Examination arrangement

Course content

The course concerns the behavior at sea of standard ships (seakeeping) and offshore structures (stationkeeping) and the assessment of relevant design and operational criteria for a successful activity of the examined marine unit. A driving question is: How can we ensure safe, effective and efficient marine activities? This leads to complementary questions such as: What is the relevant sea environment for an examined marine unit? How can we classify the sea loads and motions induced on the marine structure in terms of nonlinearities and physical phenomena involved? Which prediction methods can be used? What are their applicability regions and reliability limits? The main steps of the course are the following. First, the sea environment is characterized in terms of waves, wind and currents.The loads and/or motions induced on the marine structures are examined as linear, second and higher-order wave effects, within potential-flow theory. Then, viscous effects connected with steady current and wind and/or with waves are studied. Occurrence, features and consequences of vortex induced oscillations and of galloping are discussed. Emphasis is given to the mean and slowly-varying motions in waves, wind and currents. They are important for the stationkeeping of marine structures. In this context design and challenges of dynamic positioning are discussed. Finally, fully nonlinear phenomena connected to the wave-body interactions are analyzed in terms of slamming, water-entry and water-exit. In the aim to increase the vessels operability, the course will examine how to minimize wave induced motions by passive and active tools.This includes anti-roll devices for ships and dynamic positioning for offshore platforms. In the aim to propose relevant prediction methods for the seakeeping, the course provides information both on simplified methods and on experimental techniques.

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, ie 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 the 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. 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 the 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. 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 the 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. - To be able to roughly assess the 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. - To be able to roughly assess the 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: There are a two-plus-two hours theoretical and a two-hour exercise lectures per week. The students are advised to follow all lectures; this will help them in the learning process and will encourage a good learning environment with the other students. At the exercise lectures they will receive hints for the specific exercise and help to improve their solution-strategy skills. Two/three student assistants will help the students with the exercises and a PhD student will administrate the exercise lectures and activities. Assignments: During the course, exercise lectures will alternate with the theoretical lectures. Each week, exercises will be assigned to the students with topics which are within the scope of the course and related with the course learning program. The deadline is two weeks after each assignment. In total, twelve exercise home-works will be assigned concerning problems relevant for the course content and scope. The exercises must be submitted in time in order to be considered for the exam requirements. Exceptions can be done if delays are suitably justified. Learning assessment: At the beginning of the course, a list of sample questions closely connected with the theoretical lectures, are provided to the students. The students are advised to check their capability in answering the questions in the meanwhile that they follow the course and to notify if they encounter any difficulty. They are also advised to work in groups to examine the questions from different perspectives and open their minds using the different students’ backgrounds as enrichment for their learning activities. Communications: All information of the course is provided through the Online Learning Platform of the course. This includes the exams from previous years, the topics of the course split in theoretical and exercise lectures, the lecture notes and slides from the theoretical lectures, the sample questions, the assigned exercises. The students can also upload their home-works on the same Online Learning Platform and are informed of specific changes/matters through bulletins.

Compulsory assignments

• Exercises

Further on evaluation

Eight of the twelve assigned exercises must be accepted for admission to the final exam. Examination material will be given in English only. The assessment is based on a final exam counting for 100% of the grade.

Postponed/repeated exams may be oral. For a re-take of an examination, all assessments during the course must be re-taken.

Recommended previous knowledge

TMR4247 Marine Technology - Hydrodynamics.

TMR4182 - Marine Dynamics

Required previous knowledge

Familiarity with mathematical symbols and to have basic knowledge of fluid mechanics, water waves, and hydrodynamics.

Course materials

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

Credit reductions