| 1. |
- Magnander, Gustaf, et al.
(författare)
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Wind-Tunnel Investigation of the ILCA 7 Mk II Sail in Downwind Conditions
- 2023
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Ingår i: Proceedings of 6th International Conference on Innovation in High Performance Sailing Yachts and Wind Assisted Ships. ; 8:1, s. 118-142
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Konferensbidrag (refereegranskat)abstract
- Aerodynamic coefficients from wind-tunnel tests are presented for the ILCA 7 in all six degrees of freedom. Two apparent wind speeds are considered: a light wind case corresponding to 4 m/s at full scale and a strong wind case corresponding to 7 m/s. The light wind tests comprise five apparent wind angles, seven sheet angles, three kicker trims and three heel angles. For the strong wind case the dinghy is assumed sailing upright and only dead downwind, but with four sheet angles and three kicker trims. The scale is 1/7, which gives a reasonable blockage in the wind-tunnel. Blockage corrections are obtained using CFD. Correct scaling of the sail stretch, and mast bend is achieved with the full-scale sail cloth and a solid stainless-steel mast exposed to a wind speed √7 times larger than at full-scale. However, the Reynolds number is √7 times smaller. The main result of the investigation is the comprehensive data set, which is available on a public server. This data can be used in a VPP to optimise downwind sailing in smooth water. Several interesting conclusions can also be drawn directly from the data. Thus, for the light wind case the best sheet angle is 90 degrees regardless of the course sailed. However, for the strong wind case (dead downwind), the best angle is 80 degrees. In all cases the tight kicker trim produces the largest drive force and in the light wind case also the smallest side force.
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| 2. |
- Sundin, Maria, 1965, et al.
(författare)
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Space Sports - Sailing in Space
- 2016
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Ingår i: Proceedings from icSports 2016, 4th International Conference on Sport Sciences Research and Technology Support, Porto, Portugal, 7-9 november 2016. - : SCITEPRESS - Science and Technology Publications. - 9789897582059 ; , s. 141-146
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Konferensbidrag (refereegranskat)abstract
- Titan is the largest moon of Saturn, and apart from the Earth it is the only body in our solar system where a liquid exists on the surface. Within the last ten years a system of lakes and rivers have been discovered. The climate and seasonal cycles of Titan are still not very well known, but the composition and pressure are fairly well established. Perhaps in the future boats will sail the lakes of Titan for research purposes or even sport. The purpose of this paper is to give an overview of the concept of space sports, the conditions of Titan and to calculate important parameters of sailing such as floatability, stability, hull resistance and sail forces. This paper shows that if a sailing yacht on Titan will have twice as large displacement as on Earth, it will be 2.6 times less stable for the same beam. Since friction will be smaller, it will be faster than on Earth at low speed, but significantly slower at high speeds due to the wave generation. The same sail area is required to get the same sail forces if the average wind is 3 m/s, while a 9 times larger sail area is required for if the wind speed is only 1 m/s.
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| 3. |
- Malmek, Karolina, 1990, et al.
(författare)
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Rapid aerodynamic method for predicting the performance of interacting wing sails
- 2024
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- Rapid performance prediction tools are required for the evaluation, optimization, and comparison of different wind propulsion systems (WPSs). These tools should capture viscous aerodynamic flow effects in 3D, particularly the maximum propulsion force, stall angles, and interaction effects between the lift-generating units. This paper presents a rapid aerodynamic calculation method for wing sails that combines a semiempirical lifting line model with a potential flow-based interaction model to account for 3D interaction effects. The method was applied to a WPS that consisted of several wing sails with considerable interaction effects. The results were compared to CFD RANS simulations in 2D and in 3D. For the evaluated validation cases, the interaction model improved the prediction considerably compared to when the interaction was not accounted for. The method provided acceptable driving force, moments, and stall predictions, with negligible computational cost compared to 3D CFD simulations.
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| 4. |
- Sundin, Maria, 1965, et al.
(författare)
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Vi ska segla i metan på Titan
- 2016
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Ingår i: Forskning & Framsteg. - : Forskning & Framsteg. - 0015-7937. ; 2016:7, s. 42-47:7, s. 42-47-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Orych, Michal, 1979, et al.
(författare)
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Roughness effect modelling for wall resolved RANS – Comparison of methods for marine hydrodynamics
- 2022
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 266
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with several aspects of surface roughness modelling in RANS codes applied to full-scale ship simulations. To select a method that is suitable for wall-resolved RANS solvers and gives reliable results at high Reynolds numbers, five different roughness models are compared. A grid uncertainty analysis is performed and the sensitivity to the grid resolution close to the wall (y+) is investigated. The results are compared to extrapolated results of experiments carried out with rough plates with various heights and roughness types. A correlation factor between the Average Hull Roughness and the equivalent sand roughness height is investigated, and a value of five is deemed the most suitable. The work suggests that the Aupoix-Colebrook roughness model gives the best results for full-scale ship simulations, at least with the current code, and that the near-wall grid resolution required for smooth surfaces can be applied also for the rough case. © 2022 The Authors
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| 6. |
- Prabahar, N. S. S., et al.
(författare)
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Split-flaps for increased heel stability of t-foil configurations
- 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
- Horizontal T-foils allow for maximum lift generation within a given span. However, for T-foils, the lift force acts in the symmetry plane of the boat, thereby producing no righting moment. It results in a lack of transverse stability during foil-borne sailing. In this project, we propose a system, where the height-regulating flap on the trailing edge of the foil is split into a port and a starboard flap, whose angle is adjusted proportionally to the heel. Such a system generates and scales the righting moment based on the heel angle, making the boat easier to balance. The effectiveness of this system is studied for a custom-made double-handed skiff using a dynamic velocity prediction program (DVPP), especially in the take-off phase. It is shown that the split flap system generates a larger righting moment for the foiling boat than for the non-foiling one at boat speeds above 3 m/s.. The improved stability comes at a cost of additional induced resistance and this effect is computed by CFD. It is shown, using the DVPP, that the increased resistance, slows down the boat at the lowest wind speeds, but above 2.5 m/s true wind, the split flap boat is as fast as the boat with a single flap around the racecourse. Due to the higher stability, less depowering of the sails is required, and that compensates for the increased resistance.
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| 7. |
- Sundin, Maria, 1965, et al.
(författare)
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Space sports – Sailing and equestrian sports in space
- 2019
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Ingår i: Communications in Computer and Information Science. - Cham : Springer International Publishing. - 1865-0937 .- 1865-0929. ; 975, s. 75-85
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Konferensbidrag (refereegranskat)abstract
- Sports in space? Is it at all possible to practice sports in our solar system but not on Planet Earth? Mars is our closest neighboring planet, and Titan is the largest moon of Saturn, and apart from the Earth it is the only body in our solar system where a liquid exists on the surface. Within the last ten years a system of lakes and rivers has been discovered. The climate and seasonal cycles of Titan are still not very well known, but the composition and pressure are fairly well established. Perhaps in the future boats will sail the lakes of Titan for research purposes or even sport. The purpose of this paper is to give an overview of the concept of space sports, looking at sailing on Titan and equestrian sports on Mars. For sailing, the conditions of Titan necessitate calculations of important parameters of sailing such as floatability, stability, hull resistance and sail forces. This paper shows that a sailing yacht on Titan will have twice as large displacement as on Earth and it will be 2.6 times less stable for the same beam. Since friction will be smaller, it will be faster than on Earth at low speed, but significantly slower at high speeds due to the wave generation. The same sail area is required to get the same sail forces if the average wind is 3 m/s, while a 9 times larger sail area is required if the wind speed is only 1 m/s. Equestrian sports on Mars could be a possibility, even if challenges exist in form of a cold climate and thin atmosphere with noxious gases. Due to the lower gravity sports such as show jumping, dressage and races would yield new records and new patterns of locomotion.
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| 8. |
- Allroth, Jens, 1984, et al.
(författare)
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Sailing Yacht Transom Sterns-a Systematic CFD Investigation
- 2015
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Ingår i: Proceedings, 5th High Performance Yacht Design Conference, Auckland, 8-11 March 2015. - 9781909024373 ; , s. 257-266
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Konferensbidrag (refereegranskat)abstract
- The question adressed in this project is whether modern hull lines with wide, box-shaped transoms, that seem to originate from extreme racing machines, are also beneficial for modern performance cruisers from a hydrodynamic performance point of view. A new 41 ft (12.3 m) hull was designed as an average of contemporary performance hulls in the 40 ft segment. The aft part of the hull was stretched stepwise and cut at constant length overall in order to systematically increase the transom size. Six hull variations with box shaped transoms were created in this way. To investigate the influence of the transom shape, the six hull variants were redesigned with a more rounded transom. The resistance was calculated for all twelve hulls in the upright and heeled conditions at Froude numbers 0.35 and 0.60. The computations were carried out using a Reynolds-Averaged Navier-Stokes (RANS) solver with a Volume of Fluid (VOF) representation of the free surface. The solver was validated against several hulls in the Delft Systematic Yacht Hull Series (DSYHS). Very different optima are found for the low and high speed cases. In an upwind-downwind race the round transoms performed best for the three fastest transom sizes. The fastest hull around the course has an immersed transom area to midship area ratio of 0.16 and it has a rounded shape. It is 1.9 % faster than a more box like transom. Overall the round transoms are faster around the race course.
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| 9. |
- Andersson, A, et al.
(författare)
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The Foiling Optimist
- 2017
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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
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Konferensbidrag (refereegranskat)
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| 10. |
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