Academic literature on the topic 'Hydrofoil boats'

A new-type hydrofoil catamaran has been designed and its resistance and seakeeping properties examined by experiments. This new catamaran is made of two sharp hulls like swords and two rectangular hydrofoils of high aspect ratio that connect them. Almost 90 percent of the weight is supported by the hydrofoils, and the total resistance coefficient is much smaller than that of conventional high-speed craft or similar designs at the design speed of 40 knots for a 200-ton boat. The transfer functions of motions are much smaller than those of planing boats and another hydrofoil catamaran of different configuration.

The interest in autonomous marine vessels has been continuously growing in the recent years. Most platforms of the autonomous surface watercraft involve traditional mono- or multi-hulls. Advanced marine vehicle concepts, such as hydrofoils, can provide high-speed and high seakeeping capabilities. In this study, a modeling effort is initiated for a small autonomous hydrofoil boat intended for intercepting operations. A 3-DOF model, including surge, sway and yaw, is applied for simulating maneuvering motions of the boat in the foilborne state. Forces generated by the propulsor, rudder and struts are accounted for in the simulations of the horizontal-plane boat dynamics. Two scenarios of a hydrofoil boat pursuing a moving target are investigated. In the pure pursuit, the interceptor always attempts to aim at the target and uses full thrust to quickly reach the target at a high speed. In the constant-bearing scenario, the interceptor approaches the target with diminishing speed trying to achieve a rendezvous. The presented models and results can help engineers to design more effective control methods for fast boats intended for intercepting operations.

Hydrofoils are a vital part of modern racing yachts such as the AC75, which was sailed in the 36th America’s Cup and should hence be optimised thoroughly. The literature shows that hydrofoil design and optimisation usually focuses on the lift and drag characteristics in isolation of the yacht ‘system’. Although these characteristics relate to hydrofoil performance, they do not directly translate to the performance of the yacht on the race course. In this paper we perform a parametric study of the main design variables of the hydrofoil that is based on a model of the entire yacht in the Velocity Prediction Program (VPP) FS-Equilibrium. The hydrofoil forces are modelled using an advanced lifting line method and empirical formulations for a bulb. This accurately captures the foil design influence on the boat´s performance. The VPP is coupled to a parametric model of the foil based on NURBS surfaces (Non-uniform rational B-Splines) which was used to systematically generate 72 different designs. The candidates were tested in three wind speeds for up and downwind performance. The best performing design has maximum span and anhedral angle, and minimum chord with some of the weight stored in a bulb. The study shows that the assessment of hydrofoils where the performance is measured in boat speed is an extremely valuable tool.

Amphibious aircraft designers face challenges to improve takeoffs and landings on both water and land, with water-takeoffs being relatively more complex for analyses. Reducing the water-takeoff distance via the use of hydrofoils was a subject of interest in the 1970s, but the computational power to assess their designs was limited. A preliminary computational design framework is developed to assess the performance and effectiveness of hydrofoils for amphibious aircraft applications, focusing on the water-takeoff performance. The design framework includes configuration selections and sizing methods for hydrofoils to fit within constraints from a flying-boat amphibious aircraft conceptual design for general aviation. The position, span, and incidence angle of the hydrofoil are optimized for minimum water-takeoff distance with consideration for the longitudinal stability of the aircraft. The analyses and optimizations are performed using water-takeoff simulations, which incorporate lift and drag forces with cavitation effects on the hydrofoil. Surrogate models are derived based on 2D computational fluid dynamics simulation results to approximate the force coefficients within the design space. The design procedure is evaluated in a case study involving a 10-seater amphibious aircraft, with results indicating that the addition of the hydrofoil achieves the purpose of reducing water-takeoff distance by reducing the hull resistance.

Hydrofoils are a current hot topic in the marine industry both in high performance sailing and in new passenger transport systems in conjunction with electric propulsion. In the sailing community, the largest impact is seen from the America’s cup, where boats are sailed at more than 50 knots (over 100 km/h) with 100% “flying” time. Hydrofoils are also becoming popular in the Olympics, as in the 2024 Olympic games 5 gold medals will be decided on foiling boats/boards. The reason for the increasing popularity of hydrofoils and foiling boats is the recent advances in composite materials, especially in their strength to stiffness ratio. In general, hydrofoils have a very small wetted surface area compared to the wetted surface area of the hull. Therefore, after “take-off” speed, the wetted surface area of the hull, and consequently the resistance of the boat, is reduced considerably. The larger the weight of the boat and crew and the higher the speeds, the greater the loads on the hydrofoils will be. The current research investigates the interaction effects between the fluid and structure of the ZP00682 NACRA 17 Z-foil. The study is carried out both experimentally, in SSPA’s cavitation tunnel, and numerically using a fully coupled viscous solver with a structural analysis tool. The experimental methodology has been used to validate the numerical tools, which in turn are used to reverse engineer the material properties and the internal stiffness of the NACRA 17 foil. The experimental flow speed has been chosen to represent realistic foiling speeds found in the NACRA 17 class, namely 5, 7, and 9 m/s. The forces and the deflection of the Z-foil are investigated, showing a maximum deflection corresponding to 24% of the immersed span. Finally, the effects of leeway and rake angles on the bending properties of the Z-foil are investigated to assess the influence of different angles in sailing strategies, showing that a differential rake set-up might be preferred in search for minimum drag.

The hydrofoil is a hydro-lifting surface that significantly contributes to marine transportation such as a boat, ship, and submarine for its movement and maneuverability. The existing hydrofoils are in fixed-shaped National Advisory Committee for Aeronautics (NACA) profiles, depending merely on the variation of Angle of Attack (AOA) such as rudder, hydroplane, and propeller blade. This research is concerned with the deformable hydrofoil that aims at modifying its NACA profile rather than its AOA. However, there is still a lack of knowledge about designing an appropriate deformable hydrofoil. Therefore, a numerical investigation of hydrodynamic characteristics for selected hydrofoils was conducted. After undergoing the 2D numerical analysis (potential flow method) at specific conditions, several NACA profiles were chosen based on the performance of NACA profiles. NACA 0017 was selected as the initial shape for this research before it deformed to the optimized NACA profiles, NACA 6417, 8417, and 9517. The 3D CFD simulations using the finite volume method to obtain hydrodynamic characteristics at 0 deg AOA with a constant flow rate. The mesh sensitivity and convergence study are carried out to get consistent, validated, and reliable results. The final CFD modeled for propeller VP 1304 for open water test numerically. The results found that the performance of symmetry hydrofoil NACA 0017 at maximum AOA is not the highest compared to the other deformed NACA profiles at 0 deg AOA. The numerical open water test showed that the error obtained on K.T., K.Q., and efficiency is less than 8% compared to the experimental results. It shows that the results were in good agreement, and the numerical CFD setting can be used for different deformed profiles in the future.

An Eppler 817 (E817) hydrofoil was studied experimentally using two dimensions two components Particles Image Velocimetry (PIV) measurements. Both statistical and time-resolved series were used to study the effect of Reynolds number and angle of attack on the flow topologies and dynamics. Vortex shedding modes were observed over a range of low chord-based Reynolds numbers 400 ≤ Rec ≤ 20000 and four angles of attack ( α = 2◦, 6◦, 12◦ and 30◦). Those Reynolds numbers are scarce documented on such hydrofoil as they are far from usual operating conditions. However, those low Reynolds numbers allowed us to observe Reynolds number based transitions of the vortex shedding modes at a given angle of attack. The data were acquired on both an extruded 2D hydrofoil and a 3D "T-shaped" hydrofoil, composed of a vertical shaft (e.g. rudder on a boat) holding the horizontal lifting surface. The latter was used to investigate the influence of both the 3D shape and surface proximity on the hydrofoil’s behaviour through three different depths, ranging from 3.5 to 0.875 chords. Additional measurements from a 6-axis loads sensor were used to characterize the loss of performance due to the free-surface proximity.

Recent demands for higher speed ocean vehicles and, at the same time, for more efficient propulsion, have made the appearance of cavitation inevitable. Thus, contemporary hydrofoil or propeller blade designs must take advantage of controlled cavitation in order to increase the efficiency of propulsion. An International Consortium on Cavitation Performance of High-Speed Propulsors has been put together by the author. The ultimate objective of this effort is to develop a new generation of reliable and user-friendly computational tools for the analysis and systematic design of efficient cavitating hydrofoils or propulsors. Fifteen participants have joined this consortium thus far. They include research centers, propeller manufacturers, shipyards, and high-speed boat industries from the U.S., Europe, and Asia. An overview of the research plan and the approach for some of the research tasks are presented.

Thesis (PhD)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: This work is concerned with the hydrodynamic design of hydrofoil-assisted catamarans. Focus is placed on the development of new and suitable design methods and application of these to identify the most important geometric parameters of catamaran hulls and hydrofoil configurations that influence efficiency and performance. These goals are pursued by firstly gaining a thorough understanding of the governing hydrodynamic principles involved in the design process. This knowledge is then applied to develop new and improved experimental techniques and theoretical methods needed for design. Both are improved to the extent where they can be applied as design tools covering the important semi-displacement and semi-planing speeds, which are the focus of this study. The operational speed range of hydrofoil-assisted catamarans is shown to consist of three distinct hydrodynamic phases (displacement, transition and planing) and that different hydrodynamic principles govern vessel performance in each phase. The hydrodynamics are found to differ substantially from that of conventional high-speed craft, primarily due to the interaction between the hull and the hydrofoils, which is found to vary with speed and results in the need for more complex experimental procedures to be followed if accurate predictions of resistance are to be made. Experimental predictions based on scaled model tests of relatively small hydrofoilassisted catamaran models are found to be less accurate than that achievable for conventional ships because of the inability to correct for all scaling errors encountered during model testing. With larger models scaling errors are encountered to a lesser degree. The most important scale effect is found to be due to the lower Reynolds number of the flow over the scaled foils. The lower Reynolds number results in higher drag and lower lift coefficients for hydrofoils compared with those achieved at full scale. This effect can only be partially corrected for in the scaling procedure using the available theoretical scaling methods. Presently available theoretical methods commonly used for the design of conventional ships were found to be ill adapted for modeling the complex hydrodynamics of hydrofoil-assisted catamarans and required further development. Vortex lattice theory was chosen to model the flow around hydrofoil-assisted catamarans as vortex theory models the flow around lifting surfaces in the most natural way. The commercial code AUTOWING is further developed and generalized to be able to model the complex hull-hydrofoil interactions that change with speed. The method is shown to make good predictions of all hydrodynamic quantities with accuracies at least as good as that achievable through model testing and therefore fulfills the requirements for a suitable theoretical design tool. The developed theoretical and experimental design tools are used to investigate the design of hydrofoils for hydrofoil-assisted catamarans. It is found that the main parameter needing consideration in the hydrofoil design is selection of a suitable hydrofoil lift fraction. A foil lift fraction in the order of 20-30% of the displacement weight is needed if resistance improvements using hydrofoil assistance are to be obtained over the hull without foils. It is often more favorable to use higher foil lift fractions (50%+) as the resistance improvements are better, although careful attention should then be given to directional and pitch-heave instabilities. The Hysuwac hydrofoil system patented by the University of Stellenbosch is found to be hydrodynamically optimal for most hullforms. The hullform and in particular the curvature of the aft buttock lines of the hull are found to have an important influence on the achievable resistance improvements and behaviour of the hydrofoil-assisted hull at speed. Hull curvature is detrimental to hydrodynamic performance as the suction pressures resulting from the flow over the curved hull counter the hydrofoil lift. The hullform best suited to hydrofoil assistance is found to be one with relatively straight lines and hard chine deep- V sections. The main conclusion drawn from this study is that hydrofoil-assistance is indeed suitable for improving the performance and efficiency of catamarans. The design and optimization of such vessels nevertheless requires careful consideration of the various resistance components and hull-foil interactions and in particular, how these change with speed. The evaluation of resistance for design purposes requires some discipline between theoretical analysis and experimental measurements as the complexity of the hydrodynamics reduce the accuracies of both. Consideration of these factors allows hulls and hydrofoils to be designed that are efficient and also free of dynamic instabilities.
AFRIKAANSE OPSOMMING: Hierdie studie is gerig op die hidrodinamiese ontwerp van hidrovleuel-gesteunde katamarans. Daar word gefokus op die ontwikkeling van nuwe en geskikte ontwerpmetodes, asook die toepassing van hierdie metodes om die belangrikste geometriese parameters van katamaranrompe en hidrovleuel-konfigurasies wat 'n invloed op doeltreffendheid en werkverrigting het, te identifiseer. As aanloop tot die studie is 'n deeglike begrip van die onderliggende hidrodinamiese beginsels bekom. Hierdie kennis is toegepas om nuwe en verbeterde eksperimentele en teoretiese tegnieke te ontwikkel wat nodig is vir die ontwerp van hidrovleuel-gesteunde katamarans in die belangrike deels-verplasing en deels-planering spoedbereike. Daar word getoon dat die bedryfspoedbereik van 'n hidrovleuel-gesteunde katamaran uit drie onderskeibare hidrodinamiese fases bestaan, naamlik verplasing, oorgang en planering, en dat verskillende hidrodinamiese beginsels die vaartuig se werkverrigting in elke fase bepaal. Daar is ook gevind dat die hidrodinamika wesentlik verskil van dié van konvensionele hoëspoed-vaartuie, hoofsaaklik as gevolg van die interaksie tussen die romp en die hidrovleuels wat wissel na gelang van die spoed. Hierdie interaksies moet in ag geneem word gedurende die ontwerpproses en beide eksperimentele en teoretiese metodes is nuttig om die omvang daarvan te bepaal. Daar is gevind dat die eksperimentele voorspellings gebaseer op toetse met relatief klein skaalmodelle van hidrovleuelgesteunde katamarans minder akkuraat is as dié wat bereik kan word met konvensionele skepe. Dit is omdat al die skaalfoute wat tydens die toetsing met die model ontstaan, nie gekorrigeer kan word nie. Die belangrikste skaaleffek is as gevolg van die laer Reynoldsgetal van die vloei oor die afgeskaalde vleuels. Groter modele Die laer Reynoldsgetal lei tot hoër sleur- en hefkoëffisiënte in vergelyking met dié vir die volskaal-hidrovleuels. Wanneer die beskikbare teoretiese metodes gebruik word, kan daar slegs gedeeltelik vir hierdie effek in die skaalprosedure gekorrigeer word. Daar is ook vasgestel dat die skaaleffekte op die Reynoldsgetal verminder word wanneer die hidrovleuels baie nabyaan die vrye oppervlakte is. Dit lei daartoe dat eksperimentele voorspellings van werkverrigting meer akkuraat is vir die ontwerpe waar die hidrovleuels nie so diep onder die water is nie. Daar is gevind dat die teoretiese metodes wat tans beskikbaar is en algemeen vir die ontwerp van konvensionele skepe gebruik word nie die komplekse hidrodinamika van hidrovleuel-gesteunde katamarans kan modelleer nie. Die werwelroosterteorie is gekies om die vloei om hidrovleuel-gesteunde katamarans te modelleer aangesien dié teorie die vloei om hefvlakke op die natuurlikste manier weergee. Die kommersiële kode AUTOWING is verder ontwikkel en veralgemeen om ook die komplekse spoed-afhanklike interaksies van die romp en hidrovleuel te kan modelleer. Hierdie metode lewer goeie voorspellings van al die hidrodinamiese maatstawwe met akkuraathede wat ten minste so goed is soos di wat met modeltoetsing bereik word en voldoen daarom aan die vereistes vir 'n geskikte teoretiese ontwerpmetode. Die teoretiese en eksperimentele ontwerpmetode wat ontwikkel is, word gebruik om die ontwerp van hidrovleuels vir hidrovleuel-gesteunde katamarans te ondersoek. Daar is gevind dat die belangrikste parameter wat in die hidrovleuel-ontwerp in ag geneem moet word, die keuse van 'n geskikte hidrovleuelhefverhouding is. Om in rompe met hidrovleuelsteun verbeterings in die weerstand te kry in vergelyking met rompe sonder vleuels, is 'n vleuel-hef-verhouding van 20-30 persent van die verplasingsgewig nodig. Dit is dikwels beter om hoër vleuel-hef-verhoudings (van 50 persent of meer) te gebruik omdat die verbetering in weerstand dan groter is. Daar moet dan egter gewaak word teen rigtings- en hei-hef-onstabiliteite. Daar is gevind dat die Hysuwachidrovleuel- stelsel wat deur die Universiteit van Stellenbosch gepatenteer is, hidrodinamies optimaal is vir die meeste rompvorms. Daar is gevind dat die vorm van die romp en veral die kromming van die lyne gevorm deur vertikale snitte deur die romp (Engels: "aft buttock lines") van die romp 'n belangrike invloed het op die bereikbare weerstandsverbeterings en die gedrag van die hidrovleuel-gesteunde romp wat op spoed is. Die kromming van die romp is nadelig vir die hidrodinamiese werksverrigting aangesien die suigdruk as gevolg van die vloei oor die gekromde romp die hefkrag van die hidrovleuels teenwerk. Die rompvorm wat die geskikste is vir hidrovleuel-ondersteuning is 'n romp met relatiewe reguit lyne en skerp hoekige diep- V seksies. Die belangrikste gevolgtrekking waartoe tydens die studie gekom is, is dat hidrovleuelondersteuning wel geskik is vir die verbetering van die werkverrigting en die doeltreffendheid van katamarans. Die ontwerp en optimering van sodanige vaartuie verg nogtans die noukeurige oorweging van die verskeie weerstandskomponente en rompvleuel- interaksies en veral hoe hierdie interaksies verander met spoed. Die evaluering van die weerstand vir die doeleindes van ontwerp verg dissipline tussen die teoretiese analise en die eksperimentele metings aangesien die kompleksiteit van die hidrodinamika die akkuraatheid van die algemeen-gebruikte teoretiese en eksperimentele metodes vir die hidrodinamiese ontwerp verminder. As hierdie faktore in ag geneem word, kan rompe en hidrovleuels ontwerp word wat doeltreffend is en ook vry is van dinamiese onstabiliteite.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008.
This study investigates practical passive methods to improve the seakeeping of a Hydrofoil Supported Catamaran (Hysucat). The Hysucat is a hybrid vessel combining hydrofoil efficiency with the stability of catamarans. The seakeeping of the Hysucat was initially investigated experimentally to determine what seakeeping improvements are inherent to the Hysucat design. The results showed that the seakeeping is improved by 5-30%. A passive suspension system for the main hydrofoil of the Hysucat was designed and tested. A concept development strategy was followed for the design of the suspension system as such a system had never been investigated previously. Detailed specifications for the design were developed and concepts that could satisfy the customer and engineering requirements were generated. Numerical simulation models for the Hysucat and the final concepts were derived assuming a simplified 2nd order system to describe the seakeeping dynamics of the demi-hulls. Unknown parameters were determined using parameter estimation techniques. Representative parameter values were calculated from multiple towing tank experiments. Theory describing the motion of a hydrofoil in an orbital velocity wave field was combined with the hull model to simulate the Hysucat as well as the suspension system concepts. The models indicated that the concept where the main hydrofoil was attached to a spring loaded arm, that was free to pivot in response to orbital waves, was the most feasible in damping out vertical transmitted accelerations. Experimental tests indicated that little improvement was achieved with the suspension system at low frequencies. At resonance the suspension system was effective in decreasing the heave of the vessel by up to 27%. The pitch and acceleration response results showed improvements at the higher encounter frequencies of up to 50%. The calm water resistance of the vessel increased by 10% over the Hysucat with rigidly attached hydrofoils; however was still 24% less than the hull without foils.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2006.
This thesis investigates practical methods of modelling and control of the vertical motions of a hydrofoil assisted catamaran, the HYSUCAT. The aim of the control application is to reduce the motions, and consequently the motion sickness of the passengers. First, a potential flowcommercial program, POWERSEA,was used to model the system. This uses 2-D strip methods to model the planing hull-form of the vessel, and the Peter du Cane hydrofoil theory for modelling of the foils. These simulations are compared to experimental towing tank results, with fair agreement at lower speeds, but limited applicability at high speeds. Thus for the control design the agreement was insufficient. As an alternative, a simple coupled 2 degree-of-freedom spring - mass - damper model is proposed, for which the equations of motion are derived. This has 9 unknown parameters; three of these aremeasured directly, two are modelled, and the remaining four were identified using an experimental parameter estimation technique. Representative parameter values were calculated frommultiple experiments for application in the control design. The design of a control system was based on the above model. First, an output-weighted Linear Quadratic Regulator (LQR) was designed to obtain the full state feedback gains. A non-linear ’bang-bang’ control design was then implemented to try and speed up the response of the system. These control strategies, as well as no control, were applied in the towing tank in regular waves, with good results at low and medium frequencies. At the design point, 32% and 65% reductions in rms motions were achieved for pitch and heave, respectively. At high frequencies, though, not much improvement was achieved due to the bandwidth limitation of the control system. The LQR results were better overall (reduced motions) across the frequency range than the bang-bang controller, as well as having a lower added resistance in waves. The control design of the output-weighted LQR was then revised to be based on alternative outputs, as a possible improvement. However, a further two controller designs did not yield any noticeable improvement and were not developed further.

Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (page 80).
This thesis presents the preliminary design and assessment of Wavecutter, an innovative super high speed, hybrid hydrofoil/SWATH crew boat. The intended mission of the vessel is the very-fast transportation of crew and cargo, to and from offshore installations. The design builds on Brizzolara's unmanned high speed hybrid SWATH/hydrofoil vessel concept (Brizzolara, 2010), maintaining the dual operating mode: foilborne to reach top speed of 85 knots in moderate sea states and a displacement SWATH to sail in the higher sea states. This vessel is expanding the family of unmanned hybrid SWATH vessels of Brizzolara and Chryssostomidis to include manned vessels (Brizzolara & Chryssostomidis, 2013). The special hydrofoil profile recently optimized and verified by model tests in free-surface cavitation tunnel, has been adopted, to ensure high lift to drag ratios and avoid typical instability phenomena of conventional super-cavitating hydrofoils (Brizzolara, 2013). The surface piercing configuration of the hydrofoils was adopted in order to make the vessel inherently stable, without the use of control mechanisms. The general design phase was focused on the integration of the manned module, internal arrangements, weight estimation, speed profile determination and engine selection. The hydrofoil design phase limits on resizing the four surface-piercing super-cavitating hydrofoils to keep the vessel even keel at maximum speed. To achieve this, the front foils need to have a larger size than the aft ones, due to the trim moment produced by the turbo-jet thrust force. The feasibility assessment phase in foil borne mode confirmed the static stability of the vessel and good seaworthiness in waves. It is recommended that future work be conducted with CFD simulations in unsteady conditions, to obtain a more accurate understanding of the vessel's dynamic behavior.
by Vasileios Georgiadis.
Nav. E.
S.M.

This Master Thesis illustrates the physics behind the mathematical model of a foiling dinghy to be used in a model-based autopilot architecture, and the multiple frames of references needed for an exhaustive force description. Using the modeled foiling boat, we performed the non-trivial task of finding meaningful trim setpoints, which were then used throughout the simulations. We applied Optimal Control theories to achieve stability and control of a foiling dinghy with a movable crew at different trim settings and various environmental parameters, such as wind speed and sea state, both stationary and time-varying. We developed a prototype of a gain scheduler for the closed-loop to perform tack and jibes maneuvers in multiple environments, and compared the stability and parameters sensitivity of different closed feedback loop architectures, both in a straight line and maneuvering performance. The maneuvering performances were established with extensive ad-hoc simulations to properly characterize the behavior of the architecture, while the straight-line response and parameter variation sensitivity was determined through Monte Carlo simulations. At the end of this paperwork, the two best performing closed-loop architectures proposed were compared to determine which one would be the more promising for a practical application.

碩士
國立臺灣大學
工程科學與海洋工程學系
91
The main purpose of this study is to design a solar/electric hydrofoil boat. The design requirements are based on the rules of Solar Splash boat regatta. First, we use diverse CAD software to design subsystems of the boat such as hull-form, electric propulsion system, assisting hydrofoil system for producing lift and outfitting system. CFD method is then used for analyzing resistance and propulsion as well as lifting force performances. The target is to establish a complete product data model of a solar/electric hydrofoil boat. In this study we design the hull-form and use solar/electric in propulsion system. We also design hydrofoil which can reduce the frictional drag force of the boat. Then we analyze lift force, structure, deformation about the hydrofoil. In the end we design the control machine. At the same time we build up the 3D model for every component. The construction of the whole geometrical model is based on product data management (PDM) rule so that the data can be used directly for building the boat.

Hydrofoils allow for boats to reach greater speeds by lifting the hulls of the boat out of the water. This reduces the drag due to the hulls pushing through the water. Implementing this technology on energy ships, sailboats or kiteboats that generate renewable energy using wind power, can increase the efficiency of such energy generating systems. A hydrofoil design was developed and manufactured for a Hobie 17 sailboat to allow for preliminary testing of the energy ship concept. A V-shape hydrofoil design was used to provide hands-free foiling of the sailboat. The advantages and disadvantages of this configuration are explored. An attachment mechanism is also described that allows for the user to preset the angle of attack of the dihedral hydrofoils, and an analysis of the adjustment angle’s impact on the hydrofoils′ angle of attack is quantified. Since the V-shape hydrofoil design pierces the water’s surface, ventilation becomes an issue due to air being sucked down the low-pressure lifting surface of the hydrofoils. To reduce ventilation, fences were added along the top surface of the hydrofoils. The hydrofoil design was tested and proven to be a feasible configuration for wind powered boats.

Hydrodynamic arrangements of most autonomous surface marine vessels belong to conventional displacement-type monohulls or catamarans. Applications of advanced hydrodynamic concepts, such as considered here hydrofoils, can help unmanned marine craft operate efficiently at higher speeds and have better seakeeping. However, dynamics of such boats are rather complex. In this work, a 6-DOF dynamics model with engineering correlations for hydrodynamic forces is applied to simulate motions of an autonomous hydrofoil craft. Collision avoidance maneuvers based on introduction of a dynamic waypoint outside unsafe zone around a moving obstacle have been modeled. The description of planning decisions, implementation of controls, simulated boat trajectories, and time histories of kinematic and controlled variables are presented and discussed. The developed model can be used for design of unmanned hydrofoil craft and control systems of fast autonomous boats.

The advances in sailing boat races have been greatly proven in the recent America’s Cup competition. Sailing boats have reached speeds above 40 knots with a simple concept: the wetted surface of the hull is minimized and the required displacement is obtained through a lifting force produced by submerged hydrofoils working at very high speeds. This is a well-known concept in naval architecture that has been exploited since the beginning of the 20th Century. Hydrofoils used in sailing boat races are yet not designed for cavitating flow, but major changes in the design will be needed in case speed increases above 50 knots. When highspeed crafts (including fast sailing boats) operate significantly above the planing threshold speed, the convenience of completely or partially supporting their weight by lifting hydrofoils is evident (Du Cane (1964)). A very low pressure field induced by high in flow speed triggers water vaporization at ambient temperature: cavitation cannot be avoided and foil shape has to be designed with the goal of maintaining a stable flow regime eventually com-promising the lift. When craft speed arise above 50 knots, the de-sign philosophy for the basic section of the lifting hydrofoil has to radically change and turn to super-cavitating hydrofoils (Auslaender [1962]) being the final goal addressed towards the delay and stabilization of the cavity shape over the hydrofoil surface. In super-cavitating regimes the suction surface of the hydrofoil is fully enveloped in the cavity which (typically) detaches at the leading edge of the foil and closes in the wake well aft the trailing edge. The pressure side of the hydrofoil is the only responsible for lift generation thus the main design target is represented by the shape of the foil surface. Several simplified theories assuming steady state potential flow (mentioned later in this introduction) were developed in the past to deal with this essential design problem.

Cedarville University competes annually in the Solar Splash competition, which involves teams of undergraduate students designing and racing boats powered by batteries and solar energy. In past years team members have used several analysis tools to estimate the drag and lift generated by both the hull of the boat or prospective hydrofoil systems. In 2014 Putnam, Dickert, and Wagner used ANSYS’s computational fluid dynamics (CFD)software, Fluent, to estimate the lift and drag of hydrofoils in a single-phase water flow. Their design used the standard “T-junction” design seen in Figure 1. In 2014 (the next team iteration) Howland used the same software to analyze the drag on an existing hull design while using a 2-phase water-and-air flow.

Abstract Hydrofoils have become a popular design addition to different kinds of waterborne vessels, particularly yachts and race boats. A prime example of this is the Americas Cup yacht regatta, where hydrofoils are now a mainstay of boat architecture. Hydrofoils permit vessels to lift their hulls above the water surface through the generation of lift. When in this “foiling” regime, the drag forces on the hull are drastically lower, permitting greater sailing speed. Predicting hydrodynamic forces produced from hydrofoils on race yachts remains challenging, due to a wide operating regime and complex hydrodynamical phenomena. The purpose of this study was to investigate methods of decomposing the total drag force of a hydrofoil from computational fluid dynamics (CFD) simulations into its physical components. A rectangular NACA4412 was simulated fully submerged at a depth of one chord. Viscous flow was simulated with the k-ω SST turbulence model in steady state; and the volume-of-fluid (VOF) model was used to capture free surface effects. Chord Froude numbers of 0.5, 1, 2 and 4 were investigated, corresponding to Reynolds numbers of 2.57 × 105, 5.15 × 105, 1.03 × 106 and 2.06 × 106. Force decomposition was performed using wave pattern analysis, Trefftz plane analysis and viscous wake surveys. These yielded the wave-pattern, induced, and viscous drag components respectively. Wave drag was seen to decrease with Froude number, while the induced drag increased. The sum of viscous and wave drag closely approximated the total drag computed using surface integration, supporting the Froude decomposition of drag force. Induced drag was seen to interact with the other drag components and became the dominant component at Froude numbers above unity.

In 2007 Canada entered its first challenge for the International C-Class Catamaran Championship and was victorious in capturing the trophy with five straight wins by Alpha CAN 6 over the venerable Cogito from the USA. Two boats were designed for this challenge - the first was Alpha, a wingsail catamaran, which incorporated some new thinking on sail configuration and hull shape. This made it a successful evolutionary, but not revolutionary, step from the current state-of-the-art boats. Compared to Cogito, the main rival, she had a taller, narrower and thinner wing, lighter construction and more circular hull cross section. The second was Rocker, the bold hydrofoil catamaran, using hulls from the same mold as Alpha and an identical wingsail as the driving force. The daggerboard hydrofoils automatically controlled the ride height with trim tabs, while the control of the rudder elevators was left to the helmsman. Although she flew well, was very controllable, and was spectacular to watch, Rocker could not match the 20 knot plus speed of Alpha.

A new concept of hydrokinetic turbine using oscillating hydrofoils to extract energy from water currents (tidal or gravitational) is presented, tested and analyzed in the present investigation. Due to its rectangular extraction plane, this technology is particularly well suited for river beds and shallow waters near the coasts. The present turbine is a 2 kW prototype, composed of two rectangular oscillating hydrofoils of aspect ratio 7 in a tandem spatial configuration. The pitching motion of each hydrofoil is coupled to their cyclic heaving motion through four-link mechanisms which effectively yield a one-degree-of-freedom system driving a speed-controlled electric generator. The turbine has been mounted on a custom-made pontoon boat and dragged on a lake at different velocities. Instantaneous extracted power has been measured and cycle-averaged for several water flow velocities and hydrofoil oscillation frequencies. Results are demonstrated to be self-consistent and validate our extensive 2D flow simulation database. The present data show optimal performances of the oscillating hydrofoils concept at a reduced frequency of about 0.12, at which condition the measured power extraction efficiency reaches 40% once the overall losses in the mechanical system are taken into account. Further measurements of power extraction with a single oscillating hydrofoil have also been performed by taking out the downstream hydrofoil of the tandem pair. Those measurements favorably compare, quantitatively, with available 3D CFD predictions. The 40% hydrodynamic efficiency of this first prototype exceeds expectation and reaches levels comparable to the best performances achievable with modern rotor-blades turbines. It thus demonstrates the promising potential of the oscillating hydrofoils technology to efficiently extract power from an incoming water flow.

The purpose of this paper is to demonstrate the extent to which the Athena Vortex Lattice program (AVL) is useful in the design of a hydrofoil system for a solar boat. Cedarville University has won the Solar Splash Collegiate World Championship of Solar Boating 8 times in the past 12 years, and was the top university in the Top Class of the 2012 DONG Energy Solar Challenge in the Netherlands. The three main events of the Solar Splash Competition are the high-speed Slalom and Sprint events, and the longer Endurance event. In the past Cedarville has attempted to design and use hydrofoils for the Endurance event without success. Computational Fluid Dynamics (CFD) analysis for a hydrofoil system was conducted by Neola Putnam (2013 team member) using ANSYS’s CFD software, Fluent. Putnam worked with single phase flow modeling 3D hydrofoils. Fluent analysis can be a long and complicated process requiring hours of meshing followed by hours of CPU time for analysis. AVL, as an alternative, is a less complicated program allowing for simple generation of a geometry file. This program also takes a comparatively short time to analyze the imported geometry file. Thus, if AVL reliably predicts lift and drag, it could be used as a preliminary design tool to quickly assess various design options. AVL is a program which models lifting surfaces as vortex lattice sheets to determine the flight characteristics of the surface. The program is written in Fortran and is an inviscid solver. The AVL3.30 User Primer is a reference guide on how to use the program and was used extensively by the authors of this paper when learning to use AVL. Cedarville University also partnered with the company Sea Land Aire Technologies Inc.in Jackson Michigan for aid in using AVL as a design tool. The tool was recommended to Cedarville University by Sea Land Aire as a product which might be of interest to our team in the design of a hydrofoil system. AVL is potentially beneficial to the Cedarville University Solar Boat team in the preliminary design phase of a hydrofoil system. The content of this paper demonstrates the correlation between results from AVL and Fluent analysis for a 2D NACA 4412 foil. Secondly, the paper demonstrates comparable results from AVL for 3Danalysiswith published experimental results. The following sections discuss the use of AVL as a preliminary design tool, and the overall recommendation of the authors as to further use of AVL by Cedarville University in the design of a hydrofoil system.

Hydrofoils are used in the marine industry to produce enough lift to raise the boat and crew out of the water, therefore reducing resistance on the hull and enabling increased speeds. The interaction between the hydrofoil and water puts severe stress and strain on the hydrofoil. Fluid-structure interaction (FSI) is a multi-physics coupling of both fluid dynamics and structural mechanics into one simulation. When a fluid flow interacts with a structure, stresses and strains are applied within the structure which can lead to a deformation, which can change the flow field, giving a revised pressure loading. This change in pressure loading can lead to either an increase or decrease in lift, which is dependant on the location of the elastic axis of the hydrofoil. If the pressure loading is increased and left unchecked, the deformation could lead to failure of the structure. A symmetrical hydrofoil is studied and good agreement to within 1% variation in pressure is found between the simulated fluid and experimental results found in literature. Good agreement is essential for FSI as any differences can be amplified in subsequent iterations of the FSI. The FSI effects of lift are reported with varying material properties for the NACA0012 hydrofoil. The lift was found to be highly dependent on structural rigidity. The FSI effects are reported for a particular case with a tip deflection of 45cm which is 23% of span. This results in an increase of lift by a factor of 19%, although much larger deformations are possible. In addition, the effects of an FSI on the more complex geometry of the daggerboard on the AC45F foiling boat used in America’s Cup are presented. Here, due to FSI effects, the tip deflection of 32cm changes the coefficient of lift by a factor of 10%. All FSI simulations are found to be stable and give an indication of material strengths needed. However, in all analyses we simplify the structural simulation by treating the structure as a solid volume with isotropic material properties. Future work including the use of anisotropic material properties are highlighted.