| 1. |
- Frink, N. T., et al.
(författare)
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Collaborative study of incipient separation on 53°-swept diamond wing
- 2016
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Ingår i: Aerospace Science and Technology. - : Elsevier. - 1270-9638 .- 1626-3219. ; 57, s. 76-89
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Tidskriftsartikel (refereegranskat)abstract
- A systematic analysis of incipient separation and subsequent vortex formation from moderately-swept blunt leading edges is presented for a 53°-swept diamond wing. This work contributes to a collective body of knowledge generated within the multinational NATO/STO AVT-183 Task Group titled "Reliable Prediction of Separated Flow Onset and Progression for Air and Sea Vehicles". Details of vortex formation are inferred from numerical solutions of two flow solvers after establishing a good correlation of the global flow field and surface pressure distributions with those from wind tunnel measurements. From this, significant and sometimes surprising insights into the nature of incipient separation and part-span vortex formation are derived from the wealth of information available in the computational solutions.
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| 2. |
- Luckring, James M., et al.
(författare)
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Synthesis of Hybrid Computational Fluid Dynamics Results for F-16XL Aircraft Aerodynamics
- 2017
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Ingår i: Journal of Aircraft. - 0021-8669 .- 1533-3868. ; 54:6, s. 2100-2114
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Tidskriftsartikel (refereegranskat)abstract
- A synthesis is presented of recent numerical predictions for the F-16XL aircraft flowfields and aerodynamics. The computational analyses were all performed with hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation formulations, with an emphasis on unsteady flows and associated aerodynamics, and results from five computational methods are included. The work focused on one particular low-speed high angle-of-attack flight-test condition, and comparisons against flight-test data are included. This work represents the third coordinated effort using the F-16XL aircraft, and a unique flight-test dataset, to advance the knowledge of slender airframe aerodynamics as well as the capability for predicting these aerodynamics with advanced computational fluid dynamics formulations. The prior efforts were identified as the Cranked-Arrow Wing Aerodynamics Project International.
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| 3. |
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| 4. |
- Tomac, Maximillian, et al.
(författare)
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Calibration and verification of a γ - Reθt transition prediction method for airfoil computations
- 2013
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Ingår i: 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013. - 9781624101816
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the implementation and verification of a γ - Reθt correlation based transition prediction method previously presented by Langtry et al. The two additional transport equations used for predicting transition and a novel set of equations for the production terms are implemented into the Computational Fluid Dynamics code Edge. The model predicts two-dimensional transition phenomena such as transition due to Tollmein-Schlichting instabilities, bypass transition and separation induced transition. The transition prediction model is calibrated to the well-known Ercoftac wind tunnel tests using an optimization program based on a direct search method available in Matlab. The model is tested with several non-calibrated cases comparable with industry standard airfoils (low speed, transonic) and wind tunnel experiments as well as the MSES code that uses a en method. The main part of this work was performed as part of the research project Aerodynamic Loads Estimation at Extremes of the Flight Envelope (ALEF) (Grant Agreement no: 211785), 7th EU framework program.
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| 5. |
- Tomac, Maximillian, et al.
(författare)
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Computational Fluid Dynamics Predictions of Control-Surface Effects for F-16XL Aircraft
- 2017
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Ingår i: Journal of Aircraft. - : AMER INST AERONAUTICS ASTRONAUTICS. - 0021-8669 .- 1533-3868. ; 54:2, s. 395-408
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Tidskriftsartikel (refereegranskat)abstract
- Computational fluid dynamics methods play an increasingly important role in aircraft design and development. Some examples are conditions that cannot be tested before a flight test. To rely on these methods, it is essential that they are assessed and evaluated with a state-of-the-art wind tunnel test and/or in-flight data. In a previous project, Cranked-Arrow Wing Aerodynamics Project International, it was reported that all computational fluid dynamics methods failed to some degree in the transonic regime where shock-vortex interaction phenomena were present. Detailed analysis of surface pressure distribution showed that computational fluid dynamics was not able replicate the correct flowfield and produce acceptable results. This paper aims to restudy those transonic flight conditions for which computational fluid dynamics underperforms and to try to determine or shed light on the extent to which surface effects contribute to the computational fluid dynamics predictions.
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| 6. |
- Tomac, Maximillian, et al.
(författare)
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Engineering methods applied to an unmanned combat air vehicle configuration
- 2012
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Ingår i: Journal of Aircraft. - 0021-8669 .- 1533-3868. ; 49:6, s. 1610-1618
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Tidskriftsartikel (refereegranskat)abstract
- Engineering methods provide fast and economic predictions of the aerodynamic characteristics of complex flight vehicles. This paper investigates the application of three specific engineering methods to a unmanned combat air vehicle (UCAV) configuration, termed the Stability and Control Configuration (SACCON), that is still under investigation and that is the subject of an intensive computational and experimental study by the NATO Research and Technology Organization task group AVT-161 for better understanding of its stability and control characteristics. Computational fluid dynamics (CFD) data are computed for theSACCONat wind-tunnel conditions and are compared and evaluated against the measured values, especially in terms of their implications for low-speed longitudinal flight characteristics. Because of their reduced-order modeling compared with Reynolds-averaged Navier-Stokes CFD, predictions by the engineering methods are restricted to the flight-condition range governed by linear flow physics, which, for the SACCON in low speed is 0 α 10 deg. Despite the limited range in angle of attack, it was discovered that, due to the large sweep angle of theSACCONwing and its tip section of zero taper ratio, peak suction levels at the tip were so high that the boundary layer separated there instead. This viscous effect caused a discrepancy between the predicted and measured values of the pitching moment. The remedy taken was to increase the washout for theSACCONwing by modifying its twist and camber, and predictions made for this shape confirmed that linear flow physics prevailed then and that the static stability margin was increased. Furthermore, a series of predictions were made at high speed to establish the drag-divergence Mach numberMdd. The investigations carried out here demonstrate the continued usefulness of engineering methods not only as an analysis tool during the initial aircraft design phase but also as a design tool to improve the shape definition of the vehicle to achieve better performance.
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| 7. |
- Tomac, Maximillian, et al.
(författare)
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Towards automated hybrid-prismatic mesh generation
- 2014
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Ingår i: Procedia Engineering. - : Elsevier BV. - 1877-7058. ; , s. 377-389
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Konferensbidrag (refereegranskat)abstract
- An open-source implementation of an efficient mesh generation procedure for hybrid prismatic-tetrahedral meshes intended for use in Reynolds-averaged Navier-Stokes solutions is presented. The method employed combines the established, and very fast, Delaunay-based tetrahedral mesh generator TetGen with a novel technique for the creation of a prismatic layer. Satisfactory mesh quality is demonstrated by comparing solutions obtained using the new meshes with reference data computed on advancing-front grids. Mesh generation time is shown to be substantially less than with some other methods. Overall, the presented implementation is deemed a valuable tool for cases where many meshes need to be generated for routine analyses and turnaround time is critical.
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| 8. |
- Zhang, Mengmeng, et al.
(författare)
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Variable fidelity methods and surrogate modeling of critical loads on X-31 aircraft
- 2013
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Ingår i: 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781624101816
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Konferensbidrag (refereegranskat)abstract
- This paper presents a method for effcient creation of the aerodynamic database for the X-31 experimental aircraft, from low fidelity (Euler) and high fidelity (RANS) CFD. The challenge is to obtain good data for extreme flight conditions. A co-Kriging interpolation model for aerodynamic moments, forces and span loads is used, with an additional decision support system (DSS) using Proper Orthogonal Decomposition for data reduction.
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