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| 2. |
- Bérard, Adrien, et al.
(författare)
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CADac : A New Geometry Construction Tool for Aerospace Vehicle Pre-Design and Conceptual Design
- 2008
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Ingår i: 26th AIAA Applied Aerodynamics Conference. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- In view of a continuous increase of computer performance, it is nowadays feasable to use CFD (Computational Fluid Dynamics) analysis very early in the conceptual design stage, if not the pre-concept phase, of aircraft. This requires the generation of a CAD (Computer Aided Design) model suitable for CFD computations, which is a tedious and time consuming process because a disconnect exists between the geometrical definition required for a CAD model and the limited number of geometry related design parameters defined by the designer. An additional complication to this is the requirement of producing a closed and consistent CAD model suitable for problem setup of CFD computations. The CADac (CAD-aircraft) tool nils this gap by automating the generation of closed and consistent CAD models via the implementation of a parameterized approach to conceptual design. CADac enables therefore to use CFD earlier and to use tools with inter-laced fidelity at the conceptual design phase.
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| 4. |
- Bérard, Adrien, 1981-
(författare)
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Method Development for Computer Aided Engineering for Aircraft Conceptual Design
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents the work done to implement new computational tools and methods dedicated to aircraft conceptual design sizing and optimization. These tools have been exercised on different aircraft concepts in order to validate them and assess their relevance and applicability to practical cases. First, a geometry construction protocol has been developed. It is indeed essential to have a geometry description that supports the derivation of all discretizations and idealizations used by the different analysis modules (aerodynamics, weights and balance, stability and control, etc.) for which an aircraft concept is evaluated. The geometry should also be intuitive to the user, general enough to describe a wide array of morphologies and suitable for optimization. All these conditions are fulfilled by an appropriate parameterization of the geometry. In addition, a tool named CADac (Computer Aided Design aircraft) has been created in order to produce automatically a closed and consistent CAD solid model of the designs under study. The produced CAD model is easily meshable and therefore high-fidelity Computational Fluid Dynamics (CFD) computations can be performed effortlessly without need for tedious and time-consuming post-CAD geometry repair.Second, an unsteady vortex-lattice method based on TORNADO has been implemented in order to enlarge to scope of flight conditions that can be analyzed. It has been validated satisfactorily for the sudden acceleration of a flat plate as well as for the static and dynamic derivatives of the Saab 105/SK 60.Finally, a methodology has been developed to compute quickly in a semi-empirical way the buffet envelope of new aircraft geometries at the conceptual stage. The parameters that demonstrate functional sensitivity to buffet onset have been identified and their relative effect quantified. The method uses a combination of simple sweep theory and fractional change theory as well as the buffet onset of a seed aircraft or a provided generic buffet onset to estimate the buffet envelope of any target geometry. The method proves to be flexible and robust enough to predict within mainly 5% (and in any case 9%) the buffet onset for a wide variety of aircrafts, from regional turboprop to long-haul wide body or high-speed business jets.This work was done within the 6th European framework project SimSAC (Simulating Stability And Control) whose task is to create a multidisciplinary simulation environment named CEASIOM (Computerized Environment for Aircraft Synthesis and Integrated Optimization Methods), oriented toward stability and control and specially suited for aircraft conceptual design sizing and optimization.
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| 5. |
- Böhnke, D., et al.
(författare)
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Towards a collaborative and integrated set of open tools for aircraft design
- 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 (AIAA).
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Konferensbidrag (refereegranskat)abstract
- A third generation Multi-Disciplinary Analysis & Optimization setup includes the collaboration of a distributed team of disciplinary experts and their respective anylsis tool to perform aircraft design. The integration of these tools can be eased by the application of open source software leaving more resources for the actual design task. Within the scope of this paper three open tools for aircraft design (OpenVSP, CEASIOM and VAMPzero) are introduced and integrated via a common namespace (CPACS). A design study on a two-engine transport aircraft is set up as an exemplary workflow.
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| 6. |
- Cavagna, L., et al.
(författare)
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A Fast MDO tool for Aeroelastic Optimization in Aircraft Conceptual Design
- 2008
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a design tool based on computational methods for the aero-structural analysis and optimization of aircraft layouts at the conceptual design stage. The whole methodology is based upon the integration of geometry construction, aerodynamic and structural analysis codes that combine depictive, computational, analytical, and semiempirical methods, validated in an aircraft design environment. The two primary modules are presented: CADac (Computer Aided Design Aircraft) for parametric geometry handling and NeoCASS (Next generation Conceptual Aero-Structural Sizing Suite) for structural sizing and numerical aeroelastic analysis. The aero-structural numerical kernel enables the creation of efficient low-order, high fidelity models which makes particularly suitable to be succesfully used within an MDO framework to drive the optimization tool into the most appropriate direction. Indeed, solving adverse aeroelastic issues like divergence, control surfaces reversal, flutter, increased drag at cruise speed due to structural deformability may require considerable changes in the structural design, limitations in flight envelope or weight penalties. The late discovery of this type of issues may result in significant cost increases and, in some cases, it may even require to actually close the project. In order to overcome the insurgence of these issues, the influence of deformability on flight and handling performances, on structural weight and on design costs needs to be taken into account as early as possible in the design process.
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| 7. |
- Cella, U., et al.
(författare)
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Sensitivity to physical and numerical modeling in Navier-Stokes simulations
- 2000
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Ingår i: Journal of Aerospace Engineering. - 0893-1321 .- 1943-5525. ; 13:2, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- Navier-Stokes Multiblock code solves the fully coupled system of equations simultaneously using a cell-centered finite-volume approach. This note assesses the sensitivity to some turbulence models and numerical schemes implemented in Navier-Stokes Multiblock when computing two test cases in standard mode, i.e., without tuning the code to these two cases. The cases are (1) subsonic flow around the MS(1)-0313 airfoil, and (2) transonic flow around the ONERA M6 wing, using various combinations of models (algebraic Baldwin-Lomax or Granville, one-equation Spalart-Allmaras, or the two-equation k - epsilon model of Chien) together with a numerical scheme of either the second-order central or third-order Roe upwind type.
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| 8. |
- Crippa, Simone, 1980-
(författare)
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Accurate physical and numerical modeling of complex vortex phenomena over delta wings
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With this contribution to the AVT-113/VFE-2 task group it was possible to prove the feasibility of high Reynolds number CFD computations to resolve and thus better understand the peculiar dual vortex system encountered on the VFE-2 blunt leading edge delta wing. Initial investigations into this phenomenon seemed to undermine the hypothesis, that the formation of the inner vortex system relies on the laminar state of the boundary layer at separation onset. As a result of this research, this initial hypothesis had to be expanded to account also for high Reynolds number cases, where a laminar boundary layer status at separation onset could be excluded. Furthermore, the data published in the same context shows evidence of secondary separation under the inner primary vortex. This further supports the supposition of a different generation mechanism of the inner vortical system other than a pure development out of a possibly laminar separation bubble. The unsteady computations performed on numerical grids with different levels of refinement led furthermore to the establishment of internal guidelines specific to the DES approach.
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| 9. |
- Crippa, Simone, 1980-
(författare)
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Advances in vortical flow prediction methods for design of delta-winged aircraft
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis covers the field of vortex-flow dominated external aerodynamics. As part of the contribution to the AVT-113 task group it was possible to prove the feasibility of high Reynolds number CFD computations to resolve and thus better understand the peculiar dual vortex system encountered on the VFE-2 blunt leading edge delta wing at low to moderate incidences. Initial investigations into this phenomenon seemed to undermine the hypothesis, that the formation of the inner vortex system depends on the laminar/turbulent state of the boundary layer at separation onset. As a result of this research, the initial hypothesis had to be expanded to account also for high Reynolds number cases, where a laminar boundary layer at separation onset can be excluded. In addition, unsteady transonic computations are used to shed light on a highly non-linear phenomenon encountered at high angles of incidence. At certain conditions, the increase of the incidence by a single degree leads to a sudden movement of the vortex breakdown location from the trailing edge to mid-chord. The lessons learned from the contribution to the VFE-2 facet are furthermore used to prove the technology readiness level of the tools within the second facet of AVT-113, the Cranked Arrow Wing Aerodynamics Project International (CAWAPI). The platform for this investigation, the F-16XL aircraft, experiences at high transonic speeds and low incidence a complex interaction between the leading edge vortex and a strong, mid-chord shock wave. A synergetic effect of VFE-2 with a further project, the Environmentally friendly High Speed Aircraft (HISAC), is also presented in this thesis. Reynolds number dependence is documented in respect to leading edge vortex formation of the wing planform for a reference HISAC configuration. Furthermore, proof is found for a similar dual vortex system as for the VFE-2 blunt leading edge configuration.
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