| 1. |
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| 2. |
- Eller, David, et al.
(author)
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Implementation and evaluation of automated tetrahedral-prismatic mesh generation software
- 2015
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In: Computer-Aided Design. - : Elsevier. - 0010-4485 .- 1879-2685.
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Journal article (peer-reviewed)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, where constrained global optimization of the envelope is employed. Once a well-shaped envelope is thus obtained, a semi-structured layer of pentahedral elements is extruded between wall and envelope surface. Satisfactory mesh quality is demonstrated by comparing solutions obtained using the new meshes with reference data computed on high-quality advancing-front grids. Mesh generation time is shown to be substantially smaller than with many 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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| 3. |
- Goetzendorf-Grabowski, Tomas, et al.
(author)
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Coupling Adaptive-Fidelity CFD with S&C Analysis to Predict Flying Qualities
- 2009
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In: 27th AIAA Applied Aerodynamics Conference.
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Conference paper (peer-reviewed)abstract
- CEASIOM, the Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods, is a framework tool that integrates discipline-specific tools for conceptual design. At this early stage of the design it is very useful to be able to predict the °ying and handling qualities of this design. In order to do this, the aerodynamic database needs to be computed for the configuration being studied which then has to be coupled to the stability and control tools to carry out the analysis. This paper describes how the adaptive-fidelity CFD module of CEASIOM computes the aerodynamic dataset of an air craft configuration, and how that dataset is analyzed by the SDSA module to determine the °ying qualities of the aircraft. These predicted °ying qualities are then compared with the °ight-test data of the Ranger 2000 trainer aircraft in order to verify the goodness of the overall approach.
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| 4. |
- Mendenhall, M.R., et al.
(author)
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Comparing and benchmarking engineering methods for the prediction of X-31 aerodynamics
- 2012
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In: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638 .- 1626-3219. ; 20:1, s. 12-20
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Journal article (peer-reviewed)abstract
- A number of useful engineering methods are available for fast and economic estimates of the aerodynamic characteristics of complex flight vehicles. This article investigates the application of three specific engineering methods to the X-31 fighter configuration, and CFD, wind tunnel, and flight test data are used for comparison and evaluation purposes. The emphasis is on static longitudinal stability aspects up to high angles of attack; however, selected asymmetric and unsteady effects are considered. Results from the engineering methods are in good agreement with experiment and CFD for angles of attack up to 15° for most cases and higher angles for some cases. Results for pitching moment are in good agreement with CFD, but many of the nonlinear characteristics of the airplane are not predicted by the engineering methods. The quality of the longitudinal stability results is discussed in terms of the prediction of the center of pressure on the vehicle. The results provide improved understanding of the continued usefulness of engineering methods as an analysis tool during the design phase and into the flight test diagnostic phase of a new aircraft.
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| 5. |
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| 6. |
- Tomac, Maximilian
(author)
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Adaptive-fidelity CFD for predicting flying qualities in preliminary aircraft design
- 2011
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Licentiate thesis (other academic/artistic)abstract
- To reduce development cost and to avoid late design fixes in aircraft design, methods that are fast and economic in estimating the aerodynamic characteristics of complex flight vehicles at the preliminary design stage are desired. This work and thesis focus on the adaptive-fidelity CFD approach, with emphasis on the high end of the CFD tools available today. The core idea of the method is to use computationally cheap modeling in the part of the flight envelope where it is applicable. When the complexity in the flow field increases more details and realism is included in the mathematical model, at a computationally higher cost. A typical case where this would be required could be at the border of the flight envelope, where flow phenomena such as shocks, flow separation, and interacting vortex systems could occur. Since the number of cases needed to resolve the flight envelope could be in the order of ten thousands automation is required. The bottlenecks are the discretization of the fluid volume and evaluation of raw CFD data and post processing of the data. These issues are also discussed in this work. The method has been tested on two real flying aircraft, the X-31 delta-winged aircraft with vector thrust, and the Ranger 2000 Jet trainer, as well as on the SACCON preliminary wing-body UCAV design. The results provide improved understanding of the usefulness of this method as an analysis tool during the preliminary design phase all the way into the flight test diagnostic phase of a new aircraft.
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| 7. |
- Tomac, Maximilian, et al.
(author)
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CFD study of vortex separation phenomena on blunt diamond wing
- 2015
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In: 53rd AIAA Aerospace Sciences Meeting. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624103438
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Conference paper (peer-reviewed)abstract
- The details of how a vortex lifts off a blunt swept leading edge are not so well understood, and this paper undertakes a comprehensive CFD study of the phenomena. Current day experience shows that the location for the start of the vortex depends on the grid resolution of the numerical solution and the physical modeling used to account for the turbulence in the flow. In this work multiple levels of grid refinement, together with ap- propriate adaptation of the grids, are carried out to the extent that stabilizes the location of the separation. Various turbulence models are also used in combination with the grid sequencing showing a strong effect on vortex separation position due to chosen turbulence model.
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| 8. |
- Tomac, Maximilian, et al.
(author)
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Comparing & benchmarking engineering methods on the prediction of X-31 aerodynamics
- 2010
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In: 28th AIAA Applied Aerodynamics Conference. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781617389269 ; , s. 2010-4694-
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Conference paper (peer-reviewed)abstract
- NATO RTO-AVT-161 is an assessment of Stability and Control Prediction Methods for NATO Air and Sea Vehicles. Though the assessment includes the use of advanced CFD methods, a number of useful engineering methods are available for fast and economic estimates of the aerodynamic characteristics of complex flight vehicles. The objective of this paper is to investigate the use of three specific engineering methods on the X-31 fighter configuration for which CFD, wind tunnel, and flight test data are available for comparison and evaluation purposes. The emphasis is on static longitudinal stability aspects up to high angles of attack; however, selected asymmetric and unsteady effects are considered. Results from the engineering methods are in good agreement with experiment and CFD for angles of attack up to 15 degrees for most cases and higher angles for some cases. Results for pitching moment are in good agreement with CFD, but many of the nonlinear characteristics of the airplane are not predicted by the engineering methods. The quality of the longitudinal stability results is discussed in terms of the prediction of the center of pressure on the vehicle. The results provide improved understanding of the continued usefulness of engineering methods as an analysis tool during the design phase and into the flight test diagnostic phase of a new aircraft.
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| 9. |
- Tomac, Maximilian, et al.
(author)
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Creation of aerodynamic database for the X-31
- 2010
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In: 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781600867392 ; , s. 2010-0501-
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Conference paper (peer-reviewed)abstract
- Adaptive fidelity computional fluid dynamics (CFD) uses CFD tools spanning from vortexlattice methods codes to more advanced inviscid Euler solvers and finally URANS (Unsteady Reynolds Averaged Navier Stokes) CFD solvers. At the high end the automatization process is no longer a simple straight forward task, for this purpose a script-driven tool has been developed for integration into the multi-fidelity framework CEASIOM developed in the SimSAC project. The scripting technologies to prepare, conduct, post-process and collect aerodynamic forces & moments into the aero-dataset. The tool together with the CEASIOM framework has been applied to the X-31 to create an aerodynamic dataset that is then analyzed by the stability & control tool SDSA to assess the modes of motion inherent in the dataset.
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| 10. |
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