| 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. |
- Alin, Niklas, 1963, et al.
(författare)
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Current Capabilities of DES and LES for Submarines at Straight Course
- 2010
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Ingår i: Journal of Ship Research. - 1542-0604 .- 0022-4502. ; 54:3, s. 184-196
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Tidskriftsartikel (refereegranskat)abstract
- The flow around an axisymmetric hull, with and without appendages, is investigated using large eddy simulation (LES), detached eddy simulation (DES), and Reynolds averaged Navier Stokes (RANS) models. The main objectives of the study is to investigate the effect of the different simulation methods and to demonstrate the feasibility of using DES and LES on relatively coarse grids for submarine flows, but also to discuss some generic features of submarine hydrodynamics. For this purpose the DARPA Suboff configurations AFF1 (bare hull) and AFF8 (fully appended model) are used. The AFF1 case is interesting because it is highly demanding, in particular for LES and DES, due to the long midship section on which the boundary layer is developed. The AFF8 case represents the complex flow around a fully appended submarine with sail and aft rudders. An actuator disc model is used to emulate some of the effects of the propulsor for one of the AFF8 cases studied. Results for the AFF8 model are thus presented for both “towed” and “self-propelled” conditions, whereas for the bare hull, only a “towed” condition is considered. For the AFF1 and the “towed” AFF8 cases experimental data are available for comparison, and the results from both configurations show that all methods give good results for first-order statistical moments although LES gives a better representation of structures and second-order statistical moments in the complex flow in the AFF8 case.
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| 3. |
- Alin, Niklas, 1963, et al.
(författare)
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Large Eddy Simulation of Junction Vortex Flows
- 2008
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Ingår i: 46th AIAA Aerospace Sciences Meeting and Exhibit; Reno, NV; United States; 7 January 2008 through 10 January 2008. - 9781563479373 ; , s. Art. no. 2008-0668
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this work is to learn more about the complex turbulent flow around a surface mounted slender object, commonly referred to as junction flows. This type of flows are common in many engineering applications such as turbine blade-hub assemblies, bridge support pillars, aircraft wing fuselage junctions, and submarine appendage-hull junctions, and is thus of great interest. In addition, we are interested in comparing how different Computational Fluid Dynamic (CFD) methods, such as Reynolds Averaged Navier Stokes (RANS), Detached Eddy Simulation (DES) and Large Eddy Simulation (LES) models manage to predict this flow when compared with experimental data. The flow physics is very complicated, with between two and six vortices interacting in the region between the upstream separation line and the body depending on the boundary layer and Re number. In addition, the flow is highly strained, anisotropic, and strongly affected by (unsteady) small-scale transport, and hence poses a great challenge to all CFD models of today. Here, we compare predictions from RANS, DES and LES with the experimental data of Pierce & Shin. RANS predicts somewhat too late separation, and a resulting horseshoe vortex system with extremely weak legs downstream of the body. In addition, RANS cannot provide information about the unsteadiness of the flow. DES typically predicts too early separation, resulting in a horseshow vortex located too far away from the body, but with horseshow vortex system that prevails throughout the computational domain. Wall modeled LES appears to capture the location of the separation well, and thus also the location of the horseshoe vortex system that prevails throughout the computational domain.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- 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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| 8. |
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| 9. |
- Feymark, Andreas, 1984, et al.
(författare)
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Large-Eddy Simulation of an Oscillating Cylinder in a Steady Flow
- 2013
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Ingår i: AIAA Journal. - 1533-385X .- 0001-1452. ; 51:4, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- In this work, large-eddy simulation is used to study the flow around a circular cylinder undergoing streamwise sinusoidal oscillations. This benchmark case is a first step toward studying engineering applications related to flow-induced vibrations. Both the flow physics, which correlate the flow development with the time varying loading of the cylinder at two different oscillation frequencies, as well as a validation of the fluid structure interaction methodology through comparison with experimental data for the same configuration are described. With the methodology used, large-eddy simulation based on a finite volume method capable of handling moving meshes gives force predictions that generally agree well with experimentally measured data, both with respect to the overall flow development as with force magnitude.
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| 10. |
- Feymark, Andreas, 1984, et al.
(författare)
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LES of the Flow Around an Oscillating Cylinder
- 2010
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Ingår i: 5th OpenFOAM Workshop.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the study is to provide understanding and give support in the validation of a fluid structure interaction methodology suitable for complex applications. The Computational Fluid Dynamics (CFD) method used is Large Eddy Simulation (LES) in which all the large scales of motions are resolved and only the effect of the small scales is modeled.
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| 11. |
- Feymark, Andreas, 1984, et al.
(författare)
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Numerical Simulation of an Oscillating Cylinder Using Large Eddy Simulation and Implicit Large Eddy Simulation
- 2012
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Ingår i: Journal of Fluids Engineering, Transactions of the ASME. - : ASME International. - 1528-901X .- 0098-2202. ; 134:3
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we use large eddy simulation (LES) to study the influence of grid and subgrid model on the lift and drag force predictions of a fixed cylinder undergoing streamwise sinusoidal oscillations in a steady flow, resulting in a varying Reynolds number, Re, within the range 405
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| 12. |
- Svennberg, U., et al.
(författare)
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Large eddy simulation of the flow past the DTMB5415 surface combatant hull with and without bilge keels
- 2011
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Ingår i: MARINE 2011 - Computational Methods in Marine Engineering IV (4th International Conference on Computational Methods in Marine Engineering, MARINE 2011; Lisbon; 28-30 September 2011). - 9788489925793 ; , s. 605-616
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Konferensbidrag (refereegranskat)abstract
- The flow around the DTMB5415 surface combatant hull with and without bilge keels is studied numerically by the use of a Large Eddy Simulation (LES) method. The main purpose for bilge keels is to reduce roll motions when operating in ocean waves. The flow resistance should at the same time be affected as little as possible. The computations presented here are for straight course in calm water conditions and show only a small change in the wake of the hull and there by a minimal effect on the resistance. The computations are made as a preparatory step before investigating other conditions, such as yaw angle.
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