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In the last decade the popularity of hydrofoil-assisted monohulled yachts has increased, especially for high performance racing crafts, as the ones used in the Vendée Globe. In the academic environment some research has been done to follow the industry evolution to better understand the behaviour of such vessels, yielding to the need of developing a tool able to predict the performance of such boats. For this reason, the present document aims to propose a simplified model that forecasts the velocity of hydrofoil-assisted monohulled yachts through the development of velocity prediction program (VPP).
Due to the complexity of describing the behaviour of a complete sailing yacht, the developed tool uses empirical and analytical equations only, being a useful solution for a preliminary design stage. The aerodynamic model is based in the Offshore Racing Congress (ORC) documentation, the hydrodynamic model uses the Delft Systematic Yacht Hull Series (DSYHS) method, and the foil model is based in the Glauert’s biplane theory, corrected and adapted for hydrofoil with towing tank tests. The combination of the three models allowed the development of a VPP that balances forces and moments in three degrees of freedom: surge, sway and roll.
The VPP includes three different hydro foils designs: Dali Moustache, developed for the IMOCA 60 class by VPLP and used in the 2016-17 Vendée Globe regatta; Chistera, also developed by VPLP but now for the new Beneteau Figaro 3; Dynamic Stability System, patented by Hugh Burkewood Welbourn and largely used in several different vessels for racing and cruising.
Finally, the present thesis: compares the performance of different foils, pointing its advantages and drawbacks; discuss possible optimizations for the foils design and the precautions that should be taken; presents the limitations of the used models, which yields to the VPP limitations and suggests future works that should be done to better predict the performance of such yachts.

velocity prediction program, sailing yacht, hydrofoil, fluid dynamics, preliminary design. --- Ingénierie, informatique & technologie > Ingénierie civile

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Increasingly tight schedules in ship building projects as well as the opportunity of reliable RANS CFD codes including fast and flexible meshing methods lead to the application of numerical propulsion tests as standard procedures in the propeller design process. Due to the benefits of numerical self-propulsion simulations, the investigation of the ship propulsion characteristics and the analysis of fluid flow around the hull, propeller and rudder can be easily done with the relevant computational time consumptions. In this thesis, the propulsion efficiency of the ship is mainly investigated when the axial position of the propeller behind hull is varied. Furthermore, the flow field around the ship hull and operating propeller is presented and analyzed according to the changes of propeller position behind hull. The pressure quantities exerted on the hull at certain points are determined when the positions of propeller operating behind the ship hull are relocated. These numerical investigations are made for the self-propulsion simulations with and without rudder condition to observe the influence of rudder. With a view to fulfill the objectives of this thesis, the numerical propulsion simulations of the ship for different propeller positions with&without rudder conditions and reverse open water simulation of that propeller are performed by using commercial code RANSE solver, ANSYS CFX. All of the simulations are carried out in model scale of research vessel’s hull, its corresponding propeller and rudder. With the results of these simulations, the powering prediction results and propulsion characteristics data in full-scale operating conditions are extrapolated from model scale results by using the ITTC 1978 service performance prediction procedure. The results of propeller hydrodynamic performance and self-propulsion characteristics are analyzed to compare and investigate the propulsion efficiency between the different positions of propeller operating behind the hull with&without rudder conditions. Finally, the distribution of pressure and velocity contour are executed to study the flow effects on the hull-propeller-rudder interaction

Ingénierie, informatique & technologie > Ingénierie civile

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General Seakeeping qualities of the projected 53-meter and 46-meter motor yachts have been determined by means of theoretical calculations. With the help of a Two-dimensional source distribution program and a linear strip theory method various ship motions and acceleration as well as different extreme effects like deck wetness and bottom slamming were derived for the vessel running in irregular short-crested seaways. Thereby the full ranges of relative course angels and ship speed up to 16 knots have been taken into consideration. 
In this study two operational areas (Mediterranean and Aegean Sea) and three sea ways conditions (sea State 3, 4 and 5) were investigated which feature significant wave height in the range of 0.88 m and 3.25 m. 
The outcome of the theoretical study was checked against various performance criteria. The compliance of the projected motor yacht with limiting criteria is illustrated in the form of polar diagrams. Besides this, the seakeeping characteristics of the vessel (ship motion and extreme seakeeping effects) are represented in the form of Cartesian diagrams for all combination of seaway condition, relative course angle and ship speed. 
In sea State 3 conditions the projected vessels can run without restriction in both areas of operation. In contrast, some performance criteria are exceeded in sea State 4 while the operations of the yachts are restricted in sea State 5 by at least one performance criteria.

Ship Motion in Waves, Numerical Calculation, Extreme Effects, Motor yacht, Operational Criteria --- Ingénierie, informatique & technologie > Ingénierie civile

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The growing need for high efficient propulsion systems allied to the demand for accuratepowerpredictionswithlowercosts,justifytheusageofnumericalsimulations by companies in order to achieve strategic advantages over their competitors.
There are two approaches which can be used to find the self-propulsion point of a vessel, either experimentally or numerically, those are the load varying method, also known as British method and the constant loading method, commonly called as Continental method.
The British method requires at least two runs for each speed to determine the selfpropulsion point, a run with an under-loaded propeller and one with an over-loaded propeller, thereafter the propulsion point may be estimated.
Experimentally, the Continental method requires only one run to determine the propulsion point for each speed, this is possible due to the presence of a RPM corrector attached to the model which can adjust the propeller velocity during the run. Numerically, this feature may bring advantage over the British method by reducing computational time.
The main objective of this work is to propose and implement a suitable numerical model to estimate the self-propulsion parameters of the KVLCC2 using the Continental method, ANSYS CFD Package will be used for analyses.
ARPMcontrollerisfirstlyimplementedonasimplerbodyandaconvergencestudy is performed in order to determine an initial setup for the KVLCC2. Self-propulsion simulations are performed using the British and Continental methods, therefore comparison regarding accuracy and computational time between the two numerical methods are made. Finally, the report ends with conclusions and suggestions for further investigations.

CFD, self-propulsion, continental-method, british-method, numerical simulation --- Ingénierie, informatique & technologie > Ingénierie civile