The course considers the three main categories of high-speed vessels, i.e. hull-supported, air-cushion supported and foil supported vessels. Hull-supported vessels are divided into semi-displacement and planing vessels. All hydrodynamic aspects are discussed. This means resistance, trim, wash, propulsion, seakeeping, hydrodynamic stability and maneuvering. Links to automatic control and structural mechanics are emphasized. It is important to stress that methods/topics treated by the course can be applied to/are relevant for displacement vessels, as a special case of hull-supported vessels operating in the low Froude-number range.
The driving questions are: What are the resistance components of different high-speed vessels? What are their seakeeping and maneuvering properties? What are the main instability mechanisms/phenomena as a function of speed? Which prediction methods are suitable to predict their equilibrium conditions, their calm-water performances, their operations at sea?
The main steps of the course are the following. First, a general overview of the course is given. Then, the different high-speed vessel categories are examined in detail. The surface effect ships (SES), dealing with: static equilibrium, metacentric height, resistance components, air bag, bow seal, speed loss in waves, cobblestone oscillations. The hydrofoil vessels, dealing with: static equilibrium, lift and drag coefficients, cavitation, from hullborne to foilborne conditions, resistance, manoeuvring, automatic control, linear foil theory, Weissinger approximation, three-dimensional foil theory, free surface effects, foil interaction, wave induced motions of hydrofoil vessels. The semi-displacement vessels, dealing with: resistance components, wave resistance and wash, wave induced motions, added resistance, dynamic stability, global wave loads, manoeuvring. The planing vessels, dealing with: steady equilibrium, dynamic instability. porpoising. manoeuvring.
TMR4215 Sea Loads.
General objectives of the course are:
- To build up knowledge about different types of high-speed vehicles, their typical applications, and their hydrodynamic features.
- To provide enough physical insight to interpret theoretical and experimental investigations of hydrodynamic properties applied in design of high-speed marine vehicles.
- To unable performing simple analyses and calculations of hydrodynamic properties of high-speed marine vehicles.
- To master the concepts and terminology of high-speed marine vehicles.
Among the learning outcomes for the students, with respect to knowledge and skills, one can list:
- To understand the key differences between alternative high-speed vessel concepts, their design and operation advantages and challenges; this is essential in order to select a specific concept for targeted missions.
- To learn the relative importance of physical mechanisms in the resistance experienced by a high-speed vessel in calm water and to be able to estimate it by choosing the suitable prediction methods. To be able to estimate added-resistance contributions due to e.g. interaction with incident waves, maneuvering.
- To be able to identify the appropriate propulsion system for a specific high-speed vehicle and to estimate, for propellers and water jets, the provided thrust and the efficiency, as well as to be able to control their operative challenges.
- To be able to estimate relevant wave-induced response variables (motions, relative motions, accelerations, etc.) within linear theory and assess operational limit criteria for a specific high-speed vessel. This includes also the estimation of occurrence and features of rigid-motion resonance and flexible-mode resonance (springing/whipping).
- To be able to roughly assess occurrence of violent wave-body interaction phenomena, such as 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 their local and global consequences.
- To be able to estimate the hydrodynamic loads during ship maneuvering as well as the loads and performance of the steering devices, including maneuvering in waves, presence of other ships or structures.
- To be able to assess static and dynamic stability of high-speed vehicles and to identify relevant design and operational parameters governing their stability properties.
- To be able to examine the use of automatic control and its consequences for the vessel behavior.
- To be aware of scaling issues when performing model tests to estimate relevant local/global variables for different high-speed vessels.