| 1. |
- Boelens, O. J., et al.
(författare)
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F-16XL Geometry and Computational Grids Used in Cranked-Arrow Wing Aerodynamics Project International
- 2009
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Ingår i: Journal of Aircraft. - : American Institute of Aeronautics and Astronautics (AIAA). - 0021-8669 .- 1533-3868. ; 46:2, s. 369-376
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the Cranked-Arrow Wing Aerodynamics Project International was to allow a comprehensive validation of computational fluid dynamics methods against the Cranked-Arrow Wing Aerodynamics Project flight database. A major part of this work involved the generation of high-quality computational grids. Before the grid generation, an airtight geometry of the F-16XL, aircraft was generated by a cooperation of the Cranked-Arrow Wing Aerodynamics Project International partners. Based on this geometry description, both structured and unstructured grids have been generated. The baseline structured (multiblock) grid (and a family of derived grids) has been generated by the National Aerospace Laboratory. Although the algorithms used by the National Aerospace Laboratory had become available just before the Cranked-Arrow Wing Aerodynamics Project International and thus only a limited experience with their application to such a complex configuration had been gained, a grid of good quality was generated well within four weeks. This time compared favorably with that required to produce the unstructured grids in the Cranked-Arrow Wing Aerodynamics Project International. The baseline all-tetrahedral and hybrid unstructured grids have been generated at NASA Langley Research Center and the U.S. Air Force Academy, respectively. To provide more geometrical resolution, trimmed unstructured grids have been generated at the European Aeronautic Defence and Space Company's Military Air Systems, University of Tennessee at Chattanooga SimCenter, Boeing Phantom Works, Royal Institute of Technology, and the Swedish Defence Research Agency. All grids generated within the framework of the Cranked-Arrow Wing Aerodynamics Project International will be discussed in the paper. Both results obtained on the structured grids and the unstructured grids showed a significant improvement in agreement with flight-test data in comparison with those obtained on the structured multiblock grid used during the Cranked-Arrow Wing Aerodynamics Project.
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| 2. |
- Görtz, Stefan, et al.
(författare)
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Numerical Solutions for the Cawapi Configuration on Unstructured Grids at KTH/FOI, Sweden : Part I
- 2009
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Ingår i: Understanding and Modeling Vortical Flows to Improve the Technology Readiness Level for Military Aircraft.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Steady and unsteady viscous simulations of a full-scale, semi-span and full-span model of the F-16XL-1 aircraft at seven different flight Reynolds/Mach number combinations have been performed with an unstructured CFD code. The steady-state simulations are with several turbulence models of different complexity. Detached-Eddy Simulation (DES) has been used to compute the unsteady flow. The computed results are compared with public domain flight-test data. Very good agreement is demonstrated for surface pressure distribution, local skin friction and boundary velocity profiles. The different turbulence models performed almost equally well, except the Spalart-Allmaras model, which failed to predict the flow qualitatively and quantitatively. The Differential Reynolds Stress Model (DRSM) outperformed all other models when it comes to local span-wise skin friction. DES was superior over RANS modeling at the highest angle of attack, where the flow over the outer wing is separated and partly unsteady.
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| 3. |
- Görtz, Stefan, et al.
(författare)
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Standard Unstructured Grid Solutions for Cranked Arrow Wing Aerodynamics Project International F-16XL
- 2009
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Ingår i: Journal of Aircraft. - : American Institute of Aeronautics and Astronautics (AIAA). - 0021-8669 .- 1533-3868. ; 46:2, s. 385-408
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Tidskriftsartikel (refereegranskat)abstract
- Steady and unsteady viscous flow simulations of a full-scale, semispan, and full-span model of the F-16XL-1 aircraft are performed with three different computational fluid dynamics codes using a common unstructured grid. Six different flight conditions are considered. They represent Reynolds and Mach number combinations at subsonic speeds, with and without sideslip. The steady computations of the flow at these flight conditions are made with several Reynolds-averaged Navier-Stokes turbulence models of different complexity. Detached-eddy simulation, delayed detached-eddy simulation, and an algebraic hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation model are used to quantify unsteady effects at the same flight conditions. The computed results are compared with flight-test data in the form of surface pressures, skin friction, and boundary-layer velocity profiles. The focus of the comparison is on turbulence modeling effects and effects of unsteadiness. The overall agreement with flight data is good, with no clear trend as to which physical modeling approach is superior for this class of flow. The Reynolds-averaged Navier-Stokes turbulence models perform well in predicting the flow in an average sense. However, some of the flow conditions involve locally unsteady flow over the aircraft, which are held responsible for the scatter between the different turbulence modeling approaches. The detached-eddy simulations are able to quantify the unsteady effects, although they are not consistently better than the Reynolds-averaged Navier-Stokes turbulence models in predicting the flow in an average sense in these flow regions. Detached-eddy simulation fails to predict boundary-layer profiles consistently over a range of flow regimes, with delayed detached-eddy simulation and hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation models offering a remedy to recover some of the predictive capabilities of the underlying Reynolds-averaged Navier-Stokes turbulence model. Nonetheless, the confidence in the predictive capabilities of the computational fluid dynamics codes with regard to complex vortical flowfields around high-performance aircraft of this planform increased significantly during this study.
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