Prof. P. Ferrant
Code = EMSHIP S3-2 (Semester 3)
Workload: lectures (20h), practical training (15h)
Number of credits: 5
Objective:
The objective here is to give a complete presentation of the available models for the determination of the ship’s response in a seaway, emphasizing the advantages and drawbacks of each approach.
First, we give a complete presentation of the linearized theory of wave-body interactions, treated in a deterministic sense. Both frequency domain and time domain approaches are described. Fundamental relations between both solutions are systematically emphasized. High and low frequency second order effects are explained and illustrated.
Then, an overview of the available nonlinear theories of seakeeping is given. Different levels of approximation are described, from the simple addition of nonlinear hydrostatics to fully nonlinear time domain models.
In addition to the theoretical part, practical exercises are proposed to the students, based on some typical state of the art numerical software for ship seakeeping.
Contents:
• Objectives, theoretical frame
• Short review of linear systems theory
• Formulation of the boundary value problem. Linearization
• Frequency domain approach
o Definition of diffraction and radiation sub-problems
o Hydrodynamic loads: added mass and damping
- Calculation of motions
- Relations between elementary solutions
• Time domain approach
oForced motion of a floating body
o Formulation of the diffraction problem in the time domain
o Equations of motion
o Relation to frequency domain response
• Second order effects:
o Drift forces
o Low and high frequency loading in irregular waves
• Introduction to Nonlinear Models for Ship Seakeeping
o Nonlinear Hydrostatics and Froude-Krylov loading
o Weak scattered hypothesis
• Fully nonlinear approaches
• Practical use of numerical tools dedicated to ship seakeeping under potential flow theory. Meshing; convergence studies; Influence of non linear effects; comparisons with results from the literature; discussion; advantages and drawbacks of the model.
Recommended reading:
“Sea Loads on Ships and Offshore Structures” by O.M. Faltinsen, Cambridge ocean technology series.
Prerequisites:
Elements on water waves modelling given in the EMSHIP S2-1 lecture described before will be useful here.
Form of exams:
Written exam (1h)+ report of practical training.