Course content

The course concerns seakeeping and stationkeeping and deals with displacement ships and offshore structures. The sea environment is characterized in terms of waves, wind and current. The loads and/or motions induced on the marine structures are examined as linear, second and higher-order wave effects, within potential-flow theory, and viscous wave, current and wind effects. Emphasis is given to the mean and slowly-varying motions in waves, wind and currents. Occurrence, features and consequences of vortex induced oscillations are also discussed. Procedures for the loads/motions estimates are provided. Cancellation effects and motion control are also discussed. This includes anti-roll devices for ships and dynamic positioning for offshore platforms. Fully nonlinear phenomena connected to the wave-body interactions are analyzed in terms of slamming, water-entry and water-exit. The course provides information both on simplified methods and on experimental techniques for the seakeeping.

Learning outcome

Main objectives of the course are:
- To provide insights on critical problems at sea for a given marine structure, the relevant response variables and the related safety/operational criteria.
- To build up knowledge on orders of magnitude for design environment conditions, structure natural periods and resonant and unstable motions.
- To generate physical understanding of the phenomena connected with the fluid-structure interaction problems of practical interest and to make use of simple methods for an early design stage, for marine operation planning or for checking practical computer results or model experiments.

Among the learning outcomes for the students, with respect to knowledge and skills, one can list:
- To be able to identify critical environmental and operational conditions for standard ships and offshore structures.
- To be able to estimate relevant response variables (motions, relative motions, accelerations, etc.) within linear theory and assess safety and operational limit criteria for the specific marine unit.
- To understand how to estimate second-order effects in the loads, i.e. mean, difference-frequency and sum-frequency effects caused by wave-body interactions and to know the limit of applicability of the approximated approaches. To learn how to estimate added-resistance in short waves and to know the major sources of slow-drift damping.
- To be able to estimate the slowly-varying loads connected with wind gust, the mean and oscillatory loads connected with current (and wind), the effect of wake interactions using a simplified wake solution.
- To be able to check possible occurrence of VIV and to know the related consequences in terms of vortex-shedding frequency, natural frequency of the structure and oscillation amplitude. To know the difference between VIV and galloping and occurrence of the latter.
- To know the features and consequences of stationkeeping, the factors reducing performances of thrusters and the challenges in building up a proper dynamic positioning.
- To be able to roughly assess occurrence of water on deck and slamming and to know the physical phenomena and factors connected with slamming, its relevance and consequences. To learn the general features of the major methods used to predict slamming loads on vessels and to check slamming operational criteria.

Learning methods and activities

Lectures and compulsory exercises. 8/12 exercises must be accepted for admission to the final exam. Postponed/repeated exams may be oral. Examination papers will be given in English only. Students are free to choose Norwegian or English for written assessments.

Compulsory assignments

• Exercises

Recommended previous knowledge

TMR4247 Marine Technology - Hydrodynamics.

Course materials

O.M.Faltinsen: Sea Loads on Ships and Offshore Structures, Cambridge University Press, 1990.

Credit reductions