AIMS AND LEARNING OUTCOMES

The class aims to provide the student with the theoretical physical-mathematical backgrounds and the necessary tools for the evaluation and analysis of the dynamics of the ship that is advancing at sea, i.e. of the ship's response to a random sea. Such a response, in the context of the linear theory of seakeeping, will be identified by means of suitable response operators of displacements, velocities, accelerations and wave loads.

To this end, notions relating to the modeling of irregular waves and sea (regular waves, hull waves, random sea patterns) will be introduced during the course, as well as to the modeling of the response of a generic hull that can move in six degrees of freedom.

At the end of the class the student will then be able to understand and apply different theories concerning both the various themes considered individually (e.g. waves, sea, hull), and the overall response of the ship in a random sea.

TEACHING METHODS

Lectures in the classroom. Homeworks may be carried out on specific topics chosen during the class.

SYLLABUS/CONTENT

In the following, the essential contents of the class are inroduced.

1) REGULAR WAVES: Stationary and progressive waves. Dispersion relation. Energy and wave group. Validity fields of theories. Cylindrical waves coming from prescribed direction. Equation of waves related to a moving system, frequency of encounter. Overlapping cylindrical waves.

2) IRREGULAR SEA: Review of the random functions over time. Spectrum of the sea. Model of the mono- and multi-directional sea state. Parametric spectra.

3)  WAVES GENERATED BY THE HULL AND WAVE RESISTANCE: Stationary wave fields generated by the motion of the hull in still water. Effect of bottom depth. Wave resistance from the wave field. Spectra of free waves.

4) MOTIONS OF THE SHIP: Definition of reference systems and motions. Forces due to ship motions and waves. Equations of ship motions and their linearization. Hydrodynamic problems related to ship motions. Effect of the speed on the ship motions. Bi- and tri-dimensional methods for evaluating ship motions. Longitudinal motions and transverse motions.

5) SHIP RESPONSE TO REGULAR WAVES: Linear motions and response amplitude operators. Response amplitude operators of motions, accelerations, relative motions and speeds. Wave loads. Wave shear force and bending moment.

6) SHIP RESPONSE TO IRREGULAR WAVES: The spectrum of response and short-term statistics.

RECOMMENDED READING/BIBLIOGRAPHY

1) E.V. Lewis (1988). Principles of Naval Architecture Volume III: motion in waves and controllability. SNAME.

2) Larsson, L., & Raven, H. C. (2010). Ship resistance and flow (Principles of naval architecture series). Alexandria, VA: SNAME.

3) Lloyd, A. R. J. M. (1989). Seakeeping: ship behaviour in rough weather. Ellis Horwood.

4) Newman, J. N. (2018). Marine hydrodynamics. MIT press.

5) Lewandowski, E. M. (2004). The dynamics of marine craft: maneuvering and seakeeping (Vol. 22). World scientific.

6) NABERGOJ, R. (2007). Fondamenti di tenuta della nave al mare. Università di Trieste, Trieste.