encounter angle of incident regular waves. A modified version of the Doctors & Days [1] method as presented in Skejic and Jullumstrø [2] is used for the determination of the total resistance and consequently the effective power. In particular, the wave-making resistance is estimated by using different approaches covering simplified methods, i.e. Michell’s thin ship theory with the inclusion of viscosity effects Tuck [3] and Lazauskas [4] as well as boundary element methods, i.e. 3D Rankine source calculations according to Hess and Smith [5]. These methods are based on the linear potential fluid flow and are compared to fully viscous finite volume methods for selected geometries. The wave resistance models are verified and validated by published data of a prolate spheroid and one appropriate axisymmetric submarine model. Added resistance in regular deep water waves is obtained through evaluation of the surge mean second-order wave load. For this purpose, two different theoretical models based on potential flow theory are used: Loukakis and Sclavounos [6] and Salvesen et. al. [7]. The considered theories cover the whole range of important wavelengths for an underwater vehicle advancing in close proximity to the free surface. Comparisons between the outlined wave load theories and available theoretical and experimental data were carried out for a submerged submarine and a horizontal cylinder. Finally, the effective power and speed loss are discussed from a submarine operational point of view where the mentioned parameters directly influence mission requirements in a seaway. All presented results are carried out from the perspective of accuracy and efficiency within common engineering practice. By concluding current investigations in regular waves an outlook will be drawn to the application of advancing underwater vehicles in more realistic sea conditions.