| 1. |
- Alin, Niklas, 1963, et al.
(författare)
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3D Unsteady Computations for Submarine-Like Bodies
- 2005
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Ingår i: 43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, Jan. 10-13, 2005. ; , s. 353-369
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Konferensbidrag (refereegranskat)abstract
- Results from a computational study using Unsteady Reynolds Averaged Navier Stokes (URANS) models and Large Eddy Simulation (LES) of flows past submarine-like bodies are here presented. The aims are to evaluate URANS and LES for high-Re number hydrodynamic flows, to investigate the influence of the turbulence and subgrid turbulence modeling, and to discuss some features of submarine hydrodynamics. For this purpose we have chosen to examine the flow past a prolate spheroid at 10° and 20° angle of attack at a body length Re number of 4-106, and the flow past the DARPA-2 Suboff bare hull and fully appended hull configurations at a body length Re number of 12-106. For both cases experimental data is available for comparison. One finite element and one finite volume flow solver has been used - both with the capability of employing a range of turbulence models and with the capacity of using unstructured and hybrid grids. Better agreement between predictions and experimental data is obtained with LES than with the URANS models, but at a considerably higher price, due to the finer grids and finer temporal resolution in LES.
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| 2. |
- Andersen, Casper W., et al.
(författare)
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OPTIMADE, an API for exchanging materials data
- 2021
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Ingår i: Scientific Data. - : Nature Portfolio. - 2052-4463. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The Open Databases Integration for Materials Design (OPTIMADE) consortium has designed a universal application programming interface (API) to make materials databases accessible and interoperable. We outline the first stable release of the specification, v1.0, which is already supported by many leading databases and several software packages. We illustrate the advantages of the OPTIMADE API through worked examples on each of the public materials databases that support the full API specification.
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| 3. |
- Andersson, Evert, et al.
(författare)
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On the Optimization of a Track-Friendly Bogie for High Speed
- 2009
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Ingår i: 21st International Symposium on Dynamics of Vehicles on Roads and Tracks, IAVSD'09, Stockholm, August 17-21, 2009..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- When designing and optimizing a rail vehicle there is a contradiction between, on the one hand, stability on straight track at high speed and, on the other hand, reasonable wheel and rail wear in small- and medium radius curves. Higher speeds require to some extent stiffer wheelset guidance to avoid hunting and ensure stability. However, with stiffer wheelset guidance the risk of increased wheel and rail wear in curves is imminent. In this paper, the process of developing and optimizing a track-friendly bogie is described. A multi-body system (MBS) simulation model was used, taking due consideration to nonlinearities in suspension and wheel-rail contact, as well as realistic flexibilities in the track. Adequate and systematic consideration is taken to a wide range of possible non-linear wheel-rail combinations. Dynamic stability is investigated both on straight track and in wide curves at high speeds. The balance between flange wear and tread wear is studied in order to maximize wheel life between re-profiling operations in the intended average operation. The result is a bogie with relatively soft wheelset guidance allowing passive radial self-steering, which in combination with appropriate yaw damping ensures stability on straight track at higher speeds. The bogie has been subject to both certification testing and long-term service testing in the Gröna Tåget (the Green Train) research and development programme.
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| 4. |
- Andersson, Evert, et al.
(författare)
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Radial Self-Steering Bogies : Recent Developments for High Speed
- 2009
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Ingår i: 7th International Conference on Railway Bogies and Running Gears. - 9789634209775 ; , s. 63-72
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Considering the total cost of railway operations, it is important to reduce the deterioration caused to the track by rail vehicles and vice versa. Radial steering running gear, where the wheelsets take up approximate radial positions in curves, is an important mean of reducing rail and wheel wear. They also allow curves to be negotiated at higher lateral acceleration on non-perfect track, without exceeding stipulated limits for lateral track shift forces. In order to run dynamically stable at high speed, the damping of the bogie must be appropriate, in particular the yaw damping between bogies and carbody. Radial self-steering bogies are used on more than 1200 rail passenger vehicles in Scandinavia since the early 1980’s. The maximum service speed of these vehicles ranges up to 210 km/h. Ongoing development seems to confirm that the use of such bogies can be extended into the very high-speed area of at least 250 km/h. There has previously been some scepticism on the feasibility of soft wheelset guidance for higher speeds, in particular with respect to running stability. Although there are some limitations in the performance of radial self-steering bogies, this solution is robust and well-proven since about 25 years. The ultimate future may be a mechatronic bogie, where the wheelsets are guided in the most optimal way through controlled and forced radial steering. Such bogies may be justified if performance is out of the possible range of passive self-steering solutions.
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| 5. |
- Andersson, Evert, et al.
(författare)
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Radial self-steering bogies - Development, advantages and limitations
- 2007
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Ingår i: ZE Vrail - Glasers Annalen: Zeitschrift fuer das gesamte System Bahn. - 1618-8330. ; 131:Suppl., s. 248-259
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Tidskriftsartikel (refereegranskat)abstract
- Considering the total cost of railway operations, It is important to reduce the deterioration caused to the track by rail vehicles and vice versa. Radial steering running gear, where the wheelsets take up approximate radial positions in curves, is an important mean of reducing rail and wheel wear. They also allow curves to be negotiated at higher lateral acceleration on non-perfect track, without exceeding stipulated limits for lateral track shift forces. In order to run dynamically stable at high speed, the damping of the bogie must be appropriate, in particular the yaw damping between bogies and car body. Since the mid-1970's radial self-steering bogles have been developed and used in about 1 200 passenger rail vehicles in Scandinavia. This development continues and during 2006 a test train with radial self-steering bogies is run in speeds up till 281 km/h as part of the Swedish R&D program "GrönaTå get" (GreenTrain). Although there are limitations in the performance of passively self-steering bogles they are a simple and proven solution. Ultimately, In the future actively controlled radial steering may be considered asan appropriate mean to achieve higher performance and track-friendliness.
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| 6. |
- Arvidsson, Rickard, 1984, et al.
(författare)
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Life cycle assessment of Biodiesel - Hydrotreated oil from rape, oil palm or Jatropha
- 2008
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Ingår i: Annual Poster Exhibition at the Department of Chemical and Biological Engineering, Chalmers University of Technology, Mars 6th, 2008, Göteborg, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is a need for fuels based on renewable resources that have acceptable emission profiles and that are functional for truck engines used in heavy vehicles. Volvo has participated in the CONCAWE/EUCAR/JRC WTW study, which analyzed a number of candidate fuels, several process routes to produce each fuel as well as different raw material choices. However, the CONCAWE study did not include any second generation hydrogenated vegetable oil type biodiesel. In the present study, Volvo and Chalmers investigate and benchmark hydrogenated vegetable oils. Different production routes from different proposed raw materials are investigated using life cycle assessment modeling. Raw materials considered are oil from rape seed (grown in Germany), palm oil (grown in Malaysia) and oil from the fruits of Jatropha curcas (grown in India). The raw material is converted into hydrogenated oil at a production site in northern Europe and used at the European market. Results regarding life cycle global warming potential and energy use are presented.
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| 7. |
- Arvidsson, Rickard, 1984, et al.
(författare)
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Life cycle assessment of hydrotreated vegetable oil from rape, oil palm and Jatropha
- 2011
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526 .- 1879-1786. ; 19:2-3, s. 128-137
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Tidskriftsartikel (refereegranskat)abstract
- A life cycle assessment of hydrotreated vegetable oil (HVO) biofuel was performed. The study wascommissioned by Volvo Technology Corporation and Volvo Penta Corporation as part of an effort to gaina better understanding of the environmental impact of potential future biobased liquid fuels for cars andtrucks. The life cycle includes production of vegetable oil from rape, oil palm or Jatropha, transport of theoil to the production site, production of the HVO from the oil, and combustion of the HVO. The functionalunit of the study is 1 kWh energy out from the engine of a heavy-duty truck and the environmentalimpact categories that are considered are global warming potential (GWP), acidification potential (AP),eutrophication potential (EP) and embedded fossil production energy. System expansion was used totake into account byproducts from activities in the systems; this choice was made partly to make thisstudy comparable to results reported by other studies. The results show that HVO produced from palmoil combined with energy production from biogas produced from the palm oil mill effluent has thelowest environmental impact of the feedstocks investigated in this report. HVO has a significantly lowerlife cycle GWP than conventional diesel oil for all feedstocks investigated, and a GWP that is comparableto results for e.g. rape methyl ester reported in the literature. The results show that emissions from soilcaused by microbial activities and leakage are the largest contributors to most environmental impactcategories, which is supported also by other studies. Nitrous oxide emissions from soil account for morethan half of the GWP of HVO. Nitrogen oxides and ammonia emissions from soil cause almost all of thelife cycle EP of HVO and contribute significantly to the AP as well. The embedded fossil production energywas shown to be similar to results for e.g. rape methyl ester from other studies. A sensitivity analysisshows that variations in crop yield and in nitrous oxide emissions from microbial activities in soil cancause significant changes to the results.
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| 10. |
- Bensow, Rickard, 1972, et al.
(författare)
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Large Eddy Simulations for Marine Flows
- 2007
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Ingår i: STG-Lectureday "CFD in Ship Design", Hamburg, Germany.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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