OVERVIEW

This unit provides an overwiew on the hydrodynamic design of motor yachts, focusing on high speed crafts. The topic will be addressed focusing firstly on hull performances, secondly on aspects concerning propulsions.  Concerning the first topic, significant part of the course will address the hydrodynamics of planing hulls and available method to assess their performances during preliminary design: Savitsky method, systematic series, statistical methods and model tests.

Additionally, aspects of the hydrodynamics of stepped hulls and hydrofoil vessels will be discussed. 

The last part of the course will instead address specific aspects of the propulsion of high speed applications, such as propeller cavitation and surface piercing propellers.

As a result this unit aims to complete the students knowledge in the field of naval architecture and hydrodynamic design of yachts considering theories and methods specifically dedicated to high speed applications. 

AIMS AND CONTENT

LEARNING OUTCOMES

The teaching aims to complete the student skills in the naval architecture field through the study of advanced topics specifically concerning the preliminary phase of the design.

AIMS AND LEARNING OUTCOMES

• Understand the hydrodynamics of planing hulls with a focus on the effects of main parameters (e.g. main dimensions, loading condition, velocity) on the resistance. 
• Apply the Savitsky method to predict planing hull resistance and dynamic trim.
• Remember the theoretical basis for the use of towing tank tests, systematic series and statistical methods, with a special focus on high speed crafts.
• Understand the hydrodynamics of stepped hulls and hydrofoil vessels, along with main aspects concerning their hydrodynamic design. 
• Remember the theoretical basis for the sizing of the propulsion system of an high speed marine vehicule.
• Remember theoretical basis of cavitation.
• Understand methods to address cavitation issues during early design of a high speed craft.
• Understand the functioning of surface piercing propellers and the use of relevant systematic series for their preliminary design.

PREREQUISITES

There are no specific requirements

TEACHING METHODS

Lectures (about 48 hours) and practical excercise on the Savitsky method (about 4 hours).

Students with valid certifications for Specific Learning Disorders (SLDs), disabilities or other educational needs are invited to contact the teacher and the School's disability liaison at the beginning of teaching to agree on possible teaching arrangements that, while respecting the teaching objectives, take into account individual learning patterns.

SYLLABUS/CONTENT

Introduction

• Hull typologies: Displacing, semi-displacing and planing hulls
•   Resistance of a vessel
  •    Displacing hull (recap)
  •    Planing hulls

Planing hull geometry and definitions

The Savitsky method

• Introduction of the Savitsky model
• Geometry of the Savitsky model
•  Hydrodynamic of a flat planing surface
•   hydrodynamic of V-shaped planing surface

 Planing hull lift

•     Dynamic lift
•     Hydrostatic lift
•     V-shaped hull

  Planing hull resistance

• Ideal fluid
• Real fluid and friction drag
• Effect of trim on planing hull resistance

Centre of Pressure

Equilibrium equations and their solution

Simplified Savitsky method

Extension of the Savitsky method

Additional resistance components

• Appendages resistance
• Spray resistance 
• Air resistance

Trim control

• Design options
• Active devices

Implementation and application of the Savitsky method (assignment)

Stepped hulls

• Functioning principle
• Step configurations
• Flow field downstream of a planing hull
• Methods for the design and/or the performance prediction of stepped hulls

Hydrofoil vessels

• Functioning principle
• Lift and drag of a 2-D foil
• 3-D effects on the lift and drag of a finite span hydrofoil
• Hints about equilibrium of hydrofoil vessels
• Main characteristics of hydrofoil vessels
• Hydrofoils configuration

Towing tank tests of high speed marine vehicles

• Recap on towing tests for ships
• Preparation of the model
• Experimental setup
• Measured quantities
• Full scale extrapolation

Systematic series for high speed crafts

The second VTT statistical method for planing hulls resistance

Dynamic stability

• Types of instability
• Transverse stability
• Longitudinal stability (porpoising)

Propulsion of high speed crafts

• General principles
• Cavitations
  • Cavitation types and effects
  • Thrust and torque breakdown
  • Systematic series of cavitating propellers
• Surface Piercing Propellers (SPPs)
  • Functioning principle
  • Performances of SPPs
  • Systematic series of SPPs
  • Typical design issues

RECOMMENDED READING/BIBLIOGRAPHY

Lecture notes are available on the website:

https://ingsp.aulaweb.unige.it/

The following texts are suggested for further readings:

Principles of Naval Architecture, SNAME, 1988

SAVITSKY D. “Hydrodynamic Design of Planing Hulls”, Marine Technology, October 1964.

Blount D. L., Fox D.L. “Small Craft Power Prediction”, Marine Technology, Vol. 13, No. 1, Jan 1976.

Savitsky D., Brown P.W. “Procedures for Hydrodynamic Evaluation of Planing Hulls in Smooth and Rough Water”, SNAME, Hampton Road Section paper, November 1975.

Hadler J.B. “The Prediction of Power Performance on Planing Craft”, SNAME Transactions, 1966.

Faltinsen, O.. “Hydrodynamics of High-Speed Marine Vehicles.” (2006).

Savitsky, D., Morabito, M. "Surface Wave Contours Associated With the Forebody Wake of Stepped Planing Hulls." Marine Technology. 47. 1-16, (2010).

Gawn, R.W.L., Burrill, L.C. "Effect of cavitation on the performance of a series of 16 in. model propellers." Trans. RINA, 1957.

Newton, R.N., Rader, H.P. "Performance data of propellers for high speed craft." Trans. RINA, 103, 1961.

TEACHERS AND EXAM BOARD

LESSONS

LESSONS START

https://corsi.unige.it/en/corsi/11958/students-timetable

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

Oral exam. During the exam the student will have to present his assignment on the application of the Savitsky method on a test case chosen by the candidate. Furthermore the student will have to answer to one/two questions aboout topics addressed during the course (the number of question will depend on the detail of discussions).

During the discussion of the assignement the students capability will be assessed focusing on:

Capability to interpret obtained results and derive useful indication for the hydrodynamic design of a planing hull. As an example the student will need to comment on the effects of some geometrical parameters of the hull on its performances, identifying values and trends improving the efficiency of the unit (note: this does not mean using a proper optimization procedure whose theoretical basis are not addressed within the course).

Theoretical questions will allow assessing the capability of the student to remember and understand theories and methods addressed during the course.

The grade will be defined based on the overall assessment of the assignment and answers of the candidate.

ASSESSMENT METHODS

During the exam., the achievement of the aims of the course will be assessed with a special focus on:

Capability to remember and describe the base concept of the addressed topics (e.g. physical principles, simplifying assumptions, relations among quantities of interest etc.). It is not mandatory to remember precisely all the equations and formulations considered in the course while it will be instead assessed the capability to remember and describe the existance of formulations, the methods and assumptions used to derive them, their validity and the involved quantities. 

Capability to reason on high speed crafts hydrodynamics bases on theories and methods studied within the course.

Acità to describe autonomously the use of methods addressed within the course with a special focus on their applicability domain, computational procedures, and analysis of results.

Ability to use proper technical language

FURTHER INFORMATION

Ask the professor for other information not included 
in the teaching schedule