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Method Development for Computer Aided Engineering for Aircraft Conceptual Design
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , ix, 37 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2008-57
Keyword [en]
Aircraft conceptual design, Computer Aided Design (CAD), buffet onset, unsteady vortex-lattice method
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9240ISBN: 978-91-7415-137-4 (print)OAI: oai:DiVA.org:kth-9240DiVA: diva2:37692
Presentation
2008-10-27, S 40, Teknikringen 8, Stockholm, 15:15 (English)
Opponent
Supervisors
Projects
SimSAC
Note
QC 20101104Available from: 2008-10-14 Created: 2008-10-10 Last updated: 2010-11-04Bibliographically approved
List of papers
1. CADac: A New Geometry Construction Tool for Aerospace Vehicle Pre-Design and Conceptual Design
Open this publication in new window or tab >>CADac: A New Geometry Construction Tool for Aerospace Vehicle Pre-Design and Conceptual Design
2008 (English)In: 26th AIAA Applied Aerodynamics Conference: Honolulu, HI: 18 August 2008 through 21 August 2008, 2008Conference paper, Published paper (Refereed)
Abstract [en]

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.

Series
Collection of Technical Papers - AIAA Applied Aerodynamics Conference, ISSN 1048-5953
Keyword
CAD modeling, CFD computations, Aerodynamics, Aerospace vehicles, Air, Aircraft, Aircraft models, Computational fluid dynamics, Computational geometry, Computer networks, Conceptual design, Design, Dynamics, Fluid dynamics, Fluid mechanics, Gas dynamics, Multi agent systems, Process engineering, Transonic aerodynamics
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9276 (URN)2-s2.0-77957759649 (Scopus ID)
Note
QC 20101104Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2010-11-04Bibliographically approved
2. A Fast MDO tool for Aeroelastic Optimization in Aircraft Conceptual Design
Open this publication in new window or tab >>A Fast MDO tool for Aeroelastic Optimization in Aircraft Conceptual Design
Show others...
2008 (English)Conference paper, Published paper (Other academic)
Abstract [en]

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.

National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9277 (URN)2-s2.0-78049525231 (Scopus ID)
Conference
12th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference
Note
QC 20101104Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2010-11-04Bibliographically approved
3. Development and Implementation of Aerodynamic Analysis Methods for Aircraft Conceptual Design
Open this publication in new window or tab >>Development and Implementation of Aerodynamic Analysis Methods for Aircraft Conceptual Design
2007 (English)Conference paper, Published paper (Other academic)
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9278 (URN)
Conference
CASI AERO 2007 Aircraft Design and Development Symposium
Note
QC 20101104Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2010-11-04Bibliographically approved
4. Conceptual Design Prediction of the Buffet Envelope of Transport Aircraft
Open this publication in new window or tab >>Conceptual Design Prediction of the Buffet Envelope of Transport Aircraft
2009 (English)In: Journal of Aircraft, ISSN 0021-8669, E-ISSN 1533-3868, Vol. 46, no 5, 1593-1606 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Aircraft geometries, Design variables, En-route, Flight phase, Functional sensitivities, Lift coefficient, Relative errors, Standard errors, Transport airplane, Wing planforms, Mach number, Transport aircraft, Wings
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9279 (URN)10.2514/1.41367 (DOI)000270749600014 ()2-s2.0-73649108600 (Scopus ID)
Note
QC 20101104 Uppdaterad från submitted till published (20101104).Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2017-12-07Bibliographically approved

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