| 1. |
- Bérard, Adrien, et al.
(author)
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CADac : A New Geometry Construction Tool for Aerospace Vehicle Pre-Design and Conceptual Design
- 2008
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In: 26th AIAA Applied Aerodynamics Conference. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
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Conference paper (peer-reviewed)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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| 2. |
- Bérard, Adrien, et al.
(author)
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Conceptual Design Prediction of the Buffet Envelope of Transport Aircraft
- 2009
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In: Journal of Aircraft. - : American Institute of Aeronautics and Astronautics (AIAA). - 0021-8669 .- 1533-3868. ; 46:5, s. 1593-1606
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Journal article (peer-reviewed)abstract
- This paper describes a methodology that inexpensively predicts the buffet envelope of new transport airplane wing geometries at the conceptual design stage. The parameters that demonstrate a strong functional sensitivity to buffet onset were identified and their relative effect was quantified. To estimate the buffet envelope of any target aircraft geometry, the method uses fractional change transformations in consort with a generic reference buffet onset curve provided by the authors or the buffet onset of a known seed airplane. The explicit design variables required to perform buffet onset prediction are those describing the wing planform and the wingtip section. The mutually exclusive nature of the method's analytical construct provides considerable freedom in deciding the scope of free-design-variable complexity. The method has been shown to be adequately robust and flexible enough to deal with a wide variety of transport airplane designs. For the example transport airplanes considered, irrespective of aircraft morphology and en route flight phase, the relative error in prediction was found to be mostly within +/-5.0%, with occasional excursions not exceeding a +/-9.0% bandwidth. The standard error of estimate for the lift coefficient at 1.0 g buffet onset at a given Mach number was calculated to be 0.0262.
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| 3. |
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| 4. |
- Bérard, Adrien, et al.
(author)
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Development and validation of a next-generation conceptual aero-structural sizing suite
- 2008
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In: ICAS Secr. - Int. Counc. Aeronaut. Sci. ICAS. - 9781605607153 ; , s. 1718-1727
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Conference paper (peer-reviewed)abstract
- An overview of a novel variable-fidelity aerostructural computational suite targeted for prediction at the conceptual design phase is presented herein. The computational suite consists of two primary modules known as CADac (Computer Aided Design Aircraft) and NeoCASS (Next generation Conceptual Aero-Structural Sizing Suite). The 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 aerodynamics sub-space is analyzed using methods based upon a Vortex-Lattice Method used to examine large structural deformations, a Doublet Lattice Method in order to predict flutter boundaries in the subsonic speed regime, and, an Euler based method to cater for identification of flutter points in the transonic regime. A quasi-analytical method that provides accurate weights estimation and refined prediction of airframe moments of inertia data has also been introduced, thus facilitating a more comprehensive investigation of the quasi-static aeroelastic problem. To illustrate the new computational system capabilities, the methodology was applied to a complete flexible structural model of the B747-100 transport aircraft. The quasianalytical weight prediction of the NeoCASS suite was found to generate an accuracy of less than 0.5% error compared to published results.
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| 5. |
- Bérard, Adrien, 1981-
(author)
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Method Development for Computer Aided Engineering for Aircraft Conceptual Design
- 2008
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Licentiate thesis (other academic/artistic)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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| 6. |
- Cavagna, L., et al.
(author)
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A Fast MDO tool for Aeroelastic Optimization in Aircraft Conceptual Design
- 2008
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Conference paper (other academic/artistic)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. |
- Ghoreyshi, M., et al.
(author)
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Aerodynamic modelling for flight dynamics analysis of conceptual aircraft designs
- 2009
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In: 27th AIAA Applied Aerodynamics Conference.
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Conference paper (peer-reviewed)abstract
- Physics based simulation in conceptual design is widely seen as a way of increasing the information about designs, thus helping with the avoidance of unanticipated problems as the design is refined. This paper reports on an effort to assess the use of CFD level aerodynamics for the development of tables for flight dynamics analysis at the conceptual stage. A number of aerodynamic data sources are used with sampling and data fusion to allow the efficient generation of the tables. A refined design passenger jet wind tunnel model is used as a test case, and three simplified conceptual versions of this geometry are generated. The influence of geometry approximations and modelling influences are evaluated to assess the usefulness of CFD for this application. Finally, the aerodynamic differences are assessed in terms of basic longitudinal flight dynamics analysis.
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