| 1. |
- Banhegyi, Eliza, et al.
(författare)
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Prediction of Wind Fields using Weather Pattern Recognition : Analysis of Sailing Strategy and Real Weather Data in Tokyo 2020 Olympics
- 2022
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Ingår i: Journal of Sailing Technology. - : The Society of Naval Architects and Marine Engineers. - 2475-370X. ; 7:01, s. 186-202
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Tidskriftsartikel (refereegranskat)abstract
- The Tokyo 2020 Olympic Sailing Competitions were held in Enoshima Bay between the 25th of July and the 4th of August 2021. The climatological and the strategical analysis of the race area for the Swedish Sailing Team was developed in the three years prior to the Olympics (Masino et al., 2021). The result of the three years’ research was a tool named ”Call Book” that provides strategical rules for sailors and coaches both in terms of expected ranges of wind speed and direction and also in terms of trends with explanations for each identified weather pattern. The support team was working not only on the forecast but also on the specific analysis of the weather data in the race areas as measured on the water by the Olympics organizing authorities and monitored through the SAP Analytics website (SAP Sailing Analytics, 2021). Two race areas are herein taken into consideration, namely Enoshima and Zushi, where the Swedish Team athletes sailed most of the races. A statistical meta-analysis on the comparison between the forecast issued using the ”Call Book” and measured data on the race areas is carried out, investigating the specific outcome of the strategy of the races with the forecasted meteorological data.
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| 2. |
- Banks, J., et al.
(författare)
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Assessing Human-Fluid-Structure Interaction for the International Moth
- 2016
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Ingår i: Procedia Engineering. - : Elsevier Ltd. - 1877-7058. ; , s. 311-316
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Konferensbidrag (refereegranskat)abstract
- The International Moth is an ultra-lightweight foiling dinghy class. Foil deflections and dynamic sailor-induced motions are identified as two key areas relating to foiling moth performance that are currently ignored in Velocity Prediction Programs (VPP). The impact of foil deflections is assessed by measuring the tip deflection and twist deformation of a T-foil from an International Moth. The full field deformation due to an applied load is measured using Digital Image Correlation (DIC). The foil's structural properties can then be determined based on the measured structural response. The deformations are then calculated for an estimated steady sailing force distribution on the T-foil and their impact on performance is evaluated. To investigate the impact of dynamic sailor motions a system is developed that allows a sailor's dynamic pose to be captured when out on the water by determining the orientations of key body segments using inertial sensors. It is validated against measured hiking moments and is demonstrated to work out on the water whilst sailing. Both these studies pave the way towards developing a Dynamic VPP for the international Moth, which can include unsteady human and foil interactions.
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| 3. |
- Banks, J., et al.
(författare)
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Assessment of Digital Image Correlation as a method of obtaining deformations of a structure under fluid load
- 2015
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Ingår i: Journal of Fluids and Structures. - : Academic Press. - 0889-9746 .- 1095-8622. ; 58, s. 173-187
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Tidskriftsartikel (refereegranskat)abstract
- Digital Image Correlation (DIC) is employed for the measurement of full-field deformation during fluid-structure interaction experiments in a wind tunnel. The methodology developed for the wind tunnel environment is quantitatively assessed. The static deformation error of the system is shown to be less than 0.8% when applied to a curved aerofoil specimen moved through known displacements using a micrometre. Enclosed camera fairings were shown to be required to minimise error due to wind induced camera vibration under aerodynamic loading. The methodology was demonstrated using a high performance curved foil, from a NACRA F20 sailing catamaran, tested within the University of Southampton RJ Mitchell, 3.5. mx2.4. m, wind tunnel. The aerodynamic forces induced in the wind tunnel are relatively small, compared with typical hydrodynamic loading, resulting in small deformations. The coupled deflection and blade twist is evaluated over the tip region (80-100% Span, measured from the root) for a range of wind speeds and angles of attack. Steady deformations at low angles of attack were shown to be well captured however unsteady deformations at higher angles of attack were observed as an increase in variability due to hardware limitations in the current DIC system. It is concluded that higher DIC sample rates are required to assess unsteady deformations in the future. The full field deformation data reveals limited blade twist for low angles of attack, below the stall angle. For larger angles, however, there is a tendency to reduce the effective angle of attack at the tip of the structure, combined with an unsteady structural response. This capability highlights the benefits of the presented methodology over fixed-point measurements as the three dimensional foil deflections can be assessed over a large tip region. In addition, the methodology demonstrates that very small deformations and twist angles can be resolved.
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| 4. |
- Guida, Pierluigi, et al.
(författare)
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Three-dimensional variations of the Nacra 17 main foil for benchmarking shape optimizations
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Optimising a three-dimensional foil is becoming an essential part of the design process of high-performance sailing vessels. With the advent of foiling in the America’s Cup in 2013 and the subsequent interest in foiling, the Olympic committee decided that the NACRA 17, a high-performance catamaran already present in the 2016 Rio Olympics, was to start foiling for the 2020 Tokyo Olympic Games. The objective of this research is to explore the hydrodynamic performance variations of the NACRA 17 Z-foil by means of Computational Fluid Dynamics (CFD) simulations, analysing in detail the current design and the possible improvements that could be made to achieve a better performing boat. Exploring changes in the three-dimensional design leads to the understanding that small foil modifications provide similar or higher performances than the current design without affecting the functional requirements of the NACRA 17 class such as the general deck layout. Because small local changes in foil shape could have a large effect on performance, foil design optimization is especially effective for large numbers of shape variables [1]. Despite considerable research on aerodynamic and hydrodynamic shape optimization, there is no standard benchmark problem allowing researchers to compare results. The presented research addresses this issue by running a series of CFD simulations in order to compare the performances of different three-dimensional shapes and configuration arrangements.
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| 5. |
- Knudsen, Stig, et al.
(författare)
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Dynamic Fluid Structure Interaction of NACRA 17 Foil
- 2024
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Ingår i: Journal of Marine Science and Engineering. - 2077-1312. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- The NACRA 17 is a small foiling catamaran that is lifted out of the water by two asymmetric z-foils and two rudder elevators. This paper investigates how foil deflection affects not only foil performance but overall boat behaviour using a numerical Fluid Structure Interaction (FSI) model. The deformations are solved with a solid model based on the Finite Element Method (FEM) and the flow is solved with a Reynolds Average Navier-Stokes (RANS) based Finite Volume Model (FVM). The models are strongly coupled to allow dynamic FSI simulations. The numerical model is validated by comparing it to an experimental campaign conducted at the RISE SSPA Maritime Center in Sweden.Validation shows reasonable agreement, but the model can only be considered validated for some rake angles. The large deformation of the foils is found to have a profound effect on the performance of the foils and therefore of the overall catamaran. Turbulence transition and boat speed are found to affect foil forces and, in turn, deformation. Dynamic response of the foils during boat motion as exposed to waves is investigated and finally the full boat hydrodynamic is simulated by including both foils and the rudders in various scenarios.
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| 6. |
- Lidke, AK, et al.
(författare)
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Development of an America's Cup 45 tacking simulator
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the development of an AC45 simulator conducted as a student Master’s project at the University of Southampton. The main aim was to be able to asses and improve the tacking skills of the helm and the crew through systematic training. The physical interface of the simulator replicates the seating position of the helmsman and the main trimmer and the graphical representation provides the users with visual cues of the simulated boat, boundaries and marks for a sample race course. The theoretical model uses hydrodynamic manoeuvring coefficients based on empirical formulae and experimental data. The aerodynamic forces are pre-calculated using a full-scale RANS CFD simulation. The accuracy of the model is verified against the AC45 racing tracking data to ensure that the speed loss during a tack, experienced by the users of the simulator, is as close to reality as possible. The ultimate aim of the project was to study the potential of the simulator to assess and train the crews, improving their skill in tacking the boat effectively. This has been done by examining the performance of two groups of users over a series of practice sessions. The simulator could be potentially used for training the helmsmen of the Youth America’s Cup Red-Bull teams, which have limited budgets, training days and sailing experience compared to the professional AC sailors.
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| 7. |
- Lidstrom, D, et al.
(författare)
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Agent based match racing simulations : Starting practice
- 2022
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Ingår i: SNAME 24th Chesapeake Sailing Yacht Symposium, CSYS 2022. - : Society of Naval Architects and Marine Engineers.
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Konferensbidrag (refereegranskat)abstract
- Match racing starts in sailing are strategically complex and of great importance for the outcome of a race. With the return of the America's Cup to upwind starts and the World Match Racing Tour attracting young and development sailors, the tactical skills necessary to master the starts could be trained and learned by means of computer simulations to assess a large range of approaches to the starting box. This project used game theory to model the start of a match race, intending to develop and study strategies using Monte-Carlo tree search to estimate the utility of a player's potential moves throughout a race. Strategies that utilised the utility estimated in different ways were defined and tested against each other through means of simulation and with an expert advice on match racing start strategy from a sailor's perspective. The results show that the strategies that put greater emphasis on what the opponent might do, perform better than those that did not. It is concluded that Monte-Carlo tree search can provide a basis for decision making in match races and that it has potential for further use.
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| 8. |
- Marimon Giovannetti, Laura, et al.
(författare)
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APPENDAGES INVESTIGATION AND THEIR EFFECTS ON MANEUVERING COEFFICIENTS FOR APPLICATIONS IN WIND ASSISTED SHIPS
- 2020
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Konferensbidrag (refereegranskat)abstract
- When designing a hull that needs to account for sails, either rigid or flexible, it is necessary to consider the larger leeway and heel angles deriving from the sails side-forces compared to a traditional ship. It is therefore necessary to explore the possibility of adding appendages to the hull to balance those forces, achieving an optimum trade-off between hydrodynamic efficiency and manoeuvrability. The possibility of numerically simulating the manoeuvre coefficients at design stage will increase the chances of understanding the behaviour of a ship from an early stage in the design process. The current research is based on the evaluation of hydrodynamic efficiency and manoeuvre coefficients of a hull with rudders and shafts in a pure resistance, self-propulsion and in a wind-assisted mode. Having assessed the performances of the vessel with a Velocity Prediction Program (VPP), an in-depth research on suitable appendages was performed to reduce the experienced leeway angle, and ultimately increase the performances of a wind-assisted ship, especially when subject to wind angles ranging between 40 and 80. Many CFD simulations were initially performed to assess the hydrodynamic characteristics of the hull in a range of flow directions, rudder angles, ship speed and combinations. Those simulations encompass the whole range of datapoint needed to describe the forces and moments acting on a wind-assisted ship, simulating a towing-tank captive test, namely performing a Virtual Captive Test (VCT) [1]. Three types of possible appendages used to increase the generated side-force of the wind-assisted vessel are further investigated and the advantages and disadvantages are described. The findings of those preliminary simulations are then used as a basis for a structured model testing campaign.
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| 9. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Developing fluid structure interaction experimental methodologies For dynamic foil measurements
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The ability to validate computational predictions of either passive adaptive or dynamic response of deformable foils is essential when seeking to optimise high performance yachts. This requires time-accurate and synchronised measurements of the flow field and the shape of the deformable foil. It is important to understand the accuracy with which the onset of dynamic effects such as flutter or stall can influence the structural design and planform. Examples of such design challenges are present in the design of hydrofoils, wing sails and other propulsion systems such as composite propellers. The current research aims to demonstrate the capability of an experimental methodology that can be used as a validation for numerical investigations of dynamic fluid-structure interaction problems. The presented methodology provides high-speed full-field experimental data of: the structural deformations, by means of Digital Image Correlation (DIC), the tip vortex flow field, by means of Particle Image Velocimetry (PIV) and the forces and moments acting on a flexible aerofoil. A comparison between static and dynamic lift coefficients is presented for unsteady dataset and the effect of dynamic loads are analysed both at structural deformation and flow features level. Overall it is found that it is possible to capture synchronised structural deformation and flow field data at reasonable data rates that allow validation assessment of unsteady CFD.
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| 10. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Developing tools for assessing the fluid structure interaction of passive adaptive composite foils
- 2016
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Ingår i: Insights and Innovations in Structural Engineering, Mechanics and Computation - Proceedings of the 6th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2016. - Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 : CRC Press/Balkema. - 9781138029279 ; , s. 586-591
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Konferensbidrag (refereegranskat)abstract
- The study presents an experimental and numerical evaluation of bend-twist elastic coupling in composite passive-adaptive structures. Due to the lack of experimental validation in Fluid Structure Interaction (FSI) investigations, a full-field deformation of an aerofoil-shaped section under wind loading is measured. The experimental analysis is carried out at the University of Southampton 3.5 m × 2.4 m R. J. Mitchell wind tunnel using full-field non-contact measurement techniques such as high speed three dimensional Digital Image Correlation (DIC) and stereoscopic Particle Image Velocimetry (PIV). After assessing the validity and repeatability of the experiments, the study focuses on the development of a numerical FSI investigation that involves the use of a structural and a fluid solver to simulate the aero-elastic behaviour of composite tailored structures with different lay-up arrangements. The numerical analysis is developed as a design tool to allow the structure investigated to maximise bend-twist coupling under increased aerodynamic loading.
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| 11. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Developing tools for assessing the Fluid Structure Interaction of Passive Adaptive Composite foils
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The study presents an experimental and numerical evaluation of bend-twist elastic coupling in composite passive-adaptive structures. Due to the lack of experimental validation in Fluid Structure Inter-action (FSI) investigations, a full-field deformation of an aerofoil-shaped section under wind loading is measured. The experimental analysis is carried out at the University of Southampton 3.5 m x 2.4 m R. J. Mitchell wind tunnel and involves the use of full-field non-contact measurement techniques such as high speed three dimensional Digital Image Correlation (DIC) and stereoscopic Particle Image Velocimetry (PIV). After assessing the validity and repeatability of the experiments, the study focuses on the development of a numerical FSI investigation that involves the use of a structural and a fluid solver to simulate the aero-elastic behaviour of composite tailored structures with different lay-up arrangements. The numerical analysis is developed as a design tool to allow the structure investigated to maximise bend-twist coupling under increased aerodynamic loading.
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| 12. |
- Marimon Giovannetti, Laura, et al.
(författare)
-
FLUID STRUCTURE INTERACTION DESIGN DEVELOPMENT OF PASSIVE ADAPTIVE COMPOSITE INTERNATIONAL MOTH FOIL
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The International Moth is a single-handed ultra-lightweight foiling development class boat, and it follows open class rules. Therefore, the designer and builder have full liberty to develop and produce the fastest boat [1]. It is possible to adapt the internal structure of the fixed foil to achieve a tailored twist angle for a given load. Exploring the possibility of using Passive Adaptive Composite (PAC) on the moth hydrofoil to control its pitch angle enables the boat to achieve a stable flight in a wide range of weather conditions whilst reducing the induced drag, passively decreasing the angle of attack in increased boat speed. Using PAC in a multi-element foil, such as the International Moth one, will allow the structure to achieve a constant lift force with speeds higher than the design take-off speed with less need to constantly modifying the rear foil section. Toward the development of a PAC moth fixed foil, experimental and numerical results for a single element aerofoil, able to achieve a linear decrease in lift coefficient with increase in wind speed, are presented and discussed. The results present the aero-elastic response of the foil explaining the complexity involved in fluid-structure interaction problems.
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| 13. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Fluid structure interaction in high performance catamaran C-foils under load
- 2015
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Ingår i: 5th High Performance Yacht Design Conference, HPYD 2015. - : Royal Institution of Naval Architects. ; , s. 171-179
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Konferensbidrag (refereegranskat)abstract
- An experimental technique to accurately quantify the deformation and the bend-twist coupling of high performance composite foils under fluid loading is presented. The experimental results are reproduced in a Computational Fluid Dynamic (CFD) environment to assess the impact of board deflection and changes in pitch angle on vertical force generated in the C-foils while sailing under increased hydrodynamic pressure. A three dimensional Digital Image Correlation (DIC) methodology suitable for use within a wind tunnel is developed. The technique allows for the measurement of full-field deflection during fluid-structure interaction (FSI) experiments. Combined with DIC technique, the C-foil tip vortex is investigated using Particle Image Velocimetry (PIV) to correlate the variation of the vortex position and strength to the deflection of the board. These techniques, combined with CFD investigations allow potential changes in structural behaviour to be assessed with regard to improving the performances of the foils in sailing conditions. Experimental results are presented for a high performance curved foil from a NACRA F20 catamaran tested within the University of Southampton RJ Mitchell wind tunnel. The fluid regime is chosen to have a Reynolds number equivalent to light upwind sailing conditions (Rn=6.66x105 : boat speed of 6 knots) with a fifth of the fluid loading experienced in the water. Curved foils provide both a hydrodynamic side-force to counteract the aerodynamic forces of the sails and a vertical lift force to reduce the wetted surface area and hence the resistance. It is therefore necessary to investigate from a sailor point of view the influences of the side force and vertical coefficients that the change in effective angle of attack and of pitch will give to the stability and the performances of the catamaran.
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| 14. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Fluid-Structure Interaction of a Foiling Craft
- 2022
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Ingår i: Journal of Marine Science and Engineering. - : MDPI. - 2077-1312. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- 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. © 2022 by the authors.
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| 15. |
- Marimon Giovannetti, Laura
(författare)
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Fluid structure interactiontesting, modelling and development of Passive Adaptive Composite foils
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High performance foiling catamarans are one of the fastest growing sectors in the sailing and sport industries, allowing athletes to perform in extremely fast and spectacular boats. These boats fly above the water with the aid of foils that not only provide horizontal side-force to counterbalance the aerodynamic forces from the sails, but also deliver vertical force that supports some or all of the mass of the boat. Exploring the possibility of using Passive Adaptive Composite (PAC) on the hydrofoils to control their pitch angle enables the boats to achieve a stable flight in a wide range of weather conditions. This thesis presents an experimental and numerical evaluation of bend-twist elastic coupling in composite passive-adaptive structures. Due to the lack of experimental validation in Fluid Structure Interaction (FSI) investigations, a full-field deformation of an aerofoil-shaped section under wind loading is measured. Moreover, the influences of structure deflection on flow behaviour are investigated by looking at the changes in flow features evaluated on a transverse plane downstream of the trailing edge. The experimental analysis was carried out at the University of Southampton R. J. Mitchell wind tunnel and involved the use of full-field non-contact measurement techniques such as high speed three dimensional Digital Image Correlation (3-D DIC) and stereoscopic Particle Image Velocimetry (PIV). After assessing the validity and repeatability of the experiments, the research focuses on the development of a numerical FSI investigation that involves the use of a structural and a fluid solver to simulate the aero-elastic behaviour of composite tailored specimens with different internal structures. The numerical analysis is developed as a tool to allow the design of a new structure able to achieve a constant level of lift force (corresponding to the weight of the catamaran) in increased flow speed. During the research project it was proven that the efficiency of the foils can be improved by tailoring the internal structure to induce smart coupled bend-twist toward a wash-out (feather) or wash-in (stall) position under increased loading
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| 16. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Investigation of tacking strategies using an America's Cup 45 catamaran simulator
- 2014
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Ingår i: Procedia Engineering. - : Elsevier Ltd. - 1877-7058. ; , s. 811-816
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Konferensbidrag (refereegranskat)abstract
- The recent America's Cup has demonstrated the extreme performance capability of the AC45 and AC72 catamarans. The high cost and risk of catastrophic failure has imposed restrictions on the availability of these boats for training. As a consequence the use of simulators to allow shore-based training becomes an attractive option. The aim of this study is to use a recently developed AC45 tacking simulator to investigate the optimum tack sequence by conducting a parametric study of user control inputs based on previously recorded time histories. The study will provide a better understanding of the influence of the input parameters on the tack and allow improved shore-based training programmes to be developed.
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| 17. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Multi-wing sails interaction effects
- 2022
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Ingår i: SNAME 24th Chesapeake Sailing Yacht Symposium, CSYS 2022. - : The Society of Naval Architects and Marine Engineers.
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Konferensbidrag (refereegranskat)abstract
- The effects of multiple wings interacting and the change in efficiency due to those effects as well as optimal sheeting angles are becoming an important area of study with the advent of wind-propelled ships for goods transport. This research presents a first analysis of wind tunnel tests carried out at the University of Southampton R.J. Mitchell wind tunnel where three wings are subject to turbulent flow with Reynolds number in excess of 1 million. A range of possible variations of ship heading and apparent wind angles are tested taking into consideration the blockage effects and the geometrical characteristics of the working section. The forces and moments are captured on each individual wing as well as in the overall wind tunnel balance with 6-components dynamometers. Furthermore, pressure sensors and PIV data are recorded during the tests to provide the experimental campaign with results that can validate both qualitatively and quantitatively the numerical tools developed to aid the design stage of wind propelled vessels.
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| 18. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Review of undewater fluid-structure interaction measuring techniques
- 2021
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Ingår i: 7th High Performance Yacht Design Conference, HPYD 2021. - : The Royal Institution of Naval Architects.
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Konferensbidrag (refereegranskat)abstract
- This research aims to provide a feasibility study for an underwater Fluid Structure Interaction (FSI) experimental methodology. The possibility of measuring a structural deflection under fluid load and the flow behaviour around the structure is particularly interesting with the rise of composite materials, due to their inherent flexibility that permits them to be designed to a range of loading conditions. A review study on the experimental methodology available is carried out so that, in the future, a FSI measurement system can be installed in an underwater environment such as a towing tank or a marine basin. A robust and repeatable experimental methodology will also provide researchers with a validation case for numerical FSI simulations. The feasibility study starts with a thorough investigation of the existing measuring systems with an assessment of what could be used in SSPA Sweden underwater facilities (i.e. towing tank and marine dynamics laboratory). Currently there is a lack of FSI experimental methods, especially for underwater environment. The large majority of the current studies does not account for the complexity of the FSI coupled problems, where the structural response affects the flow behaviour and vice-versa. Bringing different techniques together will allow simultaneous measurements to be taken in a dynamic underwater environment. This would be especially important for performance prediction and numerical codes validations of foiling structures to assess the effects of deflections and twist when phenomena like cavitation and ventilation occur.
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| 19. |
- Marimon Giovannetti, Laura, et al.
(författare)
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The art of model testing: Using CFD to adapt traditional tank testing techniques to a new era of wind propelled shipping
- 2020
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Konferensbidrag (refereegranskat)abstract
- Hybrid testing is an experimental technique that can be used to test ships and marine structures when both hydrodynamic and aerodynamic effects are important, for example for wind powered or wind assisted ships and sailing vessels. SSPA is currently developing an experimental method using hybrid testing involving fan forces added to ship decks to simulate sails to assess the course keeping, seakeeping and manoeuvring performance of a wind powered ship. For conventional motor ships there are well established test methods and knowledge on how to scale the results from model to full-scale. For a wind propelled ship however, the driving force is no longer located at the propeller shaft but high above deck and at another longitudinal position that could vary with true wind angle and speed. Moreover, there is a large side force coming from the aerodynamic forces of the wingsails that needs to be counteracted with lifting surfaces underwater. The side-force and yaw moment are much more prominent than in conventional vessels. The combination of those factors will influence the manoeuvrability and course keeping, especially in waves. Having built up the research tools for predicting and simulating the behaviour of a full-scale vessel, making the model sail in a similar way as predicted for the full-scale vessel remains a challenge because of the difference between Froude scaling and Reynolds scaling applicable for the hull and lifting surfaces respectively. Using Computational Fluid Dynamics (CFD) to understand the scale effects in model tests for a wind powered ship and developing a methodology for determining the fan parameters that correctly model the ships behaviour and performance are the key objectives of the research study. The art of model testing encompasses the need to learn from different techniques to ultimately achieve the best agreement between model tests and full-scale results in terms of accuracy, repeatability, cost, and speed. Learning from preliminary experimental tests, through studies on CFD and ultimately paving the way to new testing methodologies is the main aim of the current paper.
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| 20. |
- Marimon Giovannetti, Laura, et al.
(författare)
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The effects of hydrodynamic forces on maneuvrability coefficients for wind-assisted ships
- 2020
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Ingår i: ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering (OMAE2020). - 9780791884379
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Konferensbidrag (refereegranskat)abstract
- Assessing the manoeuvring performances of a ship at a design stage is becoming more important, especially when trying to improve shipping efficiency to reduce fuel consumption. When designing a hull with appendages, it is necessary to balance hydrodynamic efficiency with manoeuvrability. Therefore, the possibility of simulating a captive test at a design stage will increase the chances of understanding the behaviour of a ship from an early stage in the design process. The current research is based on the evaluation of hydrodynamic efficiency of a hull and appendages in a pure resistance, self-propulsion and in a wind-assisted mode. The forces and moments acting on the hull and appendages are then analysed and used as inputs for a Virtual Captive Test (VCT) [1]. In order to correctly perform a VCT and further analyse the performances of a ship with a Velocity Prediction Programme (VPP), particular care has been put in correctly capturing the manoeuvrability coefficients. Those are derived with polynomial fittings once the forces and moments acting on the ship are extracted from the Computational Fluid Dynamics (CFD) simulations. Many CFD simulations were performed to assess the hydrodynamic characteristics of the hull and appendages in a range of flow directions, rudder angles and rotating flow. Those simulations encompass the whole range of datapoints needed to describe a wind-assisted ship during manoeuvring. Taking into consideration both hydrodynamic characteristics and manoeuvrability effects at an early design stage can reduce model tests costs and will allow to inspect a larger number of hull-appendages scenarios when analysing the final VPP results.
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| 21. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Toward the development of a hydrofoil tailored to passively reduce its lift response to fluid load
- 2018
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 167, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this research is to explore the possibility of using Passive Adaptive Composite (PAC) on structures to help control the lift generated by hydrofoils on boats such as the International Moth. Introducing composite fibres oriented at off-principal axis angles, allow a foil to passively control its pitch angle to reduce the lift generated at higher boat speeds helping to achieve a stable flight in a wide range of weather conditions. PAC utilises the inherent flexibility of a composite structure to induce a twist response under bending load which could be used to minimise the use of active control systems, or even improve the dynamic response of foils in waves. However, to design flexible foils requires numerical and experimental tools to assess the complex fluid structure interactions involved. This paper evaluates a simplified hydrofoil geometry designed to reduce its lift coefficient with increased flow speed. A coupled Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) methodology is presented to predict flexible foil performance. Validation of these numerical tools is achieved through the use of wind tunnel experiments including full field deformation measurements. Twist deformations resulted in a reduction in the effective angle of attack by approximately 30% at higher flow speeds reducing the foil lift and drag significantly
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| 22. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Uncertainty assessment of coupled Digital Image Correlation and Particle Image Velocimetry for fluid-structure interaction wind tunnel experiments
- 2017
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Ingår i: Journal of Fluids and Structures. - : Academic Press. - 0889-9746 .- 1095-8622. ; 68, s. 125-140
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Tidskriftsartikel (refereegranskat)abstract
- The development of advanced composite structures for maritime and aerospace applications requires the ability to quantify their actual performance under known fluid loads. One example is the need to investigate the differences in fluid–structure response of passive adaptive composite structures. A wind tunnel based method is used to quantify the structural behaviour, and fluid response, of a flexible aerofoil under fluid loading. The technique measures the deflection of the structure, with high speed stereoscopic Digital Image Correlation (DIC). The tip vortex position is measured using high resolution stereoscopic Particle Image Velocimetry (PIV). The accuracy of the two full-field optical measurement systems is quantified and the effect of optical interactions is assessed. A flexible NACA0015 rectangular plan-form aerofoil of 0.9 m span and aspect ratio of two is subjected to aerodynamic loading within a closed circuit wind tunnel. The wind speed was varied from 10 to 25 m/s within a 3.5 m x 2.4 m working section. The structural response is measured simultaneously with the fluid flow field around the tip vortex. The tip vortex core, which moved by ≈62 mm at the highest wind speed, is directly compared to the deformation of the structure, which deflected by ≈58 mm. A maximum foil twist of ≈0.6° was observed. The DIC accuracy is evaluated in static and transient conditions for translational and rotational movement. The DIC maximum error for translations, greater than or equal to 0.5 mm, is less than 3% and less than 0.6% in dynamic motions. The DIC total error for rotations is less than 5% in static motions and 1% in dynamic rotations. The PIV uncertainty is quantified a posteriori providing the errors due to the correlation algorithm and the experimental setup. The mean in-plane velocity component uncertainties in the vortex region varied between 1.2% and 3.5% depending on flow speed (≈0.1 px). The mean out-of-plane velocity uncertainty around the vortex varies between 2% and 3.3% depending on flow speed
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| 23. |
- Marimon Giovannetti, Laura, et al.
(författare)
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Variation of underwater appendages and their effects on wind powered ships
- 2021
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Ingår i: 7th High Performance Yacht Design Conference, HPYD 2021. - : The Royal Institution of Naval Architects.
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Konferensbidrag (refereegranskat)abstract
- Assessing the manoeuvring performances of a ship early in the design stage is becoming ever more important, especially now that wind-assisted propulsion is radically increasing in popularity as a measure to reduce fuel consumption. For conventionally propelled vessels most of the forces are in the longitudinal direction. Some, relatively small, drift angles and rudder angles are encountered in order to compensate for side forces due to environmental conditions. For a wind-propelled vessel on the other hand, side forces are an inevitable consequence of the propulsion choice and it is of utmost importance to balance these side forces with a matching hydrodynamic design to efficiently propel the vessel forward avoiding travelling for longer periods of time. In order to counteract those large side forces, it is necessary to add underwater appendages. Their position along the hull will determine the centre of lateral resistance (CLR) that needs to be related to the aerodynamic centre of effort (CoE) in order to achieve a balanced ship. The research herein described, compares towing tank captive tests with Virtual Captive Tests (VCT) derived from Computational Fluid Dynamics (CFD) simulations and the effects of generated side forces and moments when the inflow angles are varied. Adding a set of diagonal foils to the hull, in the investigated case reduces the leeway angle of approximately 2 degrees in close-hauled conditions.
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| 24. |
- Olsson, Fredrik, et al.
(författare)
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A Performance Depowering Investigation for Wind Powered Cargo Ships Along a Route
- 2020
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Ingår i: Journal of Sailing Technology. - : The Society of Naval Architects and Marine Engineers. - 2475-370X. ; 5:1, s. 47-60
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Tidskriftsartikel (refereegranskat)abstract
- For a sailing yacht, depowering is a set of strategies used to limit the sail force magnitude by intentionally moving away from the point of maximum forward driving force, potentially reducing the ship speed. The reasons for doing this includes among others; reduction of quasi-static heeling angle, structural integrity of masts and sails and crew comfort. For a wind powered cargo ship, time spent on a route is of utmost importance. This leads to the question whether there is a performance difference between different depowering strategies and if so, how large. In this research, a wind-powered cargo vessel with rigid wings is described in a Velocity Prediction Program (VPP) with four-degrees of freedom, namely surge, sway, roll and yaw, with a maximum heel angle constraint. The resulting ship speed performance for different depowering strategies are investigated and the implications in roll and pitch-moments are discussed. The wind conditions when depowering is needed are identified. A statistical analysis on the probability of occurrence of these conditions and the impact of the different depowering strategies on the required number of days for a round-trip on a Transatlantic route is performed.
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| 25. |
- Wielgosz, Chiara, et al.
(författare)
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CFD Study on the Different Stratifications of the Atmospheric Boundary Layer and Their Effect on the Performance of Wind Propelled Ships
- 2024
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Konferensbidrag (refereegranskat)abstract
- Computational Fluid Dynamics (CFD) simulations to predict forces from a Wind Propulsion Unit (WPU) on a ship hull are carried out to better understand the forces dependency on wind speed and angle. Three different Atmospheric Boundary Layer (ABL) stratifications, nominally unstable, neutral, and stable, are studied in a CFD environment to better understand how to reproduce these velocity profiles numerically and how much is their impact on the performance of a general ship’s hull equipped with a Flettner rotor. A series of 2D and 3D simulations with an empty domain are run to tune some numerical settings for a correct representation of the ABL. Simulations with a simplified hull and a Fletter rotor are run to purely analyse the differences between the profiles and their effects on a reproduceable geometry. The three different ABL profiles are tested for four different wind angles, producing an overview of the dependency of rotor and ship performance on wind speed profiles, wind angles and hull interaction. A clear impact of the wind profiles and the wind angle on the ship hull is visible on the rotor lift and drag coefficients, while in terms of ship performance, described by the ratio of the thrust and side force coefficients, the impact is limited
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