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- Andersson, Jennie, 1986, et al.
(author)
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Ship-scale CFD benchmark study of a pre-swirl duct on KVLCC2
- 2022
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In: Applied Ocean Research. - : Elsevier Ltd. - 0141-1187 .- 1879-1549. ; 123
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Journal article (peer-reviewed)abstract
- Installing an energy saving device such as a pre-swirl duct (PSD) is a major investment for a ship owner and prior to an order a reliable prediction of the energy savings is required. Currently there is no standard for how such a prediction is to be carried out, possible alternatives are both model-scale tests in towing tanks with associated scaling procedures, as well as methods based on computational fluid dynamics (CFD). This paper summarizes a CFD benchmark study comparing industrial state-of-the-art ship-scale CFD predictions of the power reduction through installation of a PSD, where the objective was to both obtain an indication on the reliability in this kind of prediction and to gain insight into how the computational procedure affects the results. It is a blind study, the KVLCC2, which the PSD is mounted on, has never been built and hence there is no ship-scale data available. The 10 participants conducted in total 22 different predictions of the power reduction with respect to a baseline case without PSD. The predicted power reductions are both positive and negative, on average 0.4%, with a standard deviation of 1.6%-units, when not considering two predictions based on model-scale CFD and two outliers associated with large uncertainties in the results. Among the variations present in computational procedure, two were found to significantly influence the predictions. First, a geometrically resolved propeller model applying sliding mesh interfaces is in average predicting a higher power reduction with the PSD compared to simplified propeller models. The second factor with notable influence on the power reduction prediction is the wake field prediction, which, besides numerical configuration, is affected by how hull roughness is considered. © 2022 The Authors
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| 2. |
- Hino, Takanori, et al.
(author)
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Introduction, conclusions and recommendations
- 2021
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In: Lecture Notes in Applied and Computational Mechanics. - Cham : Springer International Publishing. - 1860-0816 .- 1613-7736. ; 94, s. 1-21
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Book chapter (other academic/artistic)abstract
- The Tokyo 2015 Workshop on CFD in Hydrodynamics was the seventh in a series started in 1980. The purpose of the Workshops is to regularly assess the state of the art in Numerical Hydrodynamics and to provide guidelines for further developments in the area. The 2015 Workshop offered 16 test cases for three ship hulls. A total of 36 participating groups of CFD specialists submitted their computed results during the fall of 2015. The results were compiled by the organizers and discussed at a meeting in Tokyo in December 2015. In this chapter the background and development of the Workshops since the start are presented. The three hulls used in the 2015 Workshop are introduced and the computations requested from the participants are specified. Based on a questionnaire sent to all participants the details of their CFD methods are listed, and finally the general conclusions from each chapter and recommendations for future Workshops are presented. The detailed results of the computations are discussed in subsequent Chapters.
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| 3. |
- Korkmaz, Kadir Burak, et al.
(author)
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CFD based form factor determination method
- 2021
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In: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 220
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Journal article (peer-reviewed)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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| 4. |
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| 5. |
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Numerical Ship Hydrodynamics - An Assessment of the Tokyo 2015 Workshop
- 2021
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Editorial collection (peer-reviewed)abstract
- Since 1980, Workshops on CFD in Ship Hydrodynamics have been held regularly. The main purpose of these Workshops is to assess the state-of-the-art in CFD for hydrodynamic applications. Active researchers in the field worldwide are invited to provide computed results for a number of well specified test cases, and the organizers collect and present the results such that comparisons between different methods can be made easily. Detailed information about each method is also reported via a questionnaire provided by the organizers. All results are discussed at a meeting, and a final assessment of the workshop is made by the organizers. The Tokyo 2015 Workshop attracted 36 groups from all over the world, and different types of computations were carried out for three hulls. It was the largest of the workshops in the series so far. All computed results were compiled in a volume, called Proceedings II, and distributed at the meeting, which was held in Tokyo in December 2015. The volume also includes short papers describing the computational methods and the results in more detail. In the present book, in-depth evaluations of all computed results are presented. For some of the test cases additional computations by the organizers are presented on topics of particular interest found at the meeting. All experimental data are reported, as well as a comprehensive set of new data obtained after the workshop. The book has been written by the organizers and their co-workers. Supplementary materials are available for free at http://www.springer.com/gp/book/9783030475710. The book constitutes the final documentation of the Tokyo 2015 Workshop and gives a state-of-the-art assessment of the CFD capabilities within the area of Ship Hydrodynamics.
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