| 1. |
- Andersson, Anton, et al.
(författare)
-
Design of a Foiling Optimist
- 2018
-
Ingår i: Journal of Sailboat Technology. ; 2018, s. 1-24
-
Tidskriftsartikel (refereegranskat)abstract
- Because of the successful application of hydrofoils on the America's Cup catamarans in the past two campaigns the interest in foiling sailing craft has boosted. Foils have been fitted to a large number of yachts with great success, ranging from dinghies to ocean racers. An interesting question is whether one of the slowest racing boats in the world, the Optimist dinghy, can foil, and if so, at what minimum wind speed. The present paper presents a comprehensive design campaign to answer the two questions. The campaign includes a newly developed Velocity Prediction Program (VPP) for foiling/non-foiling conditions, a wind tunnel test of sail aerodynamics, a towing tank test of hull hydrodynamics and a large number of numerical predictions of foil characteristics. An optimum foil configuration is developed and towing tank tested with satisfactory results. The final proof of the concept is a successful on the water test with stable foiling at a speed of 12 knots.
|
|
| 2. |
- Andersson, A, et al.
(författare)
-
The Foiling Optimist
- 2017
-
Ingår i: The Proceedings of the 4th International Conference on Innovation in High Performance Sailing Yachts, Lorient, France, 28-30 June 2017.. ; , s. 19-30
-
Konferensbidrag (refereegranskat)
|
|
| 3. |
- Ekström, David, et al.
(författare)
-
Optimization of the Internal Structure and Shape of a 470 Dinghy Centerboard
- 2020
-
Ingår i: Proceedings (MDPI). - Basel Switzerland : MDPI. - 2504-3900. ; 49:1
-
Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to design an improved centerboard for the Olympic 470 sailing dinghy sailing upwind. The design is improved by introducing a composite design that makes the centerboard twist to windward when sailing upwind, thereby reducing the angle of attack of the hull. The results show that a beneficial twist up to 1.5° is possible to achieve without compromising the centerboard strength. According to our estimates, by utilizing the improved design it is possible to obtain a gain of up to 9 s per race in a world cup race.
|
|
| 4. |
- Marimon Giovannetti, Laura, et al.
(författare)
-
Multi-wing sails interaction effects
- 2022
-
Ingår i: SNAME 24th Chesapeake Sailing Yacht Symposium, CSYS 2022. - : The Society of Naval Architects and Marine Engineers.
-
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.
|
|
| 5. |
- Persson, Adam, 1991, et al.
(författare)
-
A time-domain model for unsteady upwind sail aerodynamics using the indicial response method
- 2024
-
Ingår i: Ocean Engineering. - 0029-8018 .- 1873-5258. ; 299
-
Tidskriftsartikel (refereegranskat)abstract
- For the design of sailing vessels, the use of Dynamic Velocity Prediction Programs is expanding, as naval architects start to consider the effects of waves and varying wind conditions in order to design faster, safer and more efficient vessels. Many models that predict the unsteady hydrodynamic response are available, but for sail aerodynamics, few models have been presented, and the quasi-steady assumption is instead commonly used. The aim of this paper is to develop a time-domain model for unsteady sail aerodynamics that can handle arbitrary motions and requires only limited input. The proposed model is based on the Indicial Response Method, with specific adaptations to handle the additional complexity of sail aerodynamics. The model's predictive performance is evaluated against URANS CFD results for several cases of increasing complexity. This includes a 3D upwind sail plan subjected to pitching motion, where comparisons are also made with the common quasi-steady (Q-S) assumption. Compared to this, the proposed model delivers significantly better predictions for the amplitude of lift, thrust and sideforce. However, the drag amplitude is over-predicted by the model, and as a result, there is a significant misprediction of thrust phase. While there is a need to improve the prediction of unsteady drag, this paper shows that the model represents a significant improvement over the Q-S assumption, for unsteady performance prediction on timescales shorter than the wave period.
|
|
| 6. |
- Persson, Adam, 1991, et al.
(författare)
-
An improved procedure for strongly coupled prediction of sailing yacht performance
- 2020
-
Ingår i: InnovSail 2020 Proceedings. ; 6:1, s. 133-
-
Konferensbidrag (refereegranskat)abstract
- In this paper, an improved procedure for strongly coupled prediction of sailing yacht performance is developed. The procedure uses 3D RANS CFD to compute the hydrodynamic forces. When coupled to a rigid body motion solver and a sail force model, along with a rudder control algorithm, this allows sailing yacht performance to be predicted within CFD software. The procedure provides faster convergence when compared to previously published methods. The grid motion scheme, partially using overset grid techniques, means that correct alignment between the free surface and the background grid is ensured even at large heel angles. The capabilities are demonstrated with performance predictions for the SYRF 14 m yacht, at one true wind speed, over a range of true wind angles, with one up- and one downwind sailset. The results are compared to predictions from the ORC-VPP for a yacht with similar main particulars.
|
|
| 7. |
- Persson, Adam, 1991, et al.
(författare)
-
CFD prediction of steady and unsteady upwind sail aerodynamics
- 2017
-
Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 141, s. 543-554
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, RANS CFD simulations of steady and unsteady upwind sail aerodynamics are verified and validated against wind tunnel experiments previously performed at Politecnico di Milano. Experimental data is presented, and the experimental results are analysed to estimate repeatability. Blockage effects caused by tunnel boundary layers and measurement equipment are estimated using detailed CFD simulations, allowing such effects to be accounted for. A verification procedure is performed, resulting in very low numerical uncertainties.The force predictions are then validated for both steady and unsteady conditions. The steady results show verygood agreement, with a maximum error of 3.1%. For the unsteady conditions, good agreement is found for theforce mean values, whilst the prediction of force amplitudes is less satisfactory.
|
|
| 8. |
- Persson, Adam, 1991
(författare)
-
Dynamic effects on yacht sails and rudders
- 2019
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In search of increased performance, modern sailing vessels are becoming more and more complex, introducing additional challenges in the design process. The dynamic behaviour of the vessel is of great importance to safe and efficient operation and thus needs to be accounted for when evaluating the performance. To accomplish this, the forces acting on the vessel in dynamic conditions must be predicted and evaluated. The purpose of this thesis is to develop methods to predict the forces acting on sails and rudders in dynamic conditions. RANS CFD is used to predict upwind sail aerodynamic forces. A comprehensive study of the numerical setup, physical modelling and uncertainties in the CFD solutions is presented. The spatial discretisation uncertainty is shown to be low for steady conditions, and the forces are well predicted. For dynamic conditions, mean values are predicted with reasonable accuracy. However, the instantaneous quantities show more scatter and a higher comparison error. Following careful analysis of the numerical simulations and experimental procedures, possible error sources are identified. For example, in the post-processing of experimental measurements, added mass forces had been removed incorrectly. For the numerical simulations, poor performance of the turbulence model may explain the error. The dynamic characteristics of rudders for the Finn dinghy are investigated using full-scale towing tank tests. Considerable differences in both performance and handling are revealed. Also, the study highlights challenges faced when performing experimental testing of dynamic effects, such as the introduction of artificial constraints. The prediction of dynamic effects introduces additional uncertainties, regardless of whether experimental or numerical techniques are utilized, that need to be carefully controlled. Further studies are proposed to investigate these.
|
|
| 9. |
|
|
| 10. |
- Persson, Adam, 1991, et al.
(författare)
-
Performance evaluation and ranking of 7 rudders for the Finn dinghy
- 2018
-
Ingår i: Journal of Sailing Technology. - 2475-370X. ; 3:1, s. 1-
-
Tidskriftsartikel (refereegranskat)abstract
- As a follow up to the Olympic Games, commercially available Finn dinghy rudders were tested to determine their hydrodynamic performance. Seven rudders were tested, out of the nine different rudder models that were measured for competition at the 2016 Olympic Games, thus representing a large portion of the rudders used by sailors. The remaining two rudder models could not be tested, since they are of semi-custom or custom design or manufacture. Each rudder was tested in seven different conditions, selected to cover a wide range of sailing conditions. The testing revealed considerable differences, both in performance and handling.
|
|
