| 1. |
- Lejon, Marcus, 1986, et al.
(författare)
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Multidisciplinary Design of a Three Stage High Speed Booster
- 2017
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Ingår i: ASME Turbo Expo 2017: Turbine Technical Conference and Exposition. - : ASME Press. ; 2B-2017
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Konferensbidrag (refereegranskat)abstract
- The paper describes a multidisciplinary conceptual design of an axial compressor, targeting a three stage, high speed, high efficiency booster with a design pressure ratio of 2.8. The paper is outlined in a step wise manner starting from basic aircraft and engine thrust requirements, establishing the definition of the high speed booster interface points and its location in the engine. Thereafter, the aerodynamic 1D/2D design is carried out using the commercial throughflow tool SC90C. A number of design aspects are described, and the steps necessary to arrive at the final design are outlined. The SC90C based design is then carried over to a CFD based conceptual design tool AxCent, in which a first profiling is carried out based on a multiple circular arc blade definition. The design obtained at this point is referred to as the VINK compressor. The first stage of the compressor is then optimized using an in-house optimization tool, where the objective functions are evaluated from detailed CFD calculations. The design is improved in terms of efficiency and in terms of meeting the design criteria put on the stage in the earlier design phases. Finally, some aeromechanical design aspects of the first stage are considered. The geometry and inlet boundary conditions of the compressor are shared with the turbomachinery community on a public server. This is intended to be used as a test case for further optimization and analysis.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Liefvendahl, Mattias, 1971, et al.
(författare)
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Wall-Modeled LES for Ship Hydrodynamics in Model Scale
- 2021
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Ingår i: Journal of Ship Research. - : Society of Naval Architects and Marine Engineers. - 1542-0604 .- 0022-4502. ; 65:1, s. 41-54
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Tidskriftsartikel (refereegranskat)abstract
- A complete approach for wall-modeled large-eddy simulation (WMLES) is demonstrated for the simulation of the flow around a bulk carrier in the model scale. Essential components of the method are an a-priori estimate of the thickness of the turbulent boundary layer (TBL) over the hull and to use an unstructured grid with the appropriate resolution relative to this thickness. Expressions from the literature for the scaling of the computational cost, in terms of the grid size, with Reynolds number, are adapted in this application. It is shown that WMLES is possible for model scale ship hydrodynamics, with similar to 10(8) grid cells, which is a gain of at least one order of magnitude as compared with wall-resolving LES. For the canonical case of a flat-plate TBL, the effects of wall model parameters and grid cell topology on the predictive accuracy of the method are investigated. For the flat-plate case, WMLES results are compared with results from direct numerical simulation, RANS (Reynolds-averaged Navier-Stokes), and semi-empirical formulas. For the bulk carrier flow, WMLES and RANS are compared, but further validation is needed to assess the predictive accuracy of the approach.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Stadler, Michael, et al.
(författare)
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A Customised Finn Dinghy Rudder for Optimal Olympic Performance
- 2020
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Ingår i: Proceedings (MDPI). - Basel Switzerland : MDPI. - 2504-3900. ; 49:1
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Konferensbidrag (refereegranskat)abstract
- Because of the long history of the Finn Dinghy sailing class, the difference between a gold medal and a mediocre result often comes down to personal mistakes of the sailor, or to who has the most optimised equipment. Regarding the latter, the Finn class rules permit certain design variations of the hull, mast, sail and rudder. In the current contribution, we describe a method for developing a customised rudder system aimed at optimal performance during the Tokyo 2020 Olympics. Based on hydrodynamic analysis of existing rudder designs, an improved rudder geometry was developed. Based on the concept geometry, the rudder and tiller were structurally designed and manufactured to achieve high stiffness and sufficient strength, while respecting the minimum mass requirements as specified by the rules.
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| 8. |
- Korkmaz, Kadir Burak, et al.
(författare)
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CFD based form factor determination method
- 2021
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 220
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Tidskriftsartikel (refereegranskat)abstract
- The 1978 ITTC Power Prediction method is used to predict the propulsive power of ships through towing tank testing. The form factor approach and its determination in this method have been questioned. This paper investigates the possibility to improve the power predictions by introducing Combined CFD/EFD Method where the experimental determination of form factor is replaced by double body RANS computations applied for open cases KVLCC2 and KCS, including first-time published towing tank tests of KVLCC2 at ballast condition including an experimental uncertainty analysis specifically derived for the form factor. Computations from nine organisations and seven CFD codes are compared to the experiments. The form factor predictions for both hulls in design loading condition compared well with the experimental results in general. For the KVLCC2 ballast condition, majority of the form factors were under-predicted while staying within the experimental uncertainty. Speed dependency is observed with the application of ITTC57 line but it is reduced with the Katsui line and nearly eliminated by numerical friction lines. Comparison of the full-scale viscous resistance predictions obtained by the extrapolations from model scale and direct full-scale computations show that the Combined CFD/EFD Method show significantly less scatter and may thus be a preferred approach.
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| 9. |
- Alexandersson, Martin, et al.
(författare)
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Prediction of roll motion using fully nonlinear potential flow and ikeda’s method
- 2021
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Ingår i: Proceedings of the International Offshore and Polar Engineering Conference. - : International Society of Offshore and Polar Engineers. - 1098-6189 .- 1555-1792. - 9781880653821 ; , s. 1670-1679
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Konferensbidrag (refereegranskat)abstract
- Getting the best possible accuracy with the lowest possible computational cost is an important factor in the early design stage of ships. Potential flow-based analysis presents such a solution for seakeeping analyses. The accuracy of roll motion in potential flow is however not so good, due to the large influence from vicsous roll damping, which is missing in these calculations. This paper proposes a hybrid method, as a solution to this problem, where the viscous roll damping from Ikeda’s semi-empirical method is injected into an existing 3D unsteady fully nonlinear potential flow (FNPF) method. The hybrid method is investigated using roll decay tests with the KVLCC2 test case. This investigation shows that the accuracy of simulated roll motions is significantly improved and also shows good agreement with the corresponding roll decay model tests.
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| 10. |
- Olsson, Robin, 1958, et al.
(författare)
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Design, Manufacture, and Cryogenic Testing of a Linerless Composite Tank for Liquid Hydrogen
- 2024
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Ingår i: Applied Composite Materials. - : Springer Nature. - 1573-4897 .- 0929-189X. ; 31:4, s. 1131-1154
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes design, manufacture, and testing of a linerless composite vessel for liquid hydrogen, having 0.3 m diameter and 0.9 m length. The vessel consists of a composite cylinder manufactured by wet filament winding of thin-ply composite bands, bonded to titanium end caps produced by additive manufacturing. The aim was to demonstrate the linerless design concept with a thin-ply composite for the cylinder. The investigation is limited to the internal pressure vessel, while real cryogenic tanks also involve an outer vessel containing vacuum for thermal insulation. Thermal stresses dominate during normal operation (4 bar) and the layup was selected for equal hoop strains in the composite cylinder and end caps during filling with liquid hydrogen. Two vessels were tested in 20 cycles, by filling and emptying with liquid nitrogen to 4 bar, without signs of damage or leakage. Subsequently, one vessel was tested until burst at almost 30 bar.
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