| 1. |
- 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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| 2. |
- Korkmaz, Kadir Burak, 1989, et al.
(författare)
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A Validation Study of Full-Scale CFD Simulation for Sea Trial Performance Prediction of Ships
- 2023
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Ingår i: World Congress in Computational Mechanics and ECCOMAS Congress. - 2696-6999.
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Konferensbidrag (refereegranskat)abstract
- Shipping is a critical component of global trade but also accounts for a substantial portion of global greenhouse gas emissions. Recognising this issue, the International Maritime Organisation (IMO) has implemented new measures aimed at determining the energy efficiency of all ships and promoting continuous improvements, such as the Energy Efficiency Existing Ship Index (EEXI). As Computational Fluid Dynamics (CFD) can be used to calculate the EEXI value, RISE-SSPA1 and Flowtech have developed a CFD-based method for predicting full-scale ship performance with SHIPFLOW v7.0, which meets the new requirements of IMO. The method is validated through an extensive comparison study that examines the delivered power and propeller rotation rate between full-scale CFD predictions and high-quality sea trials using 14 common cargo ships of varying sizes and types. The comparison between the CFD predictions and 59 sea trials shows that both delivered power and RPM can be predicted with satisfactory accuracy, with an average comparison error of about 4% and 2%, respectively. The numerical methods used in this study differ significantly from the majority of the state-of-the-art CFD codes, highlighting their potential for future applications in ship performance prediction. Thorough validation with a large number of sea trials is essential to establish confidence in CFD-based ship performance prediction methods, which is crucial for the credibility of the EEXI framework and its potential to contribute to shipping decarbonisation.
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| 3. |
- Korkmaz, Kadir Burak, 1989, et al.
(författare)
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CFD PREDICTIONS INCLUDING VERIFICATION AND VALIDATION OF RESISTANCE, PROPULSION AND LOCAL FLOW FOR THE JAPAN BULK CARRIER (JBC) WITH AND WITHOUT AN ENERGY SAVING DEVICE
- 2015
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Ingår i: Proceedings, Tokyo 2015 Workshop on CFD in Ship Hydrodynamics. ; 3
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents the results of verification and validation (V&V) studies for resistance and self-propulsion simulations together with investigations of the local flow on the JAPAN Bulk Carrier (JBC) with and without an energy saving device (ESD). Computations are reported for all JBC test cases proposed by the Tokyo 2015 Workshop. In total, four V&V studies are presented for Case1.1a, Case1.2a, Case1.5a and Case1.6a using five systematically refined grids in each study. Local flow predictions for Case1.3a, Case1.4a, Case1.7a and Case1.8a are shown using the finest grids of the grid convergence studies. Resistance predictions using the finest grids are within 1% of the measured data both with and without the ESD. The predicted gain in delivered power is the same as in the measurements: 6.0%, although there is an under prediction of the effective wake in both cases
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| 4. |
- Larsson, Lars, 1945, et al.
(författare)
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Principi di Yacht Design (in Italian)
- 2022
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Principles of Yacht Design has established itself as the standard book on the subject for practising designers, naval architecture students, discerning boat owners as well as the boatbuilding industry as a whole. The fifth edition is completely revised and expanded. It examines every aspect of the process of yacht and powerboat design. The new edition includes new findings from recent research in aero and hydrodynamics, as well as covering the most recent changes to building standards. The authors have used a newly built 41-foot performance cruiser to demonstrate the practical application of yacht design theory. This new edition includes photos of the building process and detailed explanations.
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| 5. |
- Larsson, Lars, 1945, et al.
(författare)
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Principles of Yacht Design (4th ed.)
- 2013
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- The first edition of the Principles of Yacht Design was published in 1994. Since then there have been two new editions, and the book has been translated into German, Japanese and Korean. A special edition is published in the United States. The book has thus been very well received, and in this fourth edition we have kept the structure and the main contents of the previous editions. The basic idea is to cover all aspects of yacht design, from the specification, through the hydro- and aerodynamic design, structural assessment and layout, to the final evaluation. Emphasis is placed on concept descriptions, but formulae, separated from the text, are included in sufficient depth for a complete design of a new yacht. An important feature of the book is the example yacht, used throughout the book to exemplify the use of the formulae. This is where the present edition differs most from the previous ones. A completely new modern performance cruiser, the YD–41 has replaced the original YD-40, designed for the first edition. This has called for a revision of most of the figures and important parts of the text. In connection with the new design, the statistics found in the design chapters have been completely revised, and are now based on yachts designed during the past ten years. The primary designer of the new yacht is Michal Orych, who is now welcomed as the third author of the book.Since the first edition there have been regular updates particularly in two areas: hydrodynamic formulas based on the Delft systematic yacht hull series (DSYHS), and ISO standards for the safety and structural integrity of sailing yachts. The authors are indebted to Dr Lex Keuning, the manager of DSHYS, for his advice in this matter. The ISO 12217-2 seaworthiness standard was developed under the chairmanship of Andrew Blyth, and the ISO scantlings standard 12215 under the late Fritz Hartz and more recently Gregoire Dolto. Thanks are due to all of them for their support, and for their permission to use unpublished parts of the standards. In the present edition, new resistance formulae are presented from DSHYS, and the ISO 12215 standard has been updated with respect to rudders and appendages.Since the first edition there has been a dramatic development in Computational Fluid Dynamics (CFD), and this is reflected in the present edition, where a considerably expanded section in the last chapter is devoted to this exciting technique.
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| 9. |
- Ljungqvist, Kasper, 1984, et al.
(författare)
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Comparison of Modern Keel Types for Sailing Yachts
- 2018
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Ingår i: Transactions of the Royal Institution of Naval Architects Part B: InternationalJournal of Small Craft Technology. - 1740-0694. ; 159, s. 81-
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Tidskriftsartikel (refereegranskat)abstract
- The performance of three bulb keels is compared with that of a traditional fin keel. Hydrodynamic data from wind tunnel tests are used in a velocity prediction program (VPP) with the keels fitted to a 40’ cruising yacht. Two scenarios are investigated: keel retrofitting and new design. In retrofitting, the sail, mast and rig are unchanged, while in new design they are varied to obtain a constant heel angle (Dellenbaugh). Three keel materials are considered: cast iron, lead or a mix thereof. As expected, the bulb keels are superior to the fin keel in all but the lightest winds in the retrofit scenario. The differences between the bulb keels are small, but the keel with a bulb integrated with the fin is slightly slower than the keels with more distinct bulbs, in either L- or T-configuration. These are very close in retrofit, but the T-configuration has a slight advantage in the new design scenario.
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| 10. |
- Ljungqvist, Kasper, 1984, et al.
(författare)
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Investigation of Keel Bulbs for Sailing Yachts
- 2012
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Ingår i: Proceedings, 4th High Performance Yacht Design Conference, Auckland, 12-15 March, 2012.
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Konferensbidrag (refereegranskat)abstract
- An experimental investigation of four sailboat keels is presented. Three of the keels have bulbs of different shapes: an L-keel, a T-keel and an integrated bulb keel. These shapes are found on most sailing yachts designed during the past twenty years. The fourth keel is a standard fin keel. Lift and drag of the four keels have been measured in a wind tunnel and the results are compared. To obtain more practical results the measured data have been input into a VPP, and the performance of a 40 foot yacht equipped with the different keels is evaluated. Although the performance differences are not great, they are clearly of interest in yacht racing. Since one purpose of the experimental campaign was to develop a data base for CFD validation, emphasis is placed on uncertainty estimation. A numerical optimisation of the most common bulb, the integrated one, is also reported. A CFD code was linked to an optimiser and a CAD program, and the drag to lift ratio of the keel was minimized at an angle of attack of 4°. The optimisation was preceded by a CFD code validation for the keel. It is shown in the paper that the proposed technique improves the performance such that the worst keel becomes competitive with the best non-optimised one.
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